1.xx.01 - Segger Microcontroller

embOS &

embOS-MPU

Real-Time Operating System

User Guide & Reference Manual

Document: UM01001

Software Version: 5.02

Revision: 0

Date: June 26, 2018

A product of SEGGER Microcontroller GmbH

www.segger.com

Disclaimer

Specifications written in this document are believed to be accurate, but are not guaranteed to

be entirely free of error. The information in this manual is subject to change for functional or

performance improvements without notice. Please make sure your manual is the latest edition.

While the information herein is assumed to be accurate, SEGGER Microcontroller GmbH (SEG-

GER) assumes no responsibility for any errors or omissions. SEGGER makes and you receive no

warranties or conditions, express, implied, statutory or in any communication with you. SEGGER

specifically disclaims any implied warranty of merchantability or fitness for a particular purpose.

You may not extract portions of this manual or modify the PDF file in any way without the prior

written permission of SEGGER. The software described in this document is furnished under a

license and may only be used or copied in accordance with the terms of such a license.

Trademarks

Names mentioned in this manual may be trademarks of their respective companies.

Brand and product names are trademarks or registered trademarks of their respective holders.

Contact address

SEGGER Microcontroller GmbH

In den Weiden 11

D-40721 Hilden

Germany

Tel. +49 2103-2878-0

Fax. +49 2103-2878-28

E-mail: support@segger.com

Internet: www.segger.com

Manual versions

This manual describes the current software version. If you find an error in the manual or a

problem in the software, please inform us and we will try to assist you as soon as possible.

Print date: June 26, 2018

Software Revision Date By Description

5.02 0 180626 TS New API function OS_STAT_AddLoadMeasurementEx().

Minor spelling & wording corrections.

5.00 1 180524 TS OS_TASK_Delay() parameter description corrected.

TimeOut parameter description added where necessary.

5.00 0 180508 TS

New API names.

Chapter “Debugging” updated.

Minor spelling & wording corrections.

4.40 0 171220 MC

Introductory description in chapter “Software timers” expanded.

Description of limitations in chapter “Mailboxes” corrected.

Description of limitations in chapter “Queues” added.

Description of embOS trial edition in chapter “Shipment” updated.

Decription of OS_WD_Config() updated for change in parameters.

List of error codes in chapter “Debugging” updated.

Minor spelling & wording corrections.

4.38 1 170928 MC Minor spelling & wording corrections.

4.38 0 170919 TS

First version generated with emDoc.

New function in chapter “Tasks” added:

• OS_SetDefaultTaskStartHook()

New functions in chapter “Debugging” added:

• OS_SetObjName()

• OS_GetObjName()

Minor corrections/updates.

4.36 0 170711 TS

New library mode OS_LIBMODE_SAFE added in chapter “Basic Concepts”.

New functions in chapter “Stacks” added:

• OS_GetStackCheckLimit()

• OS_SetStackCheckLimit()

New functions in chapter “MPU” added:

• OS_MPU_AddSanityCheckBuffer()

• OS_MPU_SanityCheck()

Chapter “Source Code” updated.

New functions in chapter “Task Routines” added:

• OS_Config_Stop()

• OS_Stop()

Minor corrections/updates

4.34 0 170308 TS

New functions in chapter “Event Objects” added:

• OS_EVENT_GetMaskMode()

• OS_EVENT_SetMaskMode()

4.32 0 170105 RH/TS

Chapter “Watchdog” added.

New functions in chapter “Event Objects” added:

• OS_EVENT_GetMask()

• OS_EVENT_SetMask()

• OS_EVENT_WaitMask()

• OS_EVENT_WaitMaskTimed()

New functions in chapter “Mailboxes” added:

• OS_PutMailTimed()

• OS_PutMailTimed1()

4.30 0 161130 MC/TS

Chapter “Basic Concepts”, “Time Measurement”, “MPU”, “Profiling” and

“Updates” updated.

Chapters, “System Tick”, “Low Power Support”, “Configuration (BSP)”

updated and re-structured.

Chapter “Resource Semaphores” updated.

4.26 0 160907 RH Chapter “embOSView”, “Interrupts” and “MPU” updated.

Minor corrections/updates.

4.24 0 160628 MC Chapter “Multi-core Support” added.

Chapter “Debugging” updated.

4.22 0 160525 MC

New functions in chapter “Queues” added:

• OS_Q_PutEx()

• OS_Q_PutBlockedEx()

Software Revision Date By Description

• OS_Q_PutTimedEx()

4.20 0 160421 TS Chapter “MPU - Memory Protection” added.

OS_AddExtendTaskContext() added.

4.16 0 160210 TS Minor corrections/updates

4.14a 0 160115 TS Minor corrections/updates

4.14 0 151029 TS

Chapter “Interrupts” updated.

Description of new API function OS_SetDefaultTaskContextExten-

sion() added.

Chapter “System Variables”: embOS info routines added.

Chapter “Shipment” updated.

Chapter “Low Power Support” updated.

Chapter “Interrupts”: Description of

• OS_INT_PRIO_PRESERVE() and

• OS_INT_PRIO_RESTORE() added.

Chapter “Software Timerss”: Description of

• OS_TriggerTimer() and

• OS_TriggerTimerEx() added.

4.12b 0 150922 TS Update to latest software version.

4.12a 0 150916 TS Description of API function OS_InInterrupt() added.

4.12 0 150715 TS

New funtions in chapter “Mailboxes” added:

• OS_Mail_GetPtr()

• OS_Mail_getPtrCond()

• OS_Mail_Purge()

Chapter “Debugging” with new error codes updated.

4.10b 1 150703 MC Minor spelling and wording corrections.

4.10b 0 150527 TS

Minor spelling and wording corrections.

Chapter “Source Code of Kernel and Library” updated.

New chapter “embOS Shipment”.

New chapter “Update”.

New chapter “Low Power Support”.

4.10a 0 150519 MC Minow spelling and wording corrections.

Chapter “embOSView”: added JTAG Chain configuration.

4.10 0 150430 TS Chapter “embOSView” updated.

4.06b 0 150324 MC Minow spelling and wording corrections.

4.06a 0 150318 MC Minow spelling and wording corrections.

4.06 0 150312 TS Updated to latest software version.

4.04a 0 141201 TS Updated to latest software version.

4.04 0 141112 TS

Chapter “Tasks”

• Task priority description updated.

Chapter “Debugging”

• New error number

4.02a 0 140918 TS Update to latest software version.

Minor corrections.

4.02 0 140818 TS

New functions in chapter “Time Measurement” added:

• OS_Config_SysTimer()

• OS_GetTime_us()

• OS_GetTime_us64()

4.00a 0 140723 TS

New functions added in chapter “System Tick”:

• OS_StopTicklesMode()

New functions added in chapter “Profiling”:

• OS_STAT_Start()

• OS_STAT_Stop()

• OS_STAT_GetTaskExecTime()

4.00 0 140606 TS Tickless support added.

3.90a 0 140410 AW Software-Update, OS_TerminateTask() modified / corrected.

3.90 1 140312 SC Added cross-references to the API-lists.

3.90 0 140303 AW

New functions to globally enable / disable Interrupts:

• OS_INTERRUPT_MaskGlobal()

• OS_INTERRUPT_UnmaskGlobal()

Software Revision Date By Description

• OS_INTERRUPT_PreserveGlobal()

• OS_INTERRUPT_RestoreGlobal()

• OS_INTERRUPT_PreserveAndMaskGlobal()

3.88h 0 131220 AW

New functions added, chapter “System Tick”:

• OS_GetNumIdleTicks()

• OS_AdjustTime()

Chapter “System Variables”: Description of internal variable OS_Glob-

al.TimeDex corrected.

3.88g 1 131104 TS Corrections.

3.88g 0 131030 TS Update to latest software version.

3.88f 0 130922 TS Update to latest software version.

3.88e 0 130906 TS Update to latest software version.

3.88d 0 130904 AW Update to latest software version.

3.88c 0 130808 TS Update to latest software version.

3.88b 0 130528 TS Update to latest software version.

3.88a 0 130503 AW

Software update.

Event handling modified, the reset behaviour of events can be con-

trolled.

New functions added, chapter “Events”:

• OS_EVENT_CreateEx()

• OS_EVENT_SetResetMode()

• OS_EVENT_GetResetMode()

Mailboxes message size limits enlarged.

3.88 0 130219 TS Minor corrections.

3.86n 0 121210 AW/TS Update to latest software version.

3.86l 0 121122 AW

Software update.

OS_AddTickHook() function corrected.

Several functions modified to allow most of MISRA rule checks.

3.86k 0 121004 TS

Chapter “Queue”:

• OS_Q_GetMessageSize() and

• OS_Q_PeekPtr() added.

3.86i 0 120926 TS Update to latest software version.

3.86h 0 120906 AW Software update, OS_EVENT handling with timeout corrected.

3.86g 0 120806 AW

Software update, OS_RetriggerTimer() corrected.

Task events explained more in detail.

Additional software examples in the manual.

3.86f 0 120723 AW

Task event modified, default set to 32bit on 32bit CPUs.

Chapter 4:

• New API function OS_AddOnTerminateHook()

• OS_ERR_TIMESLICE removed. A time slice value of zero is legal

when creating tasks.

3.86e 0 120529 AW

Update to latest software version with corrected functions:

• OS_GetSysStackBase()

• OS_GetSysStackSize()

• OS_GetSysStackSpace()

• OS_GetSysStackUsed()

• OS_GetIntStackBase()

• OS_GetIntStackSize()

• OS_GetIntStackSpace()

• OS_GetIntStackUsed()

could not be used in release builds of embOS.

Manual corrections:

• Several index entries corrected.

• OS_EnterRegion() described more in detail.

3.86d 0 120510 TS Update to latest software version.

3.86c 0 120508 TS Update to latest software version.

3.86b 0 120502 TS

Chapter “Mailbox”

• OS_PeekMail() added.

Chapter “Support” added.

Chapter “Debugging”:

Software Revision Date By Description

• Application defined error codes added.

3.86 0 120323 AW

Timeout handling for waitable objects modified. A timeout will be re-

turned from the waiting function, when the object was not available

during the timeout time. Previous implementation of timeout functions

might have returned a signaled state when the object was signaled af-

ter the timeout when the calling task was blocked for a longer period by

higher priorized tasks

Modified functions:

• OS_UseTimed()

• OS_WaitCSemaTimed()

• OS_GetMailTimed()

• OS_WaitMailTimed()

• OS_Q_GetPtrTimed()

• OS_EVENT_WaitTimed()

• OS_MEMF_AllocTimed()

New chapter “Extending the Task Context” added.

New functions added and described in the manual:

• OS_GetTaskName()

• OS_GetTimeSliceRem()

Handling of queues described more in detail:

• OS_Q_GetPtr()

• OS_Q_GetPtrCond()

• OS_Q_GetPtrTimed()

• OS_Q_Purge()

Chapter “Priority Inversion / Inheritance” updated.

Function names OS_Timing_Start() and OS_Timing_End() corrected in

the API table.

3.84c 1 120130 AW/TS

Since version 3.822 of embOS, all pointer parameter pointing to objects

which were not modified by the function were declared as const, but the

manual was not updated accordingly.

The prototype descriptions of the following API functions are corrected

now:

• OS_GetTimerValue()

• OS_GetTimerStatus()

• OS_GetTimerPeriod()

• OS_GetSemaValue()

• OS_GetResourceOwner()

• OS_Q_IsInUse()

• OS_Q_GetMessageCnt()

• OS_IsTask()

• OS_GetEventsOccured()

• OS_GetCSemaValue()

• OS_TICK_RemoveHook()

• OS_MEMF_IsInPool()

• OS_MEMF_GetMaxUsed()

• OS_MEMF_GetNumBlocks()

• OS_MEMF_GetBlockSize()

• OS_GetSuspendCnt()

• OS_GetPriority()

• OS_EVENT_Get()

• OS_Timing_Getus()

Chapter “Preface”:

• Segger Logo replaced

Chapter “Mailbox”:

• OS_CREATEMB() changed to OS_CreateMB()

Chapter “Queues”:

• Typos corrected

3.84c 0 120104 TS Chapter “Events”:

• Return value of OS_EVENT_WaitTimed() explained in more detail

3.84b 0 111221 TS Chapter “Queues”:

• OS_Q_PutBlocked() added

3.84a 0 111207 TS General updates and corrections.

3.84 0 110927 TS

Chapter “Stacks”:

• OS_GetSysStackBase() added

• OS_GetSysStackSize() added

• OS_GetSysStackUsed() added

• OS_GetSysStackSpace() added

• OS_GetIntStackBase() added

• OS_GetIntStackSize() added

• OS_GetIntStackUsed() added

Software Revision Date By Description

• OS_GetIntStackSpace() added

3.82x 0 110829 TS Chapter “Debugging”:

• New error code “OS_ERR_REGIONCNT” added

3.82w 0 110812 TS New embOS generic sources.

Chapter “Debugging” updated.

3.82v 0 110715 AW OS_Terminate() renamed to OS_TerminateTask().

3.82u 0 110630 TS New embOS generic sources.

Chapter 13: Fixed size memory pools modified.

3.82t 0 110503 TS New embOS generic sources.

Trial time limitation increased.

3.82s 0 110318 AW

Chapter “Timer” API functions table corrected.

All functions can be called from main(), task, ISR or Timer.

Chapter 6: OS_UseTimed() added.

Chapter 9: OS_Q_IsInUse() added.

3.82p 0 110112 AW

Chapter “Mailboxes”:

• OS_PutMail()

• OS_PutMailCond()

• OS_PutMailFront()

• OS_PutMailFrontCond()

parameter decklaration changed.

Chapter 4.3 API functions table corrected.

OS_Suspend() cannot be called from ISR or Timer.

3.82o 0 110104 AW Chapter “Mailboxes”:

• OS_WaitMailTimed() added

3.82n 0 101206 AW

Chapter “Taskroutines”:

• OS_ResumeAllSuspendedTasks() added

• OS_SetInitialSuspendCnt() added

• OS_SuspendAllTasks() added

Chapter “Time Measurement”:

• Description of OS_GetTime32() corrected

Chapter “List of Error Codes”:

• New error codes added

3.82k 0 100927 TS

Chapter “Taskroutines”:

• OS_Delayus() added

• OS_Q_Delete() added

3.82i 0 100917 TS General updates and corrections

3.82h 0 100621 AW

Chapter “Event Objects”:

• Samples added

Chapter “Configuration of Target System”:

• Detailed description of OS_Idle() added

3.82f 1 100505 TS

Chapter “Profiling” added

Chapter “System Tick”:

• OS_TickHandleNoHook() added

3.82f 0 100419 AW

Chapter “Tasks”:

• OS_IsRunning() added

• Description of OS_Start() added

3.82e 0 100309 TS

Chapter “Working with embOS - Recommendations” added.

Chapter “Basics”:

• Priority inversion image added

Chapter “Interrupt”:

• subchapter “Using OS functions from high priority interrupts” added

Added text at chapter 22 “Performance and resource usage”

3.82 0 090922 TS

API function overview now contains information about allowed context of

cuntion usage (main, task, ISR or timer)

TOC format corrected

3.80 0 090612 AW Scheduler optimized for higher task switching speed.

3.62c 0 080903 SK

Chapter structure updated.

Chapter “Interrupts”:

• OS_LeaveNestableInterruptNoSwitch() removed

• OS_LeaveInterruptNoSwitch() removed

Chapter “System Tick”:

• OS_TICK_Config() added

3.60 2 080722 SK Contact address updated.

Software Revision Date By Description

3.60 1 080617 SK

General updates.

Chapter “Mailboxes”:

• OS_GetMailCond() / OS_GetMailCond1() corrected

3.60 0 080117 OO General updates.

Chapter “System Tick” added.

3.52 1 071026 AW Chapter “Task Routines”:

• OS_SetTaskName() added

3.52 0 070824 OO

Chapter “Task Routines”:

• OS_ExtendTaskContext() added

Chapter “Interrupts”:

• Updated

• OS_CallISR() added

• OS_CallNestableISR() added

3.50c 0 070814 AW Chapter “List of Libraries” updated, XR library type added.

3.40c 3 070716 OO Chapter “Performance and Resource Usage” updated.

3.40c 2 070625 SK

Chapter “Debugging”, error codes updated:

• OS_ERR_ISR_INDEX added

• OS_ERR_ISR_VECTOR added

• OS_ERR_RESOURCE_OWNER added

• OS_ERR_CSEMA_OVERFLOW added

Chapter “Task Routines”:

• OS_Yield() added

Chapter “Counting Semaphores” updated

• OS_SignalCSema(), additional information adjusted

Chapter “Performance and Resource Usage” updated:

• Minor changes in wording.

3.40a 1 070608 SK

Chapter “Counting Semaphores” updated:

• OS_SetCSemaValue() added

• OS_CreateCSema(): Data type of parameter InitValue changed from

unsigned char to unsigned int

• OS_SignalCSemaMax(): Data type of parameter MaxValue changed

from unsigned char to unsigned int

• OS_SignalCSema(): Additional information updated

3.40 0 070516 SK

Chapter “Performance and Resource Usage” added.

Chapter “Configuration of your Target System (RTOSInit.c)” renamed to

“Configuration of your Target System”.

Chapter “STOP/WAIT/IDLE modes” moved into chapter “Configuration of

your Target System”.

Chapter “Time-related Routines” renames to “Time Measurement”.

3.32o 9 070422 SK Chapter 4: OS_CREATETIMER_EX(), additional information corrected.

3.32m 8 070402 AW Chapter 4: Extended timer added.

Chapter 8: API overview corrected, OS_Q_GetMessageCount()

3.32j 7 070216 AW Chapter 6: OS_CSemaRequest() function added.

3.32e 6 061220 SK About: Company description added.

Some minor formatting changes.

3.32e 5 061107 AW Chapter 7: OS_GetMessageCnt() return value corrected to unsigned int.

3.32d 4 061106 AW Chapter 8: OS_Q_GetPtrTimed() function added.

3.32a 3 061012 AW

Chapter 3: OS_CreateTaskEx() function, description of parameter pCon-

text corrected.

Chapter 3: OS_CreateTaskEx() function, type of parameter TimeSlice

corrected.

Chapter 3: OS_CreateTask() function, type of parameter TimeSlice cor-

rected.

Chapter 9: OS_GetEventOccured() renamed to OS_GetEventsOc-

cured().

Chapter 10: OS_EVENT_WaitTimed() added.

3.32a 2 060804 AW Chapter 3: OS_CREATETASK_EX() function added.

Chapter 3: OS_CreateTaskEx() function added.

3.32 1 060717 OO

Event objects introduced. Chapter 10 inserted which describes event ob-

jects.

Previous chapter “Events” renamed to “Task Events”.

3.30 1 060519 OO New software version.

Software Revision Date By Description

3.28 5 060223 OO All chapters: Added API tables.

Some minor changes.

3.28 4 051109 AW

Chapter 7: OS_SignalCSemaMax() function added.

Chapter 14: Explanation of interrupt latencies and high / low priorities

added.

3.28 3 050926 AW Chapter 6: OS_DeleteRSema() function added.

3.28 2 050707 AW Chapter 4: OS_GetSuspendCnt() function added.

3.28 1 050425 AW Version number changed to 3.28 to fit to current embOS version.

Chapter 18.1.2: Type return value of OS_GetTime32() corrected.

3.26 0 050209 AW

Chapter 4: OS_Terminate() modified due to new features of version

2.26.

Chapter 24: Source code version: additional compile time switches and

build process of libraries explained more in detail.

3.24 0 011115 AW Chapter 6: Some prototype declarations showed in OS_SEMA instead of

OS_RSEMA. Corrected.

3.22 1 040816 AW

Chapter 8: New Mailbox functions added

• OS_PutMailFront()

• OS_PutMailFront1()

• OS_PutMailFrontCond()

• OS_PutMailFrontCond1()

3.20 5 040621 RS/AW

Software timers: Maximum timeout values and OS_TIMER_MAX_TIME de-

scribed.

Chapter 14: Description of rules for interrupt handlers revised.

OS_LeaveNestableInterruptNoSwitch() added which was not de-

scribed before.

3.20 4 040329 AW

OS_CreateCSema() prototype declaration corrected. Return type is void.

OS_Q_GetMessageCnt() prototype declaration corrected.

OS_Q_Clear() function description added.

OS_MEMF_FreeBlock() prototype declaration corrected.

3.20 2 031128 AW OS_CREATEMB() Range for parameter MaxnofMsg corrected. Upper limit

is 65535, but was declared 65536 in previous manuals.

3.20 1 040831 AW Code samples modified: Task stacks defined as array of int, because

most CPUs require alignment of stakc on integer aligned addresses.

3.20 1 031016 AW

Chapter 4: Type of task priority parameter corrected to unsigned char.

Chapter 4: OS_DelayUntil(): Sample program modified.

Chapter 4: OS_Suspend() added.

Chapter 4: OS_Resume() added.

Chapter 5: OS_GetTimerValue(): Range of return value corrected.

Chapter 6: Sample program for usage of resource semaphores modified.

Chapter 6: OS_GetResourceOwner(): Type of return value corrected.

Chapter 8: OS_CREATEMB(): Types and valid range of parameter correct-

ed.

Chapter 8: OS_WaitMail() added

Chapter 10: OS_WaitEventTimed(): Range of timeout value specified.

3.12 1 021015 AW

Chapter 8: OS_GetMailTimed() added

Chapter 11 (Heap type memory management) inserted

Chapter 12 (Fixed block size memory pools) inserted

3.10 3

020926

020924

020910

Index and glossary revised.

Section 16.3 (Example) added to Chapter 16 (Time-related Routines).

Revised for language/grammar.

Version control table added.

Screenshots added: superloop, cooperative/preemptive multitasking,

nested interrupts, low-res nad hi-res measurement.

Section 1.3 (Typographic conventions) changed to table.

Section 3.2 added (Single-task system).

Section 3.8 merged with section 3.9 (How the OS gains control).

Chapter 4 (Configuration for your target system) moved to after Chapter

15 (System variables)

Chapter 16 (Time-related routines) added.

About this document

Assumptions

This document assumes that you already have a solid knowledge of the following:

• The software tools used for building your application (assembler, linker, C compiler).

• The C programming language.

• The target processor.

• DOS command line.

If you feel that your knowledge of C is not sufficient, we recommend The C Programming Lan-

guage by Kernighan and Richie (ISBN 0–13–1103628), which describes the standard in C pro-

gramming and, in newer editions, also covers the ANSI C standard.

How to use this manual

This manual explains all the functions and macros that the product offers. It assumes you have

a working knowledge of the C language. Knowledge of assembly programming is not required.

Typographic conventions for syntax

This manual uses the following typographic conventions:

Style Used for

Body Body text.

Keyword Text that you enter at the command prompt or that appears on

the display (that is system functions, file- or pathnames).

Parameter Parameters in API functions.

Sample Sample code in program examples.

Sample comment Comments in program examples.

Reference Reference to chapters, sections, tables and figures or other doc-

uments.

GUIElement Buttons, dialog boxes, menu names, menu commands.

Emphasis Very important sections.

Table of contents

1 Introduction and basic concepts ................................................................................. 17

1.1 What is embOS? .......................................................................................... 18

1.2 Tasks .......................................................................................................... 20

1.3 Single-task systems (superloop) .................................................................... 21

1.4 Multitasking systems .................................................................................... 23

1.5 Scheduling .................................................................................................. 25

1.6 Communication between tasks .......................................................................27

1.7 How task switching works ............................................................................. 28

1.8 Change of task status .................................................................................. 30

1.9 How the OS gains control ............................................................................. 31

1.10 Different builds of embOS ........................................................................... 32

1.11 Valid context for embOS API ....................................................................... 34

1.12 Blocking and Non blocking embOS API ..........................................................35

1.13 API functions ............................................................................................. 36

2 Tasks ........................................................................................................................... 42

2.1 Introduction .................................................................................................43

2.2 Cooperative vs. preemptive task switches ....................................................... 44

2.3 Extending the task context ............................................................................45

2.4 API functions ............................................................................................... 47

3 Software Timers ..........................................................................................................90

3.1 Introduction .................................................................................................91

3.2 API functions ............................................................................................... 93

4 Task Events ...............................................................................................................119

4.1 Introduction ............................................................................................... 120

4.2 API functions ............................................................................................. 121

5 Event Objects ............................................................................................................130

5.1 Introduction ............................................................................................... 131

5.2 API functions ............................................................................................. 134

6 Mutexes .....................................................................................................................154

6.1 Introduction ............................................................................................... 155

6.2 API functions ............................................................................................. 157

7 Semaphores .............................................................................................................. 167

7.1 Introduction ............................................................................................... 168

7.2 API functions ............................................................................................. 169

8 Mailboxes .................................................................................................................. 180

8.1 Introduction ............................................................................................... 181

8.2 API functions ............................................................................................. 184

9 Queues ......................................................................................................................212

9.1 Introduction ............................................................................................... 213

9.2 API functions ............................................................................................. 215

10 Watchdog ................................................................................................................ 234

10.1 Introduction ............................................................................................. 235

10.2 API functions ........................................................................................... 236

11 Multi-core Support .................................................................................................. 242

11.1 Introduction ............................................................................................. 243

11.2 API functions ........................................................................................... 245

12 Interrupts ................................................................................................................. 252

12.1 What are interrupts? ................................................................................. 253

12.2 Interrupt latency ...................................................................................... 254

12.3 Rules for interrupt handlers ....................................................................... 258

12.4 Interrupt control .......................................................................................268

13 Critical Regions .......................................................................................................279

13.1 Introduction ............................................................................................. 280

13.2 API functions ........................................................................................... 281

14 Time Measurement ................................................................................................. 284

14.1 Introduction ............................................................................................. 285

14.2 Low-resolution measurement ..................................................................... 286

14.3 High-resolution measurement .....................................................................289

14.4 Example .................................................................................................. 295

14.5 Microsecond precise system time ................................................................296

15 Low Power Support ................................................................................................ 301

15.1 Introduction ............................................................................................. 302

15.2 Starting power save modes in OS_Idle() ..................................................... 303

15.3 Tickless support ....................................................................................... 304

15.4 Peripheral power control ............................................................................ 312

16 Heap Type Memory Management .......................................................................... 317

16.1 Introduction ............................................................................................. 318

16.2 API functions ........................................................................................... 319

17 Fixed Block Size Memory Pool ...............................................................................323

17.1 Introduction ............................................................................................. 324

17.2 API functions ........................................................................................... 326

18 System Tick ............................................................................................................ 339

18.1 Introduction ............................................................................................. 340

18.2 API functions ........................................................................................... 340

18.3 Hooking into the system tick ..................................................................... 345

18.5 Disabling the system tick .......................................................................... 348

19 Debugging ............................................................................................................... 349

19.1 Runtime application errors ......................................................................... 350

19.2 Human readable object identifiers ...............................................................356

20 Profiling ................................................................................................................... 359

20.1 Introduction ............................................................................................. 360

20.2 API functions ........................................................................................... 361

21 embOSView ............................................................................................................ 371

21.1 Overview ................................................................................................. 372

21.2 Task list window ....................................................................................... 373

21.3 System variables window ...........................................................................374

21.4 Sharing the SIO for terminal I/O ................................................................ 375

21.5 Enable communication to embOSView ......................................................... 378

21.6 Select the communication channel .............................................................. 379

21.7 Setup embOSView for communication ......................................................... 380

21.8 Using the API trace .................................................................................. 384

21.9 Trace filter setup functions .........................................................................386

21.10 Trace record functions ............................................................................. 395

21.11 Application-controlled trace example ......................................................... 401

21.12 User-defined functions ............................................................................. 402

22 MPU - Memory Protection ...................................................................................... 403

22.1 Introduction ............................................................................................. 404

22.2 Memory Access permissions ....................................................................... 405

22.3 ROM placement of embOS ......................................................................... 406

22.4 Allowed embOS API in unprivileged tasks .................................................... 407

22.5 Device driver ........................................................................................... 412

22.6 API functions ........................................................................................... 414

23 Stacks ......................................................................................................................430

23.1 Introduction ............................................................................................. 431

23.2 API functions ........................................................................................... 433

24 Board Support Packages ........................................................................................448

24.1 Introduction ............................................................................................. 449

24.2 Hardware-specific routines ......................................................................... 450

24.3 How to change settings .............................................................................461

25 System Variables .................................................................................................... 462

25.1 Introduction ............................................................................................. 463

25.2 Time variables ..........................................................................................464

25.3 OS information routines ............................................................................ 465

26 Supported Development Tools ................................................................................471

26.1 Overview ................................................................................................. 472

27 Source Code ........................................................................................................... 473

27.1 Introduction ............................................................................................. 474

27.2 Building embOS libraries ........................................................................... 475

27.3 Compile time switches .............................................................................. 476

27.4 Source code project .................................................................................. 478

28 Shipment ................................................................................................................. 479

28.1 General information .................................................................................. 480

28.2 Library variant ..........................................................................................481

28.3 Free variant ............................................................................................. 482

28.4 Source code variant .................................................................................. 483

29 Update .....................................................................................................................484

29.1 Introduction ............................................................................................. 485

29.2 How to update an existing project .............................................................. 486

29.3 embOS API Migration guide ....................................................................... 487

30 Support ....................................................................................................................495

30.1 Contacting support ................................................................................... 496

31 Performance and Resource Usage .........................................................................497

31.1 Introduction ............................................................................................. 498

31.2 Memory requirements ............................................................................... 499

31.3 Performance .............................................................................................500

31.4 Benchmarking .......................................................................................... 500

32 Glossary .................................................................................................................. 505

Chapter 1

Introduction and basic

concepts

18 CHAPTER 1 What is embOS?

1.1 What is embOS?

embOS is a priority-controlled multitasking system, designed to be used as an embedded

operating system for the development of real-time applications for a variety of microcon-

trollers.

embOS is a high-performance tool that has been optimized for minimal memory consump-

tion in both RAM and ROM, as well as high speed and versatility.

Throughout the development process of embOS, the limited resources of microcontrollers

have always been kept in mind. The internal structure of the real-time operating system

(RTOS) has been optimized in a variety of applications with different customers, to fit the

needs of industry. Fully source-compatible implementations of embOS are available for a

variety of microcontrollers, making it well worth the time and effort to learn how to structure

real-time programs with real-time operating systems.

embOS is highly modular. This means that only those functions that are required are linked

into an application, keeping the ROM size very small. The minimum memory consumption

is little more than 1.7 Kbyte of ROM and about 70 bytes of RAM (plus memory for stacks). A

couple of files are supplied in source code to make sure that you do not loose any flexibility

by using embOS libraries and that you can customize the system to fully fit your needs.

The tasks you create can easily and safely communicate with each other using a number

of communication mechanisms such as semaphores, mailboxes, and events.

Some features of embOS include:

• Preemptive scheduling:

Guarantees that of all tasks in READY state the one with the highest priority executes,

except for situations in which priority inheritance applies.

• Round-robin scheduling for tasks with identical priorities.

• Preemptions can be disabled for entire tasks or for sections of a program.

• Up to 4,294,967,296 priorities.

• Every task can have an individual priority, which means that the response of tasks can

be precisely defined according to the requirements of the application.

• Unlimited number of tasks

(limited only by the amount of available memory).

• Unlimited number of semaphores

(limited only by the amount of available memory).

• Two types of semaphores: Mutex and counting semaphores.

• Unlimited number of mailboxes

(limited only by the amount of available memory).

• Size and number of messages can be freely defined when initializing mailboxes.

• Unlimited number of software timers

(limited only by the amount of available memory).

• Up to 32 bit events for every task.

• Time resolution can be freely selected (default is 1 msec).

• Easily accessible time variable.

• Power management.

• Calculation time in which embOS is idle can automatically be spent in power save mode.

Power-consumption is minimized.

• Full interrupt support:

Interrupts may call any function except those that require waiting for data, as well

as create, delete or change the priority of a task. Interrupts can wake up or suspend

tasks and directly communicate with tasks using all available communication methods

(mailboxes, semaphores, events).

• Disabling interrupts for very short periods allows minimal interrupt latency.

• Nested interrupts are permitted.

• embOS has its own, optional interrupt stack.

• Application samples for an easy start.

• Debug build performs runtime checks that catch common programming errors early on.

• Profiling and stack-check may be implemented by choosing specified libraries.

• Monitoring during runtime is available using embOSView via UART, Debug

Communications Channel (DCC) and memory read/write, or else via Ethernet.

19 CHAPTER 1 What is embOS?

• Very fast and efficient, yet small code.

• Minimal RAM usage.

• API can be called from assembly, C or C++ code.

• Board support packages (BSP) as source code available.

20 CHAPTER 1 Tasks

1.2 Tasks

In this context, a task is a program running on the CPU core of a microcontroller. Without

a multitasking kernel (an RTOS), only one task can be executed by the CPU. This is called a

single-task system. A real-time operating system, on the other hand, allows the execution

of multiple tasks on a single CPU. All tasks execute as if they completely “owned” the

entire CPU. The tasks are scheduled for execution, meaning that the RTOS can activate and

deactivate each task according to its priority, with the highest priority task being executed

in general.

1.2.1 Threads vs. Processes

Threads are tasks that share the same memory layout, hence any two threads can access

the same memory locations. If virtual memory is used, the same virtual to physical trans-

lation and access rights are used.

With embOS, all tasks are threads: they all have the same memory access rights and

translation (in systems with virtual memory).

Processes are tasks with their own memory layout. Two processes cannot normally access

the same memory locations. Different processes typically have different access rights and

(in case of MMUs) different translation tables. Processes are not supported with the current

version of embOS.

21 CHAPTER 1 Single-task systems (superloop)

1.3 Single-task systems (superloop)

The classic way of designing embedded systems does not use the services of an RTOS,

which is also called “superloop design”. Typically, no real time kernel is used, so interrupt

service routines (ISRs) are used for the real-time parts of the application and for critical

operations (at interrupt level). This type of system is typically used in small, simple systems

or if real-time behavior is not critical.

Typically, since no real-time kernel and only one stack is used, both program (ROM) size and

RAM size are smaller for simple applications when compared to using an RTOS. Obviously,

there are no inter-task synchronization problems with a superloop application. However,

superloops can become difficult to maintain if the program becomes too large or uses

complex interactions. As sequential processes cannot interrupt themselves, reaction times

depend on the execution time of the entire sequence, resulting in a poor real-time behavior.

1.3.1 Advantages & disadvantages

Advantages

• Simple structure (for small applications)

• Low stack usage (only one stack required)

Disadvantages

• No “delay” capability

• Higher power consumption due to the lack of a power save mode in most architectures

• Difficult to maintain as program grows

• Timing of all software components depends on all other software components:

Small change in one place can have major side effects in other places

• Defeats modular programming

• Real time behavior only with interrupts

1.3.2 Using embOS in superloop applications

In a true superloop application, no tasks are used, hence the biggest advantage of using

an RTOS cannot be utilized unless the application is re-written for multitasking. However,

even with just one single task, using embOS offers the following advantages:

• Software timers are available

• Power saving: Idle mode can be used

• Future extensions can be put in a separate task

1.3.3 Migrating from superloop to multi-tasking

A common situation is that an application exists for some time and has been designed as

a single-task super-loop-application. At some point, the disadvantages of this approach

result in a decision to use an RTOS. The typical question now usually is: How do I do this?

The easiest way is to start with one of the sample applications that come with embOS and

to add the existing “super-loop code” into one task. At this point, you should also ensure

that the stack size of this task is sufficient. Later, additional functionality is added to the

22 CHAPTER 1 Single-task systems (superloop)

software and can be put in one or more additional tasks; the functionality of the super-loop

can also be distributed over multiple tasks.

23 CHAPTER 1 Multitasking systems

1.4 Multitasking systems

In a multitasking system, there are different ways to distribute CPU time amongst different

tasks. This process is called scheduling.

1.4.1 Task switches

There are two types of task switches, also called context switches: Cooperative and pre-

emptive task switches.

A cooperative task switch is performed by the task itself. As its name indicates, it requires

the cooperation of the task: it suspends itself by calling a blocking RTOS function, e.g.

OS_TASK_Delay() or OS_TASKEVENT_GetBlocked().

A preemptive task switch, on the other hand, is a task switch that is caused externally.

For example, a task of higher priority becomes ready for execution and, as a result, the

scheduler suspends the current task in favor of that task.

1.4.2 Cooperative multitasking

Cooperative multitasking requires all tasks to cooperate by using blocking functions. A task

switch can only take place if the running task blocks itself by calling a blocking function

such as OS_TASK_Delay() or OS_MAILBOX_GetBlocked(). If tasks do not cooperate, the

system “hangs”, which means that other tasks have no chance of being executed by the

CPU while the first task is being carried out. This is illustrated in the diagram below. Even

if an ISR makes a higher-priority task ready to run, the interrupted task will be resumed

and complete before the task switch is made.

A pure cooperative multi-tasking system has the disadvantage of longer reaction times

when high priority tasks become ready for execution. This makes their usage in embedded

real-time systems uncommon.

24 CHAPTER 1 Multitasking systems

1.4.3 Preemptive multitasking

Real-time operating systems like embOS operate with preemptive multitasking. The high-

est-priority task in the READY state always executes as long as the task is not suspended by

a call of any blocking operating system function. A high-priority task waiting for an event is

signaled READY as soon as the event occurs. The event can be set by an interrupt handler,

which then activates the task immediately. Other tasks with lower priority are suspended

(preempted) for as long as the high-priority task is executing. Usually, real-time operating

systems such as embOS utilize a timer interrupt that interrupts tasks at periodic intervals

and thereby allows to perform task switches whenever timed task switches are necessary.

Preemptive multitasking may be switched off in sections of a program where task switch-

es are prohibited, known as critical regions. embOS itself will also temporarily disable pre-

emptive task switches during critical operations, which might be performed during the ex-

ecution of some embOS API functions.

25 CHAPTER 1 Scheduling

1.5 Scheduling

There are different algorithms that determine which task to execute, called schedulers. All

schedulers have one thing in common: they distinguish between tasks that are ready to be

executed (in the READY state) and other tasks that are suspended for some reason (delay,

waiting for mailbox, waiting for semaphore, waiting for event, etc). The scheduler selects

one of the tasks in the READY state and activates it (executes the body of this task). The task

which is currently executing is referred to as the running task. The main difference between

schedulers is the way they distribute computation time between tasks in the READY state.

1.5.1 Round-robin scheduling algorithm

With round-robin scheduling, the scheduler has a list of tasks and, when deactivating the

running task, activates the next task that is in the READY state. Round-robin can be used

with either preemptive or cooperative multitasking. It works well if you do not need to

guarantee response time. Round-robin scheduling can be illustrated as follows:

All tasks share the same priority; the possession of the CPU changes periodically after a

predefined execution time. This time is called a time slice and may be defined individually

for each task.

1.5.2 Priority-controlled scheduling algorithm

In real-world applications, different tasks require different response times. For example, in

an application that controls a motor, a keyboard, and a display, the motor usually requires

faster reaction time than the keyboard and the display. E.g., even while the display is being

updated, the motor needs to be controlled. This renders preemptive multitasking essential.

Round-robin might work, but as it cannot guarantee any specific reaction time, a more

suitable algorithm should be used.

In priority-controlled scheduling, every task is assigned a priority. Depending on these

priorities, a task is chosen for execution according to one simple rule:

Note

The scheduler activates the task that has the highest priority of all tasks and is ready

for execution.

This means that every time a task with a priority higher than the running task becomes

ready, it becomes the running task, and the previous task gets preempted. However, the

scheduler can be switched off in sections of a program where task switches are prohibited,

known as critical regions.

embOS uses a priority-controlled scheduling algorithm with round-robin between tasks of

identical priority. One hint at this point: round-robin scheduling is a nice feature because

you do not need to decide whether one task is more important than another. Tasks with

identical priority cannot block each other for longer periods than their time slices. But

round-robin scheduling also costs time if two or more tasks of identical priority are ready

and no task of higher priority is, because execution constantly switches between the identi-

cal-priority tasks. It usually is more efficient to assign distinct priority to each task, thereby

avoiding unnecessary task switches.

26 CHAPTER 1 Scheduling

1.5.3 Priority inversion / priority inheritance

The rule the scheduler obeys is:

Activate the task that has the highest priority of all tasks in the READY state.

But what happens if the highest-priority task is blocked because it is waiting for a resource

owned by a lower-priority task? According to the above rule, it would wait until the low-

priority task is resumed and releases the resource. Up to this point, everything works as

expected. Problems arise when a task with medium priority becomes ready during the

execution of the higher prioritized task.

When the higher priority task is suspended waiting for the resource, the task with the

medium priority will run until it finishes its work, because it has a higher priority than the

low-priority task. In this scenario, a task with medium priority runs in place of the task with

high priority. This is known as priority inversion.

The low priority task claims the semaphore with OS_MUTEX_LockBlocked(). An interrupt

activates the high priority task, which also calls OS_MUTEX_LockBlocked(). Meanwhile a

task with medium priority becomes ready and runs when the high priority task is suspend-

ed. The task with medium priority eventually calls OS_TASK_Delay() and is therefore sus-

pended. The task with lower priority now continues and calls OS_MUTEX_Unlock() to release

the mutex. After the low priority task releases the semaphore, the high priority task is

activated and claims the semaphore.

To avoid this situation, embOS temporarily raises the low-priority task to high priority until

it releases the resource. This unblocks the task that originally had the highest priority and

can now be resumed. This is known as priority inheritance.

With priority inheritance, the low priority task inherits the priority of the waiting high priority

task as long as it holds the mutex. The lower priority task is activated instead of the medium

priority task when the high priority task tries to claim the semaphore.

27 CHAPTER 1 Communication between tasks

1.6 Communication between tasks

In a multitasking (multithreaded) program, multiple tasks and ISRs work completely sep-

arately. Because they all work in the same application, it will sometimes be necessary for

them to exchange information with each other.

1.6.1 Periodic polling

The easiest way to communicate between different pieces of code is by using global vari-

ables. In certain situations, it can make sense for tasks to communicate via global variables,

but most of the time this method has disadvantages.

For example, if you want to synchronize a task to start when the value of a global variable

changes, you must continually poll this variable, wasting precious computation time and

energy, and the reaction time depends on how often you poll.

1.6.2 Event-driven communication mechanisms

When multiple tasks work with each other, they often have to:

• exchange data,

• synchronize with another task, or

• make sure that a resource is used by no more than one task at a time.

For these purposes embOS offers mailboxes, queues, semaphores and events.

1.6.3 Mailboxes and queues

A mailbox is a data buffer managed by the RTOS and is used for sending a message to

a task. It works without conflicts even if multiple tasks and interrupts try to access the

same mailbox simultaneously. embOS activates any task that is waiting for a message in

a mailbox the moment it receives new data and, if necessary, switches to this task.

A queue works in a similar manner, but handles larger messages than mailboxes, and each

message may have an individual size.

For more information, refer to the chapters Mailboxes on page 180 and Queues on

page 212.

1.6.4 Semaphores and Mutexes

Semaphores and mutexes are used for task synchronization and to manage resources of

any kind. The most common are mutex, although semaphores are also used.

For details and samples, refer to the chapters Mutexes on page 154 and Semaphores on

page 167.

1.6.5 Events

A task can wait for a particular event without consuming any CPU time. The idea is as

simple as it is convincing, there is no sense in polling if we can simply activate a task once

the event it is waiting for occurs. This saves processor cycles and energy and ensures that

the task can respond to the event without delay. Typical applications for events are those

where a task waits for some data, a pressed key, a received command or character, or the

pulse of an external real-time clock.

For further details, refer to the chapters Task Events on page 119 and Event Objects on

page 130.

28 CHAPTER 1 How task switching works

1.7 How task switching works

A real-time multitasking system lets multiple tasks run like multiple single-task programs,

quasi-simultaneously, on a single CPU. A task consists of three parts in the multitasking

world:

• The program code, which typically resides in ROM

• A stack, residing in a RAM area that can be accessed by the stack pointer

• A task control block, residing in RAM.

The task’s stack has the same function as in a single-task system: storage of return ad-

dresses of function calls, parameters and local variables, and temporary storage of inter-

mediate results and register values. Each task can have a different stack size. More infor-

mation can be found in chapter Stacks on page 430.

The task control block (TCB) is a data structure assigned to a task when it is created.

The TCB contains status information for the task, including the stack pointer, task priority,

current task status (ready, waiting, reason for suspension) and other management data.

Knowledge of the stack pointer allows access to the other registers, which are typically

stored (pushed onto) the stack when the task is created and each time it is suspended.

This information allows an interrupted task to continue execution exactly where it left off.

TCBs are only accessed by the RTOS.

29 CHAPTER 1 How task switching works

1.7.1 Switching stacks

The following diagram demonstrates the process of switching from one stack to another.

The scheduler deactivates the task to be suspended (Task 0) by saving the processor reg-

isters on its stack. It then activates the higher-priority task (Task 1) by loading the stack

pointer (SP) and the processor registers from the values stored on Task 1’s stack.

Deactivating a task

The scheduler deactivates the task to be suspended (Task 0) as follows:

1. Save (push) the processor registers on the task’s stack.

2. Save the stack pointer in the Task Control Block.

Activating a task

The scheduler activates the higher-priority task (Task 1) by performing the sequence in

reverse order:

1. Load (pop) the stack pointer (SP) from the Task Control Block.

2. Load the processor registers from the values stored on Task 1’s stack.

30 CHAPTER 1 Change of task status

1.8 Change of task status

A task may be in one of several states at any given time. When a task is created, it is

placed into the READY state.

A task in the READY state is activated as soon as there is no other task in the READY state

with higher priority. Only one task may be running at a time. If a task with higher priority

becomes READY, this higher priority task is activated and the preempted task remains in

the READY state.

The running task may be delayed for or until a specified time; in this case it is placed into

the WAITING state and the next-highest-priority task in the READY state is activated.

The running task might need to wait for an event (or semaphore, mailbox or queue). If

the event has not yet occurred, the task is placed into the waiting state and the next-

highest-priority task in the READY state is activated.

A non-existent task is one that is not yet available to embOS; it either has been terminated

or was not created at all.

The following illustration shows all possible task states and transitions between them.

31 CHAPTER 1 How the OS gains control

1.9 How the OS gains control

Upon CPU reset, the special-function registers are set to their default values. After reset,

program execution begins: The PC register is set to the start address defined by the start

vector or start address (depending on the CPU). This start address is usually in a startup

module shipped with the C compiler, and is sometimes part of the standard library.

The startup code performs the following:

• Loads the stack pointer(s) with the default values, which is for most CPUs the end of

the defined stack segment(s)

• Initializes all data segments to their respective values

• Calls the main() function.

The main() function is the part of your program which takes control immediately after

the C startup. Normally, embOS works with the standard C startup module without any

modification. If there are any changes required, they are documented in the CPU & Compiler

Specifics manual of the embOS documentation.

With embOS, the main() function is still part of your application program. Essentially,

main() creates one or more tasks and then starts multitasking by calling OS_Start(). From

this point, the scheduler controls which task is executed.

Startup_code()

main()

OS_Init();

OS_InitHW();

OS_TASK_CREATE();

OS_Start();

The main() function will not be interrupted by any of the created tasks because those

tasks execute only following the call to OS_Start(). It is therefore usually recommended to

create all or most of your tasks here, as well as your control structures such as mailboxes

and semaphores. Good practice is to write software in the form of modules which are (up

to a point) reusable. These modules usually have an initialization routine, which creates

any required task(s) and control structures. A typical main() function looks similar to the

following example:

Example

void main(void) {

OS_Init(); // Initialize embOS (must be first)

OS_InitHW(); // Initialize hardware for embOS (in RTOSInit.c)

// Call Init routines of all program modules which in turn will create

// the tasks they need ... (Order of creation may be important)

MODULE1_Init();

MODULE2_Init();

MODULE3_Init();

MODULE4_Init();

MODULE5_Init();

OS_Start(); // Start multitasking

}

With the call to OS_Start(), the scheduler starts the highest-priority task created in

main(). Note that OS_Start() is called only once during the startup process and does not

return.

32 CHAPTER 1 Different builds of embOS

1.10 Different builds of embOS

embOS comes in different builds or versions of the libraries. The reason for different builds

is that requirements vary during development. While developing software, the performance

(and resource usage) is not as important as in the final version which usually goes as

release build into the product. But during development, even small programming errors

should be caught by use of assertions. These assertions are compiled into the debug build

of the embOS libraries and make the code a little bigger (about 50%) and also slightly

slower than the release or stack-check build used for the final product.

This concept gives you the best of both worlds: a compact and very efficient build for your

final product (release or stack-check build of the libraries), and a safer (though bigger

and slower) build for development which will catch most common application programming

errors. Of course, you may also use the release build of embOS during development, but

it will not catch these errors.

The following features are included in the different embOS builds:

Debug code

The embOS debug code is mainly implemented as assertions which detect application pro-

gramming errors like calling an API function from an invalid context.

Stack check

The stack check detects stack overflows of task stacks, system stack and interrupt stack.

Also the maximum amount of used stack can be calculated.

Profiling

embOS supports profiling in profiling builds. Profiling makes precise information available

about the execution time of individual tasks. You may always use the profiling libraries, but

they require larger task control blocks, additional ROM and additional runtime overhead.

This overhead is usually acceptable, but for best performance you may want to use non-

profiling builds of embOS if you do not use this feature.

Trace

embOS API trace saves information about called API in a trace buffer. The trace data can

be visualized in embOSView.

Round-Robin

Round-Robin lets all task at the same priority periodically run with an according time slice.

Object names

Tasks and OS object names can be used to easily identify a task or e.g. a mailbox in tools

like embOSView, SystemView or IDE RTOS plug-ins.

Task context extension

For some applications it might be useful or required to have individual data in tasks that are

unique to the task. With the task context extension support each task control block includes

function pointer to save and restore routines which are executed during context switch.

33 CHAPTER 1 Different builds of embOS

1.10.1 List of builds

In your application program, you need to let the compiler know which build of embOS you

are using. This is done by adding the corresponding Define to your preprocessor settings

and linking the according library file. The actual library file name depends on the embOS

port. Please check the according CPU and compiler specific embOS manual for more details.

Name Define

Debug Code

Stack Check

Profiling

Trace

Round-Robin

Object names

Task context

extension

Description

Extreme

Release OS_LIBMODE_XR Smallest fastest build.

Release OS_LIBMODE_R ● ● ●

Small, fast build, normally

used for release build of ap-

plication.

Stack Check OS_LIBMODE_S ● ● ● ● Same as release, plus stack

checking.

Stackcheck

+ Profiling OS_LIBMODE_SP ● ● ● ● ● Same as stack check, plus

profiling.

Debug OS_LIBMODE_D ● ● ● ● ● Maximum runtime checking.

Debug +

Profiling OS_LIBMODE_DP ● ● ● ● ● ● Maximum runtime checking,

plus profiling.

Debug +

Trace +

Profiling

OS_LIBMODE_DT ●●●●●● ●

Maximum runtime checking,

plus tracing API callss and

profiling.

Safe Library OS_LIBMODE_SAFE ● ● ● ● ● ● Additional safety features

for certified embOS.

1.10.2 OS_Config.h

OS_Config.h is part of every embOS port and located in the Start\Inc folder. Use of

OS_Config.h makes it easier to define the embOS library mode: Instead of defining OS_LIB-

MODE_* in your preprocessor settings, you may define DEBUG=1 in your preprocessor settings

in debug compile configuration and define nothing in the preprocessor settings in release

compile configuration. Subsequently, OS_Config.h will automatically define OS_LIBMOD-

E_DP for debug compile configuration and OS_LIBMODE_R for release compile configuration.

Compile Configuration Preprocessor Define Define Set by OS_Config.h

Debug DEBUG=1 OS_LIBMODE_DP

Release OS_LIBMODE_R

34 CHAPTER 1 Valid context for embOS API

1.11 Valid context for embOS API

Some embOS functions may only be called from specific locations inside your application.

We distinguish between main() (before the call of OS_Start()), task, interrupt routines

and embOS software timer.

Note

Please consult the embOS API tables to determine whether an embOS function is

allowed from within a specific execution context. Please find the API tables at beginning

of each chapter.

An embOS debug build will check for violations of these rules and calls OS_Error() with

an according error code.

Example

Routine Description

main

Task

ISR

Timer

OS_TASK_Delay() Suspends the calling task for a specified period of

time, or waits actively when called from main(). ● ●

This table entry says it is allowed to call OS_TASK_Delay() from main() and a task but not

from an embOS software timer or an interrupt handler.

35 CHAPTER 1 Blocking and Non blocking embOS API

1.12 Blocking and Non blocking embOS API

Most embOS API comes in three different version: Non blocking, blocking and blocking with

a timeout. The embOS API uses a specific naming convention for those API functions. API

functions which do not block a task have no suffix. API functions which could block a task

have the suffix “Blocked”. API functions which could block a task but have a timeout have

the suffix “Timed”.

Non blocking API

Non blocking API functions always return at once, irrespective of the state of the OS object.

The return value can be checked in order to find out if e.g. new data is available in a mailbox.

static OS_MAILBOX MyMailbox;

static char Buffer[10];

void Task(void) {

char r;

while (1) {

r = OS_MAILBOX_Get(MyMailbox, Buffer);

if (r == 0u) {

// Process message

}

Blocking API

Blocking API functions suspend the task until it is activated again by another embOS API

function. The task does not cause any CPU load while it is waiting for the next activation.

static OS_MAILBOX MyMailbox;

static char Buffer[10];

void Task(void) {

while (1) {

// Suspend task until a new message is available

OS_MAILBOX_GetBlocked(MyMailbox, Buffer);

// Process message

}

Blocking API with timeout

These API functions have an additional timeout. They are blocking until the timeout occurs.

static OS_MAILBOX MyMailbox;

static char Buffer[10];

void Task(void) {

char r;

while (1) {

// Suspend task until a new message is available or the timeout occurs

r = OS_MAILBOX_GetTimed(MyMailbox, Buffer, 10);

if (r == 0u) {

// Process message

}

36 CHAPTER 1 API functions

1.13 API functions

Routine Description

main

Task

ISR

Timer

OS_ConfigStop() Configures the OS_Stop() function. ●

OS_Init() Initializes the embOS kernel. ●

OS_IsRunning() Returns whether OS_Start() was called. ● ● ● ●

OS_Start() Starts the embOS kernel. ●

OS_Stop() Stops the embOS scheduler and returns from OS_S-

tart().●●●●

37 CHAPTER 1 API functions

1.13.1 OS_ConfigStop()

Description

Configures the OS_Stop() function.

Prototype

void OS_ConfigStop(OS_MAIN_CONTEXT* pContext,

void* Addr,

OS_U32 Size);

Parameters

Parameter Description

pContext Pointer to an object of type OS_MAIN_CONTEXT.

Addr Address of the buffer which is used to save the main() stack.

Size Size of the buffer.

Additional information

This function configures the OS_Stop() function. When configured, OS_Start() saves the

context and stack from within main(), which subsequently are restored by OS_Stop(). The

main() context and stack are saved to the resources configured by OS_ConfigStop(). Only

the stack that was actually used during main() is saved. Therefore, the size of the buffer

depends on the used stack. If the buffer is too small, debug builds of embOS will call

OS_Error() with the error code OS_ERR_OSSTOP_BUFFER. The structure OS_MAIN_CONTEXT

is core and compiler specific; it is specifically defined with each embOS port.

Example

#include "RTOS.h"

#include "stdio.h"

#define BUFFER_SIZE (32u)

static OS_U8 Buffer[BUFFER_SIZE]; // Buffer for main stack copy

static OS_MAIN_CONTEXT MainContext; // Main context control structure

static OS_STACKPTR int StackHP[128]; // Task stack

static OS_TASK TCBHP; // Task control block

static void HPTask(void) {

OS_TASK_Delay(50);

OS_INT_Disable();

OS_Stop();

}

int main(void) {

int TheAnswerToEverything = 42;

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_ConfigStop(&MainContext, Buffer, BUFFER_SIZE);

OS_Start(); // Start embOS

// We arrive here because OS_Stop() was called.

// The local stack variable still has its value.

printf("%d", TheAnswerToEverything);

while (TheAnswerToEverything == 42) {

}

return 0;

}

38 CHAPTER 1 API functions

1.13.2 OS_Init()

Description

Initializes the embOS kernel.

Prototype

void OS_Init(void);

Additional information

In library mode OS_LIBMODE_SAFE all RTOS variables are explicitly initialized. All other li-

brary modes presume that, according to the C standard, all initialized variables have their

initial value and all non initialized variables are set to zero.

Note

OS_Init() must be called in main() prior to any other embOS API.

Example

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void HPTask(void) {

while (1) {

OS_TASK_Delay(50);

}

static void LPTask(void) {

while (1) {

OS_TASK_Delay(200);

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

39 CHAPTER 1 API functions

1.13.3 OS_IsRunning()

Description

Determines whether the embOS scheduler was started by a call of OS_Start().

Prototype

OS_BOOL OS_IsRunning(void);

Return value

= 0 Scheduler is not started.

≠ 0 Scheduler is running, OS_Start() has been called.

Additional information

This function may be helpful for some functions which might be called from main() or from

running tasks. As long as the scheduler is not started and a function is called from main(),

blocking task switches are not allowed. A function which may be called from a task or

main() may use OS_IsRunning() to determine whether a subsequent call to a blocking API

function is allowed.

Example

void PrintStatus() {

OS_BOOL b;

b = OS_ISRunning();

if (b == 0) {

printf("embOS scheduler not started, yet.\n");

} else {

printf("embOS scheduler is running.\n");

}

40 CHAPTER 1 API functions

1.13.4 OS_Start()

Description

Starts the embOS scheduler.

Prototype

void OS_Start(void);

Additional information

This function starts the embOS scheduler, which will activate and start the task with the

highest priority.

OS_Start() marks embOS as running; this may be examined by a call of the function

OS_IsRunning(). OS_Start() automatically enables interrupts. It must be called from

main() only.

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void HPTask(void) {

while (1) {

OS_TASK_Delay(50);

}

static void LPTask(void) {

while (1) {

OS_TASK_Delay(200);

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

41 CHAPTER 1 API functions

1.13.5 OS_Stop()

Description

Stops the embOS scheduler and returns from OS_Start().

Prototype

void OS_Stop(void);

Additional information

This function stops the embOS scheduler and the application returns from OS_Start().

OS_ConfigStop() must be called prior to OS_Stop(). If OS_ConfigStop() was not called,

debug builds of embOS will call OS_Error() with the error code OS_ERR_CONFIG_OSSTOP.

OS_Stop() restores context and stack to their state prior to calling OS_Start(). OS_Stop()

does not deinitialize any hardware. It’s the application’s responsibility to deinitialize all

hardware that was initialzed during OS_InitHW().

It is possible to restart embOS after OS_Stop(). To do so, OS_Init() must be called and

any task must be recreated. It also is the application’s responsibility to initialize all embOS

variables to their default values. With the embOS source code, this can easily be achived

using the compile time switch OS_INIT_EXPLICITLY.

With some cores it is not possible to save and restore the main() stack. This is e.g. true for

8051. Hence, in that case no functionality should be implemented that relies on the stack

to be preserved. But OS_Stop() can be used anyway.

Example

#include "RTOS.h"

#include "stdio.h"

#define BUFFER_SIZE (32u)

static OS_U8 Buffer[BUFFER_SIZE];

static OS_MAIN_CONTEXT MainContext;

static OS_STACKPTR int StackHP[128];

static OS_TASK TCBHP;

static void HPTask(void) {

OS_TASK_Delay(50);

OS_Stop();

}

int main(void) {

int TheAnswerToEverything = 42;

OS_Init();

OS_InitHW();

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_ConfigStop(&MainContext, Buffer, BUFFER_SIZE);

OS_Start();

// We arrive here because OS_Stop() was called.

// The local stack variable still has its value.

printf("%d", TheAnswerToEverything);

while (1) {

}

return 0;

}

Chapter 2

Tasks

43 CHAPTER 2 Introduction

2.1 Introduction

A task that should run under embOS needs a task control block (TCB), a task stack, and a

task body written in C. The following rules apply to task routines:

• The task routine can either not take parameters (void parameter list), in which case

OS_TASK_Create() is used to create it, or take a single void pointer as parameter, in

which case OS_TASK_CreateEx() is used to create it.

• The task routine must not return.

• The task routine must be implemented as an endless loop or it must terminate itself

(see examples below).

2.1.1 Example of a task routine as an endless loop

void Task1(void) {

while(1) {

DoSomething(); // Do something

OS_TASK_Delay(10); // Give other tasks a chance to run

}

2.1.2 Example of a task routine that terminates itself

void Task2(void) {

char DoSomeMore;

do {

DoSomeMore = DoSomethingElse(); // Do something

OS_TASK_Delay(10); // Give other tasks a chance to run

} while (DoSomeMore);

OS_TASK_Terminate(NULL); // Terminate yourself

}

There are different ways to create a task: On the one hand, embOS offers a simple macro

to facilitate task creation which is sufficient in most cases. However, if you are dynamically

creating and deleting tasks, a function is available allowing “fine-tuning” of all parameters.

For most applications, at least initially, we recommend using the macro as in the sample

start projects.

44 CHAPTER 2 Cooperative vs. preemptive task switches

2.2 Cooperative vs. preemptive task switches

In general, preemptive task switches are an important feature of an RTOS. Preemptive

task switches are required to guarantee responsiveness of high-priority, time critical tasks.

However, it may be desirable to disable preemptive task switches for certain tasks in some

circumstances. The default behavior of embOS is to always allow preemptive task switches.

2.2.1 Disabling preemptive task switches for tasks of equal

priority

In some situations, preemptive task switches between tasks running at identical priorities

are not desirable. To inhibit time slicing of equal-priority tasks, the time slice of the tasks

running at identical priorities must be set to zero as in the example below:

#include "RTOS.h"

#define PRIO_COOP 10

#define TIME_SLICE_NULL 0

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void TaskEx(void* pData) {

while (1) {

OS_TASK_Delay ((OS_TIME) pData);

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

BSP_Init(); // Initialize LED ports

OS_TASK_CreateEx(&TCBHP, "HP Task", PRIO_COOP, TaskEx, StackHP,

sizeof(StackHP), TIME_SLICE_NULL, (void *) 50);

OS_TASK_CreateEx(&TCBLP, "LP Task", PRIO_COOP, TaskEx, StackLP,

sizeof(StackLP), TIME_SLICE_NULL, (void *) 200);

OS_Start(); // Start embOS

return 0;

}

2.2.2 Completely disabling preemptions for a task

This is simple: The first line of code should be OS_TASK_EnterRegion() as shown in the

following sample:

void MyTask(void* pContext) {

OS_TASK_EnterRegion(); // Disable preemptive context switches

while (1) {

// Do something. In the code, make sure that you call a blocking

// funtion periodically to give other tasks a chance to run.

}

This will entirely disable preemptive context switches from that particular task and will

therefore affect the timing of higher-priority tasks. Do not use this carelessly.

45 CHAPTER 2 Extending the task context

2.3 Extending the task context

For some applications it might be useful or required to have individual data in tasks that are

unique to the task. Local variables, declared in the task, are unique to the task and remain

valid, even when the task is suspended and resumed again. When the same task function

is used for multiple tasks, local variables in the task may be used, but cannot be initialized

individually for every task. embOS offers different options to extend the task context.

2.3.1 Passing one parameter to a task during task creation

Very often it is sufficient to have just one individual parameter passed to a task. Using the

OS_TASK_CREATEEX() or OS_TASK_CreateEx() function to create a task allows passing a

void-pointer to the task. The pointer may point to individual data, or may represent any

data type that can be held within a pointer.

2.3.2 Extending the task context individually at runtime

Sometimes it may be required to have an extended task context for individual tasks to store

global data or special CPU registers such as floating-point registers in the task context.

The standard libraries for file I/O, locale support and others may require task-local stor-

age for specific data like errno and other variables. embOS enables extension of the task

context for individual tasks during runtime by a call of OS_TASK_SetContextExtension().

The sample application file OS_ExtendTaskContext.c delivered in the application samples

folder of embOS demonstrates how the individual task context extension can be used.

2.3.3 Extending the task context by using own task struc-

tures

When complex data is needed for an individual task context, the OS_TASK_CREATEEX() or

OS_TASK_CreateEx() functions may be used, passing a pointer to individual data structures

to the task. Alternatively you may define your own task structure which can be used. Note,

that the first item in the task structure must be an embOS task control structure OS_TASK.

This can be followed by any amount and type of additional data of different types.

The following code shows the example application OS_ExtendedTask.c which is delivered

in the sample application folder of embOS.

/*********************************************************************

* SEGGER Microcontroller GmbH & Co. KG *

* The Embedded Experts *

**********************************************************************

-------------------------- END-OF-HEADER -----------------------------

File : OS_ExtendedTask.c

Purpose : embOS sample program demonstrating the extension of tasks.

#include "RTOS.h"

#include "BSP.h"

/****** Custom task structure with extended task context ************/

typedef struct {

OS_TASK Task; // OS_TASK has to be the first element

OS_TIME Timeout; // Any other data type may be used to extend the context

char* pString; // Any number of elements may be used to extend the context

} MY_APP_TASK;

/****** Static data *************************************************/

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static MY_APP_TASK TCBHP, TCBLP; // Task control blocks

/****** Task function ***********************************************/

static void MyTask(void) {

46 CHAPTER 2 Extending the task context

MY_APP_TASK* pThis;

OS_TIME Timeout;

char* pString;

pThis = (MY_APP_TASK*)OS_TASK_GetID();

while (1) {

Timeout = pThis->Timeout;

pString = pThis->pString;

printf(pString);

OS_TASK_Delay(Timeout);

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

// Create the extended tasks just as normal tasks.

// Note that the first parameter has to be of type OS_TASK

OS_TASK_CREATE(&TCBHP.Task, "HP Task", 100, MyTask, StackHP);

OS_TASK_CREATE(&TCBLP.Task, "LP Task", 50, MyTask, StackLP);

// Give task contexts individual data

TCBHP.Timeout = 200;

TCBHP.pString = "HP task running\n";

TCBLP.Timeout = 500;

TCBLP.pString = "LP task running\n";

OS_Start(); // Start embOS

return 0;

}

/****** End Of File *************************************************/

47 CHAPTER 2 API functions

2.4 API functions

Routine Description

main

Task

ISR

Timer

OS_TASK_AddContextExtension() Adds an additional task context ex-

tension. ●

OS_TASK_AddTerminateHook() Adds a hook (callback) function to

the list of functions which are called

when a task is terminated.

● ●

OS_TASK_CREATE() Creates a new task. ● ●

OS_TASK_Create() Creates a new task. ● ●

OS_TASK_CREATEEX() Creates a new task and passes a pa-

rameter to the task. ● ●

OS_TASK_CreateEx() Creates a new task and passes a pa-

rameter to the task. ● ●

OS_TASK_Delay() Suspends the calling task for a spec-

ified period of time, or waits actively

when called from main().

● ●

OS_TASK_DelayUntil() Suspends the calling task until a

specified time, or waits actively when

called from main().

● ●

OS_TASK_Delayus() Waits for the given time in microsec-

onds. ● ●

OS_TASK_GetName() Returns a pointer to the name of a

task. ●●●●

OS_TASK_GetNumTasks() Returns the number of tasks. ● ● ● ●

OS_TASK_GetPriority() Returns the task priority of a speci-

fied task. ●●●●

OS_TASK_GetSuspendCnt() Returns the suspension count and

thus suspension state of the specified

task.

●●●●

OS_TASK_GetID() Returns a pointer to the task control

block structure of the currently run-

ning task.

●●●●

OS_TASK_GetTimeSliceRem() Returns the remaining time slice val-

ue of a task. ●●●●

OS_TASK_IsTask() Determines whether a task control

block belongs to a valid task. ●●●●

OS_TASK_Index2Ptr() Returns the task control block of the

task with the specified Index. ●●●●

OS_TASK_RemoveAllTerminate-

Hooks()

Removes all hook functions from the

OS_ON_TERMINATE_HOOK list which

contains the list of functions that are

called when a task is terminated.

● ●

OS_TASK_RemoveTerminateHook()

This function removes a hook func-

tion from the OS_ON_TERMINATE_HOOK

list which contains the list of func-

tions that are called when a task is

terminated.

● ●

48 CHAPTER 2 API functions

Routine Description

main

Task

ISR

Timer

OS_TASK_Resume() Decrements the suspend count of the

specified task and resumes it if the

suspend count reaches zero.

● ●

OS_TASK_ResumeAll()

Decrements the suspend count of all

tasks that have a nonzero suspend

count and resumes these tasks when

their respective suspend count reach-

es zero.

●●●●

OS_TASK_SetContextExtension() Makes global variables or processor

registers task-specific. ●

OS_TASK_SetDefaultContextEx-

tension() Sets the default task context exten-

sion for newly created tasks. ● ●

OS_TASK_SetDefaultStartHook() Sets a default hook routine which is

executed before a task starts. ● ●

OS_TASK_SetInitialSuspendCnt() Sets the initial suspend count for

newly created tasks to 1 or 0. ●●●●

OS_TASK_SetName() Allows modification of a task name at

runtime. ●●●●

OS_TASK_SetPriority() Assigns a priority to a specified task. ● ●

OS_TASK_SetTimeSlice() Assigns a specified timeslice period to

a specified task. ●●●●

OS_TASK_Suspend() Suspends the specified task and in-

crements a counter. ●

OS_TASK_SuspendAll() Suspends all tasks except the run-

ning task. ●●●●

OS_TASK_Terminate() Ends (terminates) a task. ● ●

OS_TASK_Wake() Ends delay of a specified task imme-

diately. ●●●

OS_TASK_Yield() Calls the scheduler to force a task

switch. ●

49 CHAPTER 2 API functions

2.4.1 OS_TASK_AddContextExtension()

Description

Adds an additional task context extension. The task context can be extended with

OS_TASK_SetContextExtension() only once. Additional task context extensions can be

added with OS_TASK_AddContextExtension(). The function OS_TASK_AddContextExten-

sion() requires an additional parameter of type OS_EXTEND_TASK_CONTEXT_LINK which is

used to create a task specific linked list of task context extensions.

Prototype

void OS_TASK_AddContextExtension

(OS_EXTEND_TASK_CONTEXT_LINK* pExtendContextLink,

OS_CONST_PTR OS_EXTEND_TASK_CONTEXT *pExtendContext);

Parameters

Parameter Description

pExtendContextLink Pointer to the OS_EXTEND_TASK_CONTEXT_LINK structure.

pExtendContext

Pointer to the OS_EXTEND_TASK_CONTEXT structure which

contains the addresses of the specific save and restore func-

tions that save and restore the extended task context during

task switches.

Additional information

The object of type OS_EXTEND_TASK_CONTEXT_LINK is task specific and must only be used

for one task. It can be located e.g. on the task stack. OS_TASK_AddContextExtension()

must only be used when OS_TASK_SetContextExtension() has been called before.

Example

static void HPTask(void) {

OS_EXTEND_TASK_CONTEXT_LINK p;

// Extend task context by VFP registers

OS_TASK_SetContextExtension(&_SaveRestoreVFP);

// Extend task context by global variable

OS_TASK_AddContextExtension(&p, &_SaveRestoreGlobalVar);

a = 1.2;

while (1) {

b = 3 * a;

GlobalVar = 1;

OS_TASK_Delay(10);

}

50 CHAPTER 2 API functions

2.4.2 OS_TASK_AddTerminateHook()

Description

Adds a hook (callback) function to the list of functions which are called when a task is

terminated.

Prototype

void OS_TASK_AddTerminateHook(OS_ON_TERMINATE_HOOK* pHook,

OS_ON_TERMINATE_FUNC* pfUser);

Parameters

Parameter Description

pHook Pointer to a variable of type OS_ON_TERMINATE_HOOK which

will be inserted into the linked list of functions to be called

during OS_TASK_Terminate().

pfUser Pointer to the function of type OS_TERMINATE_FUNC which

shall be called when a task is terminated.

Additional information

For some applications, it may be useful to allocate memory or objects specific to tasks. For

other applications, it may be useful to have task-specific information on the stack. When a

task is terminated, the task-specific objects may become invalid. A callback function may

be hooked into OS_TASK_Terminate() by calling OS_TASK_AddTerminateHook() to allow

the application to invalidate all task-specific objects before the task is terminated. The

callback function of type OS_ON_TERMINATE_FUNC receives the ID of the terminated task as

its parameter. OS_ON_TERMINATE_FUNC is defined as:

typedef void OS_ON_TERMINATE_FUNC(OS_CONST_PTR OS_TASK* pTask);

Note

The variable of type OS_ON_TERMINATE_HOOK must reside in memory as a global or

static variable. It may be located on a task stack, as local variable, but it must not be

located on any stack of any task that might be terminated.

Example

OS_ON_TERMINATE_HOOK _TerminateHook;

void TerminateHookFunc(OS_CONST_PTR OS_TASK* pTask) {

// This function is executed upon calling OS_TASK_Terminate().

if (pTask == &MyTask) {

free(MytaskBuffer);

}

...

int main(void) {

OS_TASK_AddTerminateHook(&_TerminateHook, TerminateHookFunc);

...

}

51 CHAPTER 2 API functions

2.4.3 OS_TASK_CREATE()

Description

Creates a new task.

Prototype

void OS_TASK_CREATE(OS_TASK* pTask,

char* pName,

OS_PRIO Priority,

void* pRoutine,

void* pStack);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

pName Pointer to the name of the task. Can be NULL (or 0) if not used.

Priority

Priority of the task. Must be within the following range:

1 ≤ Priority ≤ 28-1 = 0xFF for 8/16 bit CPUs

1 ≤ Priority ≤ 232-1 = 0xFFFFFFFF for 32 bit CPUs

Higher values indicate higher priorities. The type OS_PRIO is defined

as 32 bit value for 32 bit CPUs and 8 bit value for 8 or 16 bit CPUs by

default.

pRoutine Pointer to a function that should run as the task body.

pStack Pointer to an area of memory in RAM that will serve as stack area for

the task. The size of this block of memory determines the size of the

stack area.

Additional information

OS_TASK_CREATE() is a macro which calls an OS library function. It creates a task and

makes it ready for execution by placing it into the READY state. The newly created task will

be activated by the scheduler as soon as there is no other task with higher priority in the

READY state. If there is another task with the same priority, the new task will be placed

immediately before it. This macro is normally used for creating a task instead of the function

call OS_TASK_Create() because it has fewer parameters and is therefore easier to use.

OS_TASK_CREATE() can be called either from main() during initialization or from any other

task. The recommended strategy is to create all tasks during initialization in main() to

keep the structure of your tasks easy to understand. The absolute value of Priority is of no

importance, only the value in comparison to the priorities of other tasks matters.

OS_TASK_CREATE() determines the size of the stack automatically, using sizeof(). This is

possible only if the memory area has been defined at compile time.

Note

The stack that you define must reside in an area that the CPU can address as stack.

Most CPUs cannot use the entire memory area as stack and require the stack to be

aligned to a multiple of the processor word size. The task stack cannot be shared

between multiple tasks and must be assigned to one task only. The memory used as

task stack cannot be used for other purposes unless the task is terminated.

52 CHAPTER 2 API functions

Example

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void HPTask(void) {

while (1) {

OS_TASK_Delay(50);

}

static void LPTask(void) {

while (1) {

OS_TASK_Delay(200);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

53 CHAPTER 2 API functions

2.4.4 OS_TASK_Create()

Description

Creates a new task.

Prototype

void OS_TASK_Create( OS_TASK* pTask,

const char* pName,

OS_PRIO Priority,

void ( *pRoutine)(),

void OS_STACKPTR *pStack,

OS_UINT StackSize,

OS_UINT TimeSlice);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

pName

Pointer to the name of the task. Can be NULL (or 0) if not

used. When using an embOS build without task name sup-

port, this parameter does not exist and must be omitted.

The embOS OS_LIBMODE_XR libraries do not support task

names.

Priority

Priority of the task. Must be within the following range:

1 ≤ Priority ≤ 28 - 1 = 0xFF for 8/16 bit CPUs

1 ≤ Priority ≤ 232 - 1 = 0xFFFFFFFF for 32 bit CPUs

Higher values indicate higher priorities. The type OS_PRIO is

defined as a 32 bit value for 32 bit CPUs and as an 8 bit val-

ue for 8 or 16 bit CPUs by default.

pRoutine Pointer to a function that should run as the task body.

pStack Pointer to an area of memory in RAM that will serve as stack

area for the task. The size of this block of memory deter-

mines the size of the stack area.

StackSize Size of stack in bytes.

TimeSlice

Time slice value for round-robin scheduling. Has an effect

only if other tasks are running at the same priority. It de-

notes the time (in embOS embOS system ticks) that the

task will run before it suspends, and must be in the following

range: 0 ≤ TimeSlice ≤ 255. When using an embOS build

without round-robin support, this parameter does not exist

and must be omitted. The embOS OS_LIBMODE_XR libraries

do not support round-robin and time slice.

Additional information

This function works the same way as OS_TASK_CREATE(), except that all parameters of

the task can be specified. The task can be dynamically created because the stack size is

not calculated automatically as it is with the macro. A time slice value of zero is allowed

and disables round-robin task switches. (see sample in chapter Disabling preemptive task

switches for tasks of equal priority on page 44)

54 CHAPTER 2 API functions

Note

The stack that you define must reside in an area that the CPU can address as stack.

Most CPUs cannot use the entire memory area as stack and require the stack to be

aligned to a multiple of the processor word size. The task stack cannot be shared

between multiple tasks and must be assigned to one task only. The memory used as

task stack cannot be used for other purposes unless the task is terminated.

Example

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void HPTask(void) {

while (1) {

OS_TASK_Delay(50);

}

static void LPTask(void) {

while (1) {

OS_TASK_Delay(200);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_Create(&TCBHP, "HP Task", 100, HPTask, StackHP, sizeof(StackHP), 2);

OS_TASK_Create(&TCBLP, "LP Task", 50, LPTask, StackLP, sizeof(StackLP), 2);

OS_Start(); // Start embOS

return 0;

}

55 CHAPTER 2 API functions

2.4.5 OS_TASK_CREATEEX()

Description

Creates a new task and passes a parameter to the task.

Prototype

void OS_TASK_CREATEEX(OS_TASK* pTask,

char* pName,

OS_PRIO Priority,

void* pRoutine,

void* pStack,

void* pContext);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

pName Pointer to the name of the task. Can be NULL (or 0) if not used.

Priority

Priority of the task. Must be within the following range:

1 ≤ Priority ≤ 28-1 = 0xFF for 8/16 bit CPUs

1 ≤ Priority ≤ 232-1 = 0xFFFFFFFF for 32 bit CPUs

Higher values indicate higher priorities. The type OS_PRIO is defined

as 32 bit value for 32 bit CPUs and 8 bit value for 8 or 16 bit CPUs by

default.

pRoutine Pointer to a function that should run as the task body.

pStack Pointer to an area of memory in RAM that will serve as stack area for

the task. The size of this block of memory determines the size of the

stack area.

pContext Parameter passed to the created task function.

Additional information

OS_TASK_CREATEEX() is a macro calling an embOS library function. It works like

OS_TASK_CREATE() but allows passing a parameter to the task. Using a void pointer as an

additional parameter gives the flexibility to pass any kind of data to the task function.

Note

The stack that you define must reside in an area that the CPU can address as stack.

Most CPUs cannot use the entire memory area as stack and require the stack to be

aligned to a multiple of the processor word size. The task stack cannot be shared

between multiple tasks and must be assigned to one task only. The memory used as

task stack cannot be used for other purposes unless the task is terminated.

56 CHAPTER 2 API functions

Example

The following example is delivered in the Application folder of embOS.

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void Task(void* pContext) {

while (1) {

OS_TASK_Delay((int)pContext);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATEEX(&TCBHP, "HP Task", 100, Task, StackHP, (void*) 50);

OS_TASK_CREATEEX(&TCBLP, "LP Task", 50, Task, StackLP, (void*)200);

OS_Start(); // Start embOS

return 0;

}

57 CHAPTER 2 API functions

2.4.6 OS_TASK_CreateEx()

Description

Creates a new task and passes a parameter to the task.

Prototype

void OS_TASK_CreateEx( OS_TASK* pTask,

const char* pName,

OS_PRIO Priority,

void ( *pRoutine)(void * pVoid ),

void OS_STACKPTR *pStack,

OS_UINT StackSize,

OS_UINT TimeSlice,

void* pContext);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

pName

Pointer to the name of the task. Can be NULL (or 0) if not

used. When using an embOS build without task name sup-

port, this parameter does not exist and must be omitted.

The embOS OS_LIBMODE_XR libraries do not support task

names.

Priority

Priority of the task. Must be within the following range:

1 ≤ Priority ≤ 28 - 1 = 0xFF for 8/16 bit CPUs

1 ≤ Priority ≤ 232 - 1 = 0xFFFFFFFF for 32 bit CPUs

Higher values indicate higher priorities. The type OS_PRIO is

defined as a 32 bit value for 32 bit CPUs and as an 8 bit val-

ue for 8 or 16 bit CPUs by default.

pRoutine Pointer to a function that should run as the task body.

pStack Pointer to an area of memory in RAM that will serve as stack

area for the task. The size of this block of memory deter-

mines the size of the stack area.

StackSize Size of stack in bytes.

TimeSlice

Time slice value for round-robin scheduling. Has an effect

only if other tasks are running at the same priority. It de-

notes the time (in embOS embOS system ticks) that the

task will run before it suspends, and must be in the following

range: 0 ≤ TimeSlice ≤ 255. When using an embOS build

without round-robin support, this parameter does not exist

and must be omitted. The embOS OS_LIBMODE_XR libraries

do not support round-robin and time slice.

pContext Parameter passed to the created task.

Additional information

This function works the same way as OS_TASK_CREATE(), except that all parameters of

the task can be specified. The task can be dynamically created because the stack size is

not calculated automatically as it is with the macro. A time slice value of zero is allowed

and disables round-robin task switches. (see sample in chapter Disabling preemptive task

switches for tasks of equal priority on page 44)

Note

The stack that you define must reside in an area that the CPU can address as stack.

Most CPUs cannot use the entire memory area as stack and require the stack to be

58 CHAPTER 2 API functions

aligned to a multiple of the processor word size. The task stack cannot be shared

between multiple tasks and must be assigned to one task only. The memory used as

task stack cannot be used for other purposes unless the task is terminated.

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void Task(void* pContext) {

while (1) {

OS_TASK_Delay((int)pContext);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CreateEx(&TCBHP, "HP Task", 100, Task,

StackHP, sizeof(StackHP), 2, (void*) 50);

OS_TASK_CreateEx(&TCBLP, "LP Task", 50, Task,

StackLP, sizeof(StackLP), 2, (void*)200);

OS_Start(); // Start embOS

return 0;

}

59 CHAPTER 2 API functions

2.4.7 OS_TASK_Delay()

Description

Suspends the calling task for a specified period of time, or waits actively when called from

main().

Prototype

void OS_TASK_Delay(OS_TIME t);

Parameters

Parameter Description

Time interval to delay. Must be within the following range:

0 ≤ t ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs

0 ≤ t ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs

Please note that these are signed values.

Additional information

The parameter t specifies the time interval in system ticks during which the task is sus-

pended. The actual delay will be in the following range: t - 1 ≤ delay ≤ t, depending on

when the interrupt for the scheduler occurs. After the expiration of the delay, the task is

made ready and activated according to the rules of the scheduler. A delay can be ended

prematurely by another task or by an interrupt handler calling OS_TASK_Wake().

If OS_TASK_Delay() is called from main(), it will actively wait for the timeout to expire.

Therefore, interrupts must be enabled.

Example

void Hello(void) {

printf("Hello");

printf("The next output will occur in 5000 system ticks");

OS_TASK_Delay(5000);

printf("Delay is over");

}

60 CHAPTER 2 API functions

2.4.8 OS_TASK_DelayUntil()

Description

Suspends the calling task until a specified time, or waits actively when called from main().

Prototype

void OS_TASK_DelayUntil(OS_TIME t);

Parameters

Parameter Description

Time to delay until. Must be within the following range:

0 ≤ t ≤ 216 - 1 = 0xFFFF for 8/16 bit CPUs

0 ≤ t ≤ 232 - 1 = 0xFFFFFFFF for 32 bit CPUs

Also, the following additional condition must be met:

1 ≤ (t - OS_GLOBAL.Time) ≤ 215 - 1 = 0x7FFF for 8/16 bit

CPUs

1 ≤ (t - OS_GLOBAL.Time) ≤ 231 - 1 = 0x7FFFFFFF for 32 bit

CPUs

Please note that these are signed values.

Additional information

OS_TASK_DelayUntil() suspends the calling task until the global time-variable OS_Glob-

al.Time (see OS_Global.Time on page 464) reaches the specified value. The main ad-

vantage of this function is that it avoids potentially accumulating delays. The additional

condition towards parameter t ensures proper behavior even when a overflow of the em-

bOS system tick timer occurs.

If OS_TASK_DelayUntil() is called from main(), it will actively wait for the timeout to

expire. Therefore, interrupts must be enabled.

Example

int sec, min;

void TaskShowTime(void) {

OS_TIME t0;

t0 = OS_TIME_GetTicks();

while (1) {

ShowTime(); // Routine to display time

t0 += 1000;

OS_TASK_DelayUntil(t0);

if (sec < 59) {

sec++;

} else {

sec = 0;

min++;

}

In the example above, using OS_TASK_Delay() could lead to accumulating delays and would

cause the simple “clock” to be slow. Using OS_TASK_DelayUntil() instead avoids accumu-

lating delays.

61 CHAPTER 2 API functions

2.4.9 OS_TASK_Delayus()

Description

Waits for the given time in microseconds.

Prototype

void OS_TASK_Delayus(OS_U16 us);

Parameters

Parameter Description

Number of microseconds to delay. Must be within the follow-

ing range:

1 ≤ us ≤ 215 - 1 = 0x7FFF.

Please note that these are signed values.

Additional information

This function can be used for short delays. OS_TASK_Delayus() must only be called with

interrupts enabled and after OS_Init() and OS_InitHW() have been called. This only works

when the embOS system timer is running. An debug build of OS_TASK_Delayus() checks

whether interrupts are enabled and calls OS_Error() if they are not.

OS_TASK_Delayus() does not block task switches and does not block interrupts. Therefore,

the delay may not be accurate because the function may be interrupted for an undefined

time. The delay duration therefore is a minimum delay.

OS_TASK_Delayus() does not suspend the calling task, thus all tasks with lower priority

can not interrupt OS_TASK_Delayus() and will not be executed before OS_TASK_Delayus()

returns.

Example

void Hello(void) {

printf("Hello");

printf("The next output will occur in 500 microseconds");

OS_TASK_Delayus(500);

printf("Delay is over");

}

62 CHAPTER 2 API functions

2.4.10 OS_TASK_GetName()

Description

Returns a pointer to the name of a task.

Prototype

char *OS_TASK_GetName(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

Return value

A pointer to the name of the task. NULL indicates that the task has no name.

When using an embOS build without task name support, OS_TASK_GetName() returns “n/

a” in any case. The embOS OS_LIBMODE_XR libraries do not support task names.

Additional information

If pTask is NULL, the function returns the name of the running task. If there is no currently

running task, the return value is “OS_Idle()”. If pTask is not NULL and does not specify a

valid task, a debug build of embOS calls OS_Error(). The release build of embOS cannot

check the validity of pTask and may therefore return invalid values if pTask does not specify

a valid task.

Example

void PrintTaskName(void) {

char* s;

s = OS_TASK_GetName(NULL);

printf("Task name: %s\n", s);

}

63 CHAPTER 2 API functions

2.4.11 OS_TASK_GetNumTasks()

Description

Returns the number of tasks.

Prototype

int OS_TASK_GetNumTasks(void);

Return value

Number of tasks.

Example

void PrintNumberOfTasks(void) {

int NumTasks;

NumTasks = OS_TASK_GetNumTasks();

printf("Number of tasks %d\n", NumTasks);

}

64 CHAPTER 2 API functions

2.4.12 OS_TASK_GetPriority()

Description

Returns the task priority of a specified task.

Prototype

OS_PRIO OS_TASK_GetPriority(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask Pointer to a task control block structure or NULL for current

task.

Return value

Priority of the specified task (range 1 to 255 for 8/16 bit CPUs and up to 4294967295 for

32 bit CPUs).

Additional information

If pTask is NULL, the function returns the priority of the currently running task. If pTask

does not specify a valid task, the debug build of embOS calls OS_Error(). The release build

of embOS cannot check the validity of pTask and may therefore return invalid values if

pTask does not specify a valid task.

Note

This function can be called from within an interrupt handler with OS_TASK_GetPrior-

ity(NULL) but if the handler interrupts OS_Idle() no task is currently running and

no valid task is specified. The debug build of embOS calls OS_Error() in this case.

We suggest to call OS_TASK_GetPriority() from an interrupt handler with a pointer

to a valid task control block only.

Example

void PrintPriority(const OS_TASK* pTask) {

OS_PRIO Prio;

Prio = OS_TASK_GetPriority(pTask);

printf("Priority of task 0x%x = %u\n", pTask, Prio);

}

65 CHAPTER 2 API functions

2.4.13 OS_TASK_GetSuspendCnt()

Description

Returns the suspension count and thus suspension state of the specified task. This function

may be used to examine whether a task is suspended by previous calls of OS_TASK_Sus-

pend().

Prototype

OS_U8 OS_TASK_GetSuspendCnt(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask Pointer to task control block structure.

Return value

Suspension count of the specified task.

= 0 Task is not suspended.

> 0 Task is suspended by at least one call of OS_TASK_Suspend().

Additional information

If pTask does not specify a valid task, the debug build of embOS calls OS_Error(). The

release build of embOS cannot check the validity of pTask and may therefore return invalid

values if pTask does not specify a valid task. When tasks are created and terminated dy-

namically, OS_TASK_IsTask() may be called prior to calling OS_TASK_GetSuspendCnt() to

determine whether a task is valid. The returned value can be used to resume a suspended

task by calling OS_TASK_Resume() as often as indicated by the returned value.

Example

void ResumeTask(OS_TASK* pTask) {

OS_U8 SuspendCnt;

SuspendCnt = OS_TASK_GetSuspendCnt(pTask);

while (SuspendCnt > 0u) {

OS_TASK_Resume(pTask); // May cause a task switch

SuspendCnt--;

}

66 CHAPTER 2 API functions

2.4.14 OS_TASK_GetID()

Description

Returns a pointer to the task control block structure of the currently running task. This

pointer is unique for the task and is used as a task Id.

Prototype

OS_TASK* OS_TASK_GetID(void);

Return value

A pointer to the task control block. NULL indicates that no task is executing.

Additional information

This function may be used for determining which task is executing. This may be helpful if

the reaction of any function depends on the currently running task.

Example

void PrintCurrentTaskID(void) {

OS_TASK* pTask;

pTask = OS_TASK_GetID();

printf("Task ID 0x%x\n", pTask);

}

67 CHAPTER 2 API functions

2.4.15 OS_TASK_GetTimeSliceRem()

Description

Returns the remaining time slice value of a task.

Prototype

OS_U8 OS_TASK_GetTimeSliceRem(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

Return value

Remaining time slice value of the task.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task. The release

build of embOS cannot check the validity of pTask and may therefore return invalid values

if pTask does not specify a valid task.

The function is unavailable when using an embOS build without round-robin support. The

embOS OS_LIBMODE_XR libraries do not support round-robin. In that case OS_TASK_Get-

TimeSliceRem() returns zero.

Example

void PrintRemainingTimeSlices(void) {

OS_U8 slices;

slices = OS_TASK_GetTimeSliceRem(NULL);

printf("Remaining Time Slices: %d\n", slices);

}

68 CHAPTER 2 API functions

2.4.16 OS_TASK_IsTask()

Description

Determines whether a task control block belongs to a valid task.

Prototype

OS_BOOL OS_TASK_IsTask(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

Return value

0 TCB is not used by any task.

1 TCB is used by a task.

Additional information

This function checks if the specified task is present in the internal task list. When a task is

terminated it is removed from the internal task list. In applications that create and terminate

tasks dynamically, this function may be useful to determine whether the task control block

and stack for one task may be reused for another task.

Example

void PrintTCBStatus(OS_TASK* pTask) {

OS_BOOL b;

b = OS_TASK_IsTask(pTask);

if (b == 0) {

printf("TCB can be reused for another task.\n");

} else {

printf("TCB refers to a valid task.\n");

}

69 CHAPTER 2 API functions

2.4.17 OS_TASK_Index2Ptr()

Description

Returns the task control block of the task with the specified Index.

Prototype

OS_TASK *OS_TASK_Index2Ptr(int TaskIndex);

Parameters

Parameter Description

TaskIndex Index of a task control block in the task list.

This is a zero based index. TaskIndex 0 identifies the first

task control block.

Return value

= NULL No task control block with this index found.

≠ NULL Pointer to the task control block with the index TaskIndex.

Example

void PrintTaskName(int TaskIndex) {

OS_TASK* pTask;

pTask = OS_TASK_Index2Ptr(TaskIndex);

if (pTask != NULL) {

printf("%s", pTask->Name);

}

void HPTask(void) {

// Print the task name of the first task in the task list

PrintTaskName(0);

while (1) {

OS_TASK_Delay(100);

}

70 CHAPTER 2 API functions

2.4.18 OS_TASK_RemoveAllTerminateHooks()

Description

Removes all hook functions from the OS_ON_TERMINATE_HOOK list which contains the list of

functions that are called when a task is terminated.

Prototype

void OS_TASK_RemoveAllTerminateHooks(void);

Additional information

OS_TASK_RemoveAllTerminateHooks() removes all hook functions which were previously

added by OS_TASK_AddTerminateHook().

Example

OS_ON_TERMINATE_HOOK _TerminateHook;

void TerminateHookFunc(OS_CONST_PTR OS_TASK* pTask) {

// This function is called when OS_TASK_Terminate() is called.

if (pTask == &MyTask) {

free(MytaskBuffer);

}

...

int main(void) {

OS_TASK_AddTerminateHook(&_TerminateHook, TerminateHookFunc);

OS_TASK_RemoveAllTerminateHooks();

...

}

71 CHAPTER 2 API functions

2.4.19 OS_TASK_RemoveTerminateHook()

Description

This function removes a hook function from the OS_ON_TERMINATE_HOOK list which contains

the list of functions that are called when a task is terminated.

Prototype

void OS_TASK_RemoveTerminateHook(OS_CONST_PTR OS_ON_TERMINATE_HOOK *pHook);

Parameters

Parameter Description

pHook Pointer to a variable of type OS_ON_TERMINATE_HOOK.

Additional information

OS_TASK_RemoveTerminateHook() removes the specified hook function which was previ-

ously added by OS_TASK_AddTerminateHook().

Example

OS_ON_TERMINATE_HOOK _TerminateHook;

void TerminateHookFunc(OS_CONST_PTR OS_TASK* pTask) {

// This function is called when OS_TASK_Terminate() is called.

if (pTask == &MyTask) {

free(MytaskBuffer);

}

...

int main(void) {

OS_TASK_AddTerminateHook(&_TerminateHook, TerminateHookFunc);

OS_TASK_RemoveTerminateHook(&_TerminateHook);

...

}

72 CHAPTER 2 API functions

2.4.20 OS_TASK_Resume()

Description

Decrements the suspend count of the specified task and resumes it if the suspend count

reaches zero.

Prototype

void OS_TASK_Resume(OS_TASK* pTask);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

Additional information

The specified task’s suspend count is decremented. When the resulting value is zero, the

execution of the specified task is resumed. If the task is not blocked by other task blocking

mechanisms, the task is placed in the READY state and continues operation according to the

rules of the scheduler. In debug builds of embOS, OS_TASK_Resume() checks the suspend

count of the specified task. If the suspend count is zero when OS_TASK_Resume() is called,

OS_Error() is called with error OS_ERR_RESUME_BEFORE_SUSPEND.

Example

Please refer to the example of OS_TASK_Suspend().

73 CHAPTER 2 API functions

2.4.21 OS_TASK_ResumeAll()

Description

Decrements the suspend count of all tasks that have a nonzero suspend count and resumes

these tasks when their respective suspend count reaches zero.

Prototype

void OS_TASK_ResumeAll(void);

Additional information

This function may be helpful to synchronize or start multiple tasks at the same time. The

function resumes all tasks, no specific task must be addressed. The function may be used

together with the functions OS_TASK_SuspendAll() and OS_TASK_SetInitialSuspendCn-

t().

The function may cause a task switch when a task with higher priority than the calling task

is resumed. The task switch will be executed after all suspended tasks are resumed.

The function may be called even when no task is suspended.

Example

Please refer to the example of OS_TASK_SetInitialSuspendCnt().

74 CHAPTER 2 API functions

2.4.22 OS_TASK_SetContextExtension()

Description

Makes global variables or processor registers task-specific. The function may be used for

a variety of purposes. Typical applications are:

• Global variables such as “errno” in the C library, making the C-lib functions thread-safe.

• Additional, optional CPU / registers such as MAC / EMAC registers (multiply and

accumulate unit) if they are not saved in the task context per default.

• Coprocessor registers such as registers of a VFP (floating-point coprocessor).

• Data registers of an additional hardware unit such as a CRC calculation unit.

This allows the user to extend the task context as required. A major advantage is that

the task extension is task-specific. This means that the additional information (such as

floating-point registers) needs to be saved only by tasks that actually use these registers.

The advantage is that the task switching time of other tasks is not affected. The same is

true for the required stack space: Additional stack space is required only for the tasks which

actually save the additional registers.

Prototype

void OS_TASK_SetContextExtension

(OS_CONST_PTR OS_EXTEND_TASK_CONTEXT *pExtendContext);

Parameters

Parameter Description

pExtendContext

Pointer to the OS_EXTEND_TASK_CONTEXT structure which

contains the addresses of the specific save and restore func-

tions that save and restore the extended task context during

task switches.

Additional information

The save and restore functions must be declared according the function type used in the

structure. The sample below shows how the task stack must be addressed to save and

restore the extended task context.

OS_TASK_SetContextExtension() is not available in the XR libraries.

Note

The task context can be extended only once per task with OS_TASK_SetContextEx-

tension(). The function must not be called multple times for one task. Additional task

context extensions can be set with OS_TASK_AddContextExtension().

The OS_EXTEND_TASK_CONTEXT structure is defined as follows:

typedef struct OS_EXTEND_TASK_CONTEXT {

void* (*pfSave) ( void* pStack);

void* (*pfRestore)(const void* pStack);

} OS_EXTEND_TASK_CONTEXT;

75 CHAPTER 2 API functions

Note

In embOS V4.16 and earlier the OS_EXTEND_TASK_CONTEXT structure was defined as

follows:

typedef struct OS_EXTEND_TASK_CONTEXT_STRUCT {

void (*pfSave) ( void OS_STACKPTR * pStack);

void (*pfRestore)(const void OS_STACKPTR * pStack);

} OS_EXTEND_TASK_CONTEXT;

The Save/Restore functions did not return the stack pointer. When updating from

embOS V4.16 and earlier to embOS V4.20 and later please update your Save/Restore

functions accordingly.

76 CHAPTER 2 API functions

Example

The following example is delivered in the Application folder of embOS.

-------------------------- END-OF-HEADER -----------------------------

File : OS_ExtendTaskContext.c

Purpose : embOS sample program demonstrating the dynamic extension of

tasks' contexts. This is done by adding a global variable to

the task context of certain tasks.

#include "RTOS.h"

/*********************************************************************

* Types, local

**********************************************************************

// Custom structure with task context extension.

// In this case, the extended task context consists of just

// a single member, which is a global variable.

typedef struct {

int GlobalVar;

} CONTEXT_EXTENSION;

/*********************************************************************

* Static data

**********************************************************************

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static int GlobalVar;

/*********************************************************************

* Local functions

**********************************************************************

/*********************************************************************

* _Save()

* Function description

* This function saves an extended task context.

static void OS_STACKPTR* _Save(void OS_STACKPTR* pStack) {

CONTEXT_EXTENSION* p;

// Create pointer to our structure

p = ((CONTEXT_EXTENSION*)pStack) - (1 - OS_STACK_AT_BOTTOM);

// Save all members of the structure

p->GlobalVar = GlobalVar;

return (void OS_STACKPTR*)p;

}

77 CHAPTER 2 API functions

/*********************************************************************

* _Restore()

* Function description

* This function restores an extended task context.

static void OS_STACKPTR* _Restore(const void OS_STACKPTR* pStack) {

const CONTEXT_EXTENSION* p;

// Create pointer to our structure

p = ((const CONTEXT_EXTENSION *)pStack) - (1 - OS_STACK_AT_BOTTOM);

// Restore all members of the structure

GlobalVar = p->GlobalVar;

return (void OS_STACKPTR*)p;

}

/*********************************************************************

* Public API structure

const OS_EXTEND_TASK_CONTEXT _SaveRestore = {

_Save, // Function pointer to save the task context

_Restore // Function pointer to restore the task context

};

/*********************************************************************

* HPTask()

* Function description

* During the execution of this function, the thread-specific

* global variable GlobalVar always has the same value of 1.

static void HPTask(void) {

OS_TASK_SetContextExtension(&_SaveRestore);

GlobalVar = 1;

while (1) {

OS_TASK_Delay(10);

}

/*********************************************************************

* LPTask()

* Function description

* During the execution of this function, the thread-specific

* global variable GlobalVar always has the same value of 2.

static void LPTask(void) {

OS_TASK_SetContextExtension(&_SaveRestore);

GlobalVar = 2;

while (1) {

OS_TASK_Delay(50);

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

78 CHAPTER 2 API functions

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

79 CHAPTER 2 API functions

2.4.23 OS_TASK_SetDefaultContextExtension()

Description

Sets the default task context extension for newly created tasks.

Prototype

void OS_TASK_SetDefaultContextExtension

(OS_CONST_PTR OS_EXTEND_TASK_CONTEXT *pExtendContext);

Parameters

Parameter Description

pExtendContext

Pointer to the OS_EXTEND_TASK_CONTEXT structure which

contains the addresses of the specific save and restore func-

tions that save and restore the extended task context during

task switches.

Additional information

After calling this function all newly started tasks will automatically use this context exten-

sion. The same task context extension is used for all tasks.

Example

extern const OS_EXTEND_TASK_CONTEXT _SaveRestore;

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_SetDefaultContextExtension(&_SaveRestore);

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

80 CHAPTER 2 API functions

2.4.24 OS_TASK_SetDefaultStartHook()

Description

Sets a default hook routine which is executed before a task starts. May be used to perform

additional initialization for newly created tasks.

Prototype

void OS_TASK_SetDefaultStartHook(voidRoutine* pfHook);

Parameters

Parameter Description

pfHook Pointer to the hook routine.

If NULL is passed no hook routine gets executed.

Additional information

After calling OS_TASK_SetDefaultStartHook() all newly created tasks will automatically

call this hook routine before the tasks are started for the first time. The same hook function

is used for all tasks.

Example

void _HookRoutine(void) { // This routine is automatically executed before

DoSomeThing(); // HPTask() gets executed

}

void HPTask(void) {

while (1) {

OS_TASK_Delay(10);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_SetDefaultStartHook(_HookRoutine); // Set task start hook routine

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_Start(); // Start embOS

return 0;

}

81 CHAPTER 2 API functions

2.4.25 OS_TASK_SetInitialSuspendCnt()

Description

Sets the initial suspend count for newly created tasks to 1 or 0. May be used to create

tasks which are initially suspended.

Prototype

void OS_TASK_SetInitialSuspendCnt(OS_U8 SuspendCnt);

Parameters

Parameter Description

SuspendCnt 1: Tasks will be created in suspended state.

0: Tasks will be created normally, unsuspended.

Additional information

Can be called at any time from main(), any task, ISR or software timer. After calling this

function with nonzero SuspendCnt, all newly created tasks will be automatically suspended

with a suspend count of one. This function may be used to inhibit further task switches,

which may be useful during system initailization.

Note

When this function is called from main() to initialize all tasks in suspended state, at

least one task must be resumed before the system is started by a call of OS_Start().

The initial suspend count should be reset to allow normal creation of tasks before the

system is started.

Example

// High priority task started first after OS_Start().

void InitTask(void) {

OS_TASK_SuspendAll();

// Prevent execution of all other existing tasks.

OS_TASK_SetInitialSuspendCnt(1);

// Prevent execution of subsequently created tasks.

... // New tasks may be created, but will not execute.

... // Even when InitTask() blocks itself, no other task may execute.

OS_TASK_SetInitialSuspendCnt(0); // Reset initial suspend count for new tasks.

OS_TASK_ResumeAll();

// Resume all tasks that were blocked before or

// were created in suspended state. May cause a

// task switch.

while (1) {

... // Do the normal work.

}

82 CHAPTER 2 API functions

2.4.26 OS_TASK_SetName()

Description

Allows modification of a task name at runtime.

Prototype

void OS_TASK_SetName( OS_TASK* pTask,

const char* s);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

sPointer to a null-terminated string which is used as task

name.

Additional information

If NULL is passed for pTask, the currently running task is modified. However, NULL must

not be passed for pTask from main(), from a timer callback or from an interrupt handler.

A debug build of embOS will call OS_Error() in case pTask does not indicate a valid task.

When using an embOS build without task name support, OS_TASK_SetName() performs no

modifications at all. The embOS OS_LIBMODE_XR libraries do not support task names.

Example

void Task(void) {

OS_TASK_SetName(NULL, "Initializer Task");

while (1) {

OS_TASK_Delay(100);

}

83 CHAPTER 2 API functions

2.4.27 OS_TASK_SetPriority()

Description

Assigns a priority to a specified task.

Prototype

void OS_TASK_SetPriority(OS_TASK* pTask,

OS_PRIO Priority);

Parameters

Parameter Description

pTask Pointer to a task control block structure or NULL for current

task.

Priority

Priority of the task. Must be within the following range:

1 ≤ Priority ≤ 28 - 1 = 0xFF for 8/16 bit CPUs

1 ≤ Priority ≤ 232 - 1 = 0xFFFFFFFF for 32 bit CPUs

Higher values indicate higher priorities. The type OS_PRIO is

defined as 32 bit value for 32 bit CPUs and 8 bit value for 8

or 16 bit CPUs per default.

Additional information

If NULL is passed for pTask, the currently running task is modified. However, NULL must

not be passed for pTask from main(). A debug build of embOS will call OS_Error() in case

pTask does not indicate a valid task.

Calling this function might lead to an immediate task switch.

Example

void Task(void) {

OS_TASK_SetPriority(NULL, 20); // Change priority of this task to 20.

while (1) {

OS_TASK_Delay(100);

}

84 CHAPTER 2 API functions

2.4.28 OS_TASK_SetTimeSlice()

Description

Assigns a specified timeslice period to a specified task.

Prototype

OS_U8 OS_TASK_SetTimeSlice(OS_TASK* pTask,

OS_U8 TimeSlice);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

TimeSlice New time slice period for the task. Must be within the follow-

ing range:

0 ≤ TimeSlice ≤ 255.

Return value

Previous time slice period of the task.

Additional information

If NULL is passed for pTask, the currently running task is modified. However, NULL must not

be passed for pTask from main(), a timer callback or from an interrupt handler. A debug

build of embOS will call OS_Error() in case pTask does not indicate a valid task.

Setting the time slice period only affects tasks running in round-robin mode. The new time

slice period is interpreted as a reload value: It is used with the next activation of the task,

but does does not affect the remaining time slice of a running task.

A time slice value of zero is allowed, but disables round-robin task switches (see Disabling

preemptive task switches for tasks of equal priority on page 44).

The function is unavailable when using an embOS build without round-robin support. The

embOS OS_LIBMODE_XR libraries do not support round-robin. In that case OS_TASK_Set-

TimeSlice() does nothing and returns zero.

Example

void Task(void) {

OS_TASK_SetTimeSlice(NULL, 4); // Give this task a higher time slice

while (1) {

OS_TASK_Delay(100);

}

85 CHAPTER 2 API functions

2.4.29 OS_TASK_Suspend()

Description

Suspends the specified task and increments a counter.

Prototype

void OS_TASK_Suspend(OS_TASK* pTask);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

Additional information

If pTask is NULL, the current task suspends. If the function succeeds, execution of the

specified task is suspended and the task’s suspend count is incremented. The specified task

will be suspended immediately. It can only be restarted by a call of OS_TASK_Resume().

Every task has a suspend count with a maximum value of OS_MAX_SUSPEND_CNT. If the

suspend count is greater than zero, the task is suspended.

In debug builds of embOS, upon calling OS_TASK_Suspend() more often than the maxi-

mum value without calling OS_TASK_Resume() the task’s internal suspend count is not in-

cremented and OS_Error() is called with error OS_ERR_SUSPEND_TOO_OFTEN.

Cannot be called from main(), an interrupt handler or software timer as this function may

cause an immediate task switch. The debug build of embOS will call the OS_Error() function

when OS_TASK_Suspend() is not called from a task.

Example

void HighPrioTask(void) {

OS_TASK_Suspend(NULL);

// Suspends itself, low priority task will be executed

}

void LowPrioTask(void) {

OS_TASK_Resume(&HighPrioTCB); // Resumes the high priority task

}

86 CHAPTER 2 API functions

2.4.30 OS_TASK_SuspendAll()

Description

Suspends all tasks except the running task.

Prototype

void OS_TASK_SuspendAll(void);

Additional information

This function may be used to inhibit task switches. It may be useful during application

initialization or supervising.

The calling task will not be suspended.

After calling OS_TASK_SuspendAll(), the calling task may block or suspend itself. No other

task will be activated unless one or more tasks are resumed again. The tasks may be re-

sumed individually by a call of OS_TASK_Resume() or all at once by a call of OS_TASK_Re-

sumeAll().

Example

Please refer to the example of OS_TASK_SetInitialSuspendCnt().

87 CHAPTER 2 API functions

2.4.31 OS_TASK_Terminate()

Description

Ends (terminates) a task.

Prototype

void OS_TASK_Terminate(OS_TASK* pTask);

Parameters

Parameter Description

pTask Pointer to the task control block structure of the task that

shall be terminated. A value of NULL terminates the current

task.

Additional information

The specified task will terminate immediately. The memory used for stack and task control

block can be reassigned.

All resources which are held by a task are released upon its termination. Any task may be

terminated regardless of its state.

Example

void Task(void) {

DoSomething();

OS_TASK_Terminate(NULL); // Terminate itself

}

88 CHAPTER 2 API functions

2.4.32 OS_TASK_Wake()

Description

Ends delay of a specified task immediately.

Prototype

void OS_TASK_Wake(OS_TASK* pTask);

Parameters

Parameter Description

pTask Pointer to a task control block structure.

Additional information

Places the specified task, which is already suspended for a certain amount of time by a call

of OS_TASK_Delay() or OS_TASK_DelayUntil(), back into the READY state.

The specified task will be activated immediately if it has a higher priority than the task that

had the highest priority before. If the specified task is not in the WAITING state (e.g. when

it has already been activated, or the delay has already expired, or for some other reason),

calling this function has no effect.

Example

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void HPTask(void) {

while (1) {

OS_TASK_Delay(50);

}

static void LPTask(void) {

while (1) {

OS_TASK_Delay(10);

OS_TASK_Wake(&TCBHP); // Wake HPTask which is in delay state

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

89 CHAPTER 2 API functions

2.4.33 OS_TASK_Yield()

Description

Calls the scheduler to force a task switch.

Prototype

void OS_TASK_Yield(void);

Additional information

If the task is running on round-robin, it will be suspended if there is another task with equal

priority ready for execution.

Example

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static void HPTask(void) {

while (1) {

DoSomething();

}

static void LPTask(void) {

while (1) {

DoSomethingElse();

// This task don't need the complete time slice.

// Give another task with the same priority the chance to run

OS_TASK_Yield();

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 100, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

Chapter 3

Software Timers

91 CHAPTER 3 Introduction

3.1 Introduction

A software timer is an object that calls a user-specified routine after a specified delay. An

unlimited number of software timers can be defined with the macro OS_TIMER_CREATE().

Timers can be stopped, started and retriggered much like hardware timers. When defining

a timer, you specify a routine to be called after the expiration of the delay. Timer routines

are similar to interrupt routines: they have a priority higher than the priority of any task.

For that reason they should be kept short just like interrupt routines.

Software timers are called by embOS with interrupts enabled, so they can be interrupted by

any hardware interrupt. Generally, timers run in single-shot mode, which means they expire

exactly once and call their callback routine exactly once. By calling OS_TIMER_Restart()

from within the callback routine, the timer is restarted with its initial delay time and there-

fore functions as a periodic timer.

The state of timers can be checked by the functions OS_TIMER_GetStatus(), OS_TIMER_Ge-

tRemainingPeriod() and OS_TIMER_GetPeriod().

Example

#include "RTOS.h"

#include "BSP.h"

static OS_TIMER TIMER50, TIMER200;

static void Timer50(void) {

BSP_ToggleLED(0);

OS_TIMER_Restart(&TIMER50);

}

static void Timer200(void) {

BSP_ToggleLED(1);

OS_TIMER_Restart(&TIMER200);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

BSP_Init(); // Initialize LED ports

OS_TIMER_CREATE(&TIMER50, Timer50, 50);

OS_TIMER_CREATE(&TIMER200, Timer200, 200);

OS_Start(); // Start embOS

return 0;

}

92 CHAPTER 3 Introduction

Minimum timeout / period

Software timer periods elapse with the appropriate embOS system tick. This means that the

actual timeout period can actually be slightly shorter than the configured timeout period.

For example, if the system tick is configured to occur once every msec, and the timer is

configured for a timeout of 1, the actual timeout duration is somewhere between 0 and

1 msec.

The following diagram illustrates how software timer timeouts work. We can see that the

timer configuration is performed prior to the first system tick, that is: at system time 0. The

timeout period is configured to 5 system ticks, therefore the callback is called upon the 5th

system tick. For example, if the the system ticks occurs at 1 msec, 2 msec, (…), 5 msec,

and the timer was started at 0.8 msec, the actual timer period would equal 4.2 msec.

Maximum timeout / period

The timeout value is stored as an integer, thus a 16 bit value on 8/16 bit CPUs, a 32 bit

value on 32 bit CPUs. The comparisons are done as signed comparisons because expired

time-outs are permitted. This means that only 15 bits can be used on 8/16 bit CPUs, 31

bits on 32 bit CPUs. Another factor to take into account is the maximum time spent in

critical regions. Timers may expire during critical regions, but because the timer routine

cannot be called from a critical region (timers are “put on hold”), the maximum time that

the system continuously spends in a critical region needs to be deducted. In most systems,

this is no more than a single tick. However, to be safe, we have assumed that your system

spends no more than a maximum of 255 consecutive system ticks in a critical region and

defined a macro for the maximum timeout value. This macro, OS_TIMER_MAX_TIME, defaults

to 0x7F00 on 8/16 bit systems and to 0x7FFFFF00 on 32 bit Systems as defined in RTOS.h.

If your system spends more than 255 consecutive ticks in a critical section, effectively

disabling the scheduler during this time (which is not recommended), you must ensure

your application uses shorter timeouts.

Extended software timers

Sometimes it may be useful to pass a parameter to the timer callback function. This allows

the callback function to be shared between different software timers. Since version 3.32m

of embOS, the extended timer structure and related extended timer functions were imple-

mented to allow parameter passing to the callback function.

Except for the different callback function with parameter passing, extended timers behave

exactly the same as regular embOS software timers and may be used in parallel with these.

93 CHAPTER 3 API functions

3.2 API functions

Routine Description

main

Task

ISR

Timer

OS_TIMER_CREATE() Macro that creates and starts a software

timer. ●●●●

OS_TIMER_Create() Creates a software timer without starting it. ● ● ● ●

OS_TIMER_CREATEEX() Macro that creates and starts an extended

software timer. ●●●●

OS_TIMER_CreateEx() Creates an extended software timer without

starting it. ●●●●

OS_TIMER_Delete() Stops and deletes a software timer. ● ● ● ●

OS_TIMER_DeleteEx() Stops and deletes an extended software

timer. ●●●●

OS_TIMER_GetCurrent() Returns a pointer to the data structure of the

timer that just expired. ●●●●

OS_TIMER_GetCurrentEx() Returns a pointer to the data structure of the

extended software timer that just expired. ●●●●

OS_TIMER_GetPeriod() Returns the current reload value of a soft-

ware timer. ●●●●

OS_TIMER_GetPeriodEx() Returns the current reload value of an ex-

tended software timer. ●●●●

OS_TIMER_GetRemaining-

Period() Returns the remaining timer value of a soft-

ware timer. ●●●●

OS_TIMER_GetRemaining-

PeriodEx() Returns the remaining timer value of an ex-

tended software timer. ●●●●

OS_TIMER_GetStatus() Returns the current timer status of a software

timer. ●●●●

OS_TIMER_GetStatusEx() Returns the current timer status of an ex-

tended software timer. ●●●●

OS_TIMER_Restart() Restarts a software timer with its initial time

value. ●●●●

OS_TIMER_RestartEx() Restarts an extended software timer with its

initial time value. ●●●●

OS_TIMER_SetPeriod() Sets a new timer reload value for a software

timer. ●●●●

OS_TIMER_SetPeriodEx() Sets a new timer reload value for an extend-

ed software timer. ●●●●

OS_TIMER_Start() Starts a software timer. ● ● ● ●

OS_TIMER_StartEx() Starts an extended software timer. ● ● ● ●

OS_TIMER_Stop() Stops a software timer. ● ● ● ●

OS_TIMER_StopEx() Stops an extended software timer. ● ● ● ●

OS_TIMER_Trigger() Ends a software timer at once and calls the

timer callback function. ● ●

OS_TIMER_TriggerEx() Ends an extended software timer at once and

calls the timer callback function. ● ●

94 CHAPTER 3 API functions

3.2.1 OS_TIMER_CREATE()

Description

Macro that creates and starts a software timer.

Prototype

void OS_TIMER_CREATE(OS_TIMER* pTimer,

OS_TIMERROUTINE* Callback,

OS_TIME Period);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the data of the

timer.

Callback Pointer to the callback routine to be called by the RTOS after expira-

tion of the delay. The callback function must be a void function which

does not take any parameters and does not return any value.

Period

Initial period in embOS system ticks.

The data type OS_TIME is defined as an integer, therefore valid values

are:

1 ≤ Period ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs

1 ≤ Period ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs

Additional information

embOS keeps track of the timers by using a linked list. Once the period is expired, the

callback routine will be called immediately (unless the current task is in a critical region

or has interrupts disabled).

This deprecated macro uses the functions OS_TIMER_Create() and OS_TIMER_Start(). It

is supplied for backward compatibility; in newer applications these routines should instead

be called directly.

OS_TIMERROUTINE is defined in RTOS.h as follows:

typedef void OS_TIMERROUTINE(void);

Source of the macro (in RTOS.h):

#define OS_TIMER_CREATE(pTimer, c, d) \

OS_TIMER_Create(pTimer, c, d); \

OS_TIMER_Start(pTimer);

Example

static OS_TIMER TIMER100;

static void Timer100(void) {

BSP_ToggleLED(0);

OS_TIMER_Restart(&TIMER100); // Make timer periodic

}

void InitTask(void) {

// Create and implicitly start Timer100

OS_TIMER_CREATE(&TIMER100, Timer100, 100);

}

95 CHAPTER 3 API functions

3.2.2 OS_TIMER_Create()

Description

Creates a software timer without starting it.

Prototype

void OS_TIMER_Create(OS_TIMER* pTimer,

OS_TIMERROUTINE* Callback,

OS_TIME Period);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Callback Pointer to the callback routine to be called by the RTOS after

expiration of the delay.

Period

Initial period in embOS system ticks.

The data type OS_TIME is defined as an integer, therefore

valid values are:

1 ≤ Period ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Period ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Additional information

embOS keeps track of the timers by using a linked list. Once the period is expired, the

callback routine will be called immediately (unless the current task is in a critical region or

has interrupts disabled). The timer is not automatically started. This must be done explicitly

by a call of OS_TIMER_Start() or OS_TIMER_Restart().

OS_TIMERROUTINE is defined in RTOS.h as follows:

typedef void OS_TIMERROUTINE(void);

Example

static OS_TIMER TIMER100;

static void Timer100(void) {

BSP_ToggleLED(0);

OS_TIMER_Restart(&TIMER100); // Make timer periodic

}

void InitTask(void) {

// Create Timer100, but start it seperately

OS_TIMER_Create(&TIMER100, Timer100, 100);

OS_TIMER_Start(&TIMER100);

}

96 CHAPTER 3 API functions

3.2.3 OS_TIMER_CREATEEX()

Description

Macro that creates and starts an extended software timer.

Prototype

void OS_TIMER_CREATEEX(OS_TIMER_EX* pTimerEx,

OS_TIMER_EX_ROUTINE* Callback,

OS_TIME Period,

void* pData);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended software timer.

Callback

Pointer to the callback routine to be called by the RTOS after

expiration of the delay. The callback function must be of type

OS_TIMER_EX_ROUTINE which takes a void pointer as parameter and

does not return any value.

Period

Initial period in embOS system ticks.

The data type OS_TIME is defined as an integer, therefore valid values

are:

1 ≤ Period ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs

1 ≤ Period ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs

pData A void pointer which is used as parameter for the extended timer call-

back function.

Additional information

embOS keeps track of the timers by using a linked list. Once the period is expired, the

callback routine will be called immediately (unless the current task is in a critical region

or has interrupts disabled).

This macro uses the functions OS_TIMER_CreateEx() and OS_TIMER_StartEx().

OS_TIMER_EX_ROUTINE is defined in RTOS.h as follows:

typedef void OS_TIMER_EX_ROUTINE(void *pVoid);

Source of the macro (in RTOS.h):

#define OS_TIMER_CREATEEX(pTimerEx, cb, Period, pData) \

OS_TIMER_CreateEx(pTimerEx, cb, Period, pData); \

OS_TIMER_StartEx(pTimerEx)

Example

static OS_TIMER_EX TIMER100;

static OS_TASK TCB_HP;

static void Timer100(void* pTask) {

if (pTask != NULL) {

OS_TASKEVENT_Set(0x01, (OS_TASK*)pTask);

}

OS_TIMER_RestartEx(&TIMER100); // Make timer periodic

}

void InitTask(void) {

97 CHAPTER 3 API functions

// Create and implicitly start Timer100

OS_TIMER_CREATEEX(&TIMER100, Timer100, 100, (void*)&TCB_HP);

}

98 CHAPTER 3 API functions

3.2.4 OS_TIMER_CreateEx()

Description

Creates an extended software timer without starting it.

Prototype

void OS_TIMER_CreateEx(OS_TIMER_EX* pTimerEx,

OS_TIMER_EX_ROUTINE* Callback,

OS_TIME Period,

void* pData);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains

the data of the extended software timer.

Callback Pointer to the callback routine of type OS_TIMER_EX_ROUTINE

to be called by the RTOS after expiration of the timer.

Period

Initial period in embOS system ticks.

The data type OS_TIME is defined as an integer, therefore

valid values are:

1 ≤ Period ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Period ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

pData A void pointer which is used as parameter for the extended

timer callback function.

Additional information

embOS keeps track of the timers by using a linked list. Once the period is expired, the

callback routine will be called immediately (unless the current task is in a critical region or

has interrupts disabled). The timer is not automatically started. This must be done explicitly

by a call of OS_TIMER_StartEx() or OS_TIMER_RestartEx().

OS_TIMER_EX_ROUTINE is defined in RTOS.h as follows:

typedef void OS_TIMER_EX_ROUTINE(void *pVoid);

Example

static OS_TIMER_EX TIMER100;

static OS_TASK TCB_HP;

static void Timer100(void* pTask) {

if (pTask != NULL) {

OS_TASKEVENT_Set(0x01, (OS_TASK*)pTask);

}

OS_TIMER_RestartEx(&TIMER100); // Make timer periodic

}

void InitTask(void) {

// Create Timer100, but start it seperately

OS_TIMER_CreateEx(&TIMER100, Timer100, 100, (void*)&TCB_HP);

OS_TIMER_Start(&TIMER100);

}

99 CHAPTER 3 API functions

3.2.5 OS_TIMER_Delete()

Description

Stops and deletes a software timer.

Prototype

void OS_TIMER_Delete(OS_TIMER* pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Additional information

The timer is stopped and therefore removed from the linked list of running timers. In debug

builds of embOS, the timer is also marked as invalid.

100 CHAPTER 3 API functions

3.2.6 OS_TIMER_DeleteEx()

Description

Stops and deletes an extended software timer.

Prototype

void OS_TIMER_DeleteEx(OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the timer.

Additional information

The extended software timer is stopped and removed from the linked list of running timers.

In debug builds of embOS, the timer is also marked as invalid.

101 CHAPTER 3 API functions

3.2.7 OS_TIMER_GetCurrent()

Description

Returns a pointer to the data structure of the software timer that just expired.

Prototype

OS_TIMER* OS_TIMER_GetCurrent(void);

Return value

A pointer to the control structure of a timer.

Additional information

The return value of OS_TIMER_GetCurrent() is valid during execution of a timer callback

function; otherwise it is undefined. If only one callback function should be used for multiple

timers, this function can be used for examining the timer that expired. The example below

shows one usage of OS_TIMER_GetCurrent(). Since version 3.32m of embOS, the extended

timer structure and functions may be used to generate and use a software timer with an

individual parameter for the callback function. Please be aware that OS_TIMER must be the

first member of the structure.

Example

#include "RTOS.h"

typedef struct {

OS_TIMER Timer; // OS_TIMER has to be the first element

void* pUser; // Any other data type may be used to extend the struct

} TIMER_EX;

static TIMER_EX Timer_User;

static int a;

static void _cb(void) {

TIMER_EX* p = (TIMER_EX*)OS_TIMER_GetCurrent();

void* pUser = p->pUser; // Examine user data

OS_TIMER_Restart(&p->Timer); // Make timer periodic

}

static void _CreateTimer(TIMER_EX* timer, OS_TIMERROUTINE* Callback,

OS_UINT Period, void* pUser) {

timer->pUser = pUser;

OS_TIMER_Create(&timer->Timer, Callback, Period);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

_CreateTimer(&Timer_User, _cb, 100, &a);

OS_Start(); // Start embOS

return 0;

}

102 CHAPTER 3 API functions

3.2.8 OS_TIMER_GetCurrentEx()

Description

Returns a pointer to the data structure of the extended software timer that just expired.

Prototype

OS_TIMER_EX* OS_TIMER_GetCurrentEx(void);

Return value

A pointer to the control structure of an extended software timer.

Additional information

The return value of OS_TIMER_GetCurrentEx() is valid during execution of a timer callback

function; otherwise it is undefined. If one callback function should be used for multiple

extended timers, this function can be used for examining the timer that expired.

Example

OS_TIMER_EX MyTimerEx;

static void _cbTimerEx(void* pData) {

OS_TIMER_EX* pTimerEx = OS_TIMER_GetCurrentEx();

OS_TASKEVENT_Set(0x01, (OS_TASK*)pData);

OS_TIMER_Restart(pTimerEx); // Make timer periodic

}

103 CHAPTER 3 API functions

3.2.9 OS_TIMER_GetPeriod()

Description

Returns the current reload value of a software timer.

Prototype

OS_TIME OS_TIMER_GetPeriod(OS_CONST_PTR OS_TIMER *pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Return value

Type OS_TIME, which is defined as an integer between

•1 and 215 - 1 = 0x7FFF for 8/16 bit CPUs and as an integer between

•1 and 231 - 1 = 0x7FFFFFFF for 32 bit CPUs, which is the permitted range of timer values.

Additional information

The period returned is the reload value of the timer which was set as initial value when the

timer was created or which was modified by a call of OS_TIMER_SetPeriod(). This reload

value will be used as time period when the timer is retriggered by OS_TIMER_Restart().

104 CHAPTER 3 API functions

3.2.10 OS_TIMER_GetPeriodEx()

Description

Returns the current reload value of an extended software timer.

Prototype

OS_TIME OS_TIMER_GetPeriodEx(OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended timer.

Return value

Type OS_TIME, which is defined as an integer between

•1 and 215 - 1 = 0x7FFF for 8/16 bit CPUs and as an integer between

•1 and 231 - 1 = 0x7FFFFFFF for 32 bit CPUs, which is the permitted range of timer values.

Additional information

The period returned is the reload value of the timer which was set as initial value when the

timer was created or which was modified by a call of OS_TIMER_SetPeriodEx(). This reload

value will be used as time period when the timer is retriggered by OS_TIMER_RestartEx().

105 CHAPTER 3 API functions

3.2.11 OS_TIMER_GetRemainingPeriod()

Description

Returns the remaining timer value of a software timer.

Prototype

OS_TIME OS_TIMER_GetRemainingPeriod(OS_CONST_PTR OS_TIMER *pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Return value

Type OS_TIME, which is defined as an integer between

•1 and 215 - 1 = 0x7FFF for 8/16 bit CPUs and as an integer between

•1 and 231 - 1 = 0x7FFFFFFF for 32 bit CPUs, which is the permitted range of timer values.

The returned timer value is the remaining timer time in embOS system ticks until expiration

of the timer.

106 CHAPTER 3 API functions

3.2.12 OS_TIMER_GetRemainingPeriodEx()

Description

Returns the remaining timer value of an extended software timer.

Prototype

OS_TIME OS_TIMER_GetRemainingPeriodEx(OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the timer.

Return value

Type OS_TIME, which is defined as an integer between

•1 and 215 - 1 = 0x7FFF for 8/16 bit CPUs and as an integer between

•1 and 231 - 1 = 0x7FFFFFFF for 32 bit CPUs, which is the permitted range of timer values.

The returned time value is the remaining timer value in embOS system ticks until expiration

of the extended software timer.

107 CHAPTER 3 API functions

3.2.13 OS_TIMER_GetStatus()

Description

Returns the current timer status of a software timer.

Prototype

OS_BOOL OS_TIMER_GetStatus(OS_CONST_PTR OS_TIMER *pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Return value

Denotes whether the specified timer is running or not:

= 0 Timer has stopped.

≠ 0 Timer is running.

108 CHAPTER 3 API functions

3.2.14 OS_TIMER_GetStatusEx()

Description

Returns the current timer status of an extended software timer.

Prototype

OS_BOOL OS_TIMER_GetStatusEx(OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended timer.

Return value

Denotes whether the specified timer is running or not:

= 0 Timer has stopped.

≠ 0 Timer is running.

109 CHAPTER 3 API functions

3.2.15 OS_TIMER_Restart()

Description

Restarts a software timer with its initial time value.

Prototype

void OS_TIMER_Restart(OS_TIMER* pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Additional information

OS_TIMER_Restart() restarts the timer using the initial time value programmed at creation

of the timer or with the function OS_TIMER_SetPeriod().

OS_TIMER_Restart() can be called regardless the state of the timer. A running timer will

continue using the full initial time. A timer that was stopped before or had expired will be

restarted.

Example

Please refer to the example for OS_TIMER_CREATE().

110 CHAPTER 3 API functions

3.2.16 OS_TIMER_RestartEx()

Description

Restarts an extended software timer with its initial time value.

Prototype

void OS_TIMER_RestartEx(OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended software timer.

Additional information

OS_TIMER_RestartEx() restarts the extended software timer using the initial time val-

ue which was programmed at creation of the timer or which was set using the function

OS_TIMER_SetPeriodEx().

OS_TIMER_RestartEx() can be called regardless of the state of the timer. A running timer

will continue using the full initial time. A timer that was stopped before or had expired will

be restarted.

Example

Please refer to the example for OS_TIMER_CREATEEX().

111 CHAPTER 3 API functions

3.2.17 OS_TIMER_SetPeriod()

Description

Sets a new timer reload value for a software timer.

Prototype

void OS_TIMER_SetPeriod(OS_TIMER* pTimer,

OS_TIME Period);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Period

Timer period in embOS system ticks.

The data type OS_TIME is defined as an integer, therefore

valid values are:

1 ≤ Period ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Period ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Additional information

OS_TIMER_SetPeriod() sets the initial time value of the specified timer. Period is the

reload value of the timer to be used as initial value when the timer is retriggered by

OS_TIMER_Restart().

Example

static OS_TIMER TIMERPulse;

static void TimerPulse(void) {

TogglePulseOutput(); // Toggle output

OS_TIMER_Restart(&TIMERPulse); // Make timer periodic

}

void InitTask(void) {

// Create and implicitly start timer with first pulse in 500 system ticks

OS_TIMER_CREATE(&TIMERPulse, TimerPulse, 500);

// Set timer period to 200 system ticks for further pulses

OS_TIMER_SetPeriod(&TIMERPulse, 200);

}

112 CHAPTER 3 API functions

3.2.18 OS_TIMER_SetPeriodEx()

Description

Sets a new timer reload value for an extended software timer.

Prototype

void OS_TIMER_SetPeriodEx(OS_TIMER_EX* pTimerEx,

OS_TIME Period);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended software timer.

Period

Initial period in embOS system ticks.

The data type OS_TIME is defined as an integer, therefore valid values

are:

1 ≤ Period ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs

1 ≤ Period ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs

Additional information

OS_TIMER_SetPeriodEx() sets the initial time value of the specified extended software

timer. Period is the reload value of the timer to be used as initial value when the timer is

retriggered the next time by OS_TIMER_RestartEx().

A call of OS_TIMER_SetPeriodEx() does not affect the remaining time period of an extended

software timer.

Example

static OS_TIMER_EX TIMERPulse;

static OS_TASK TCB_HP;

static void TimerPulse(void* pTask) {

if (pTask != NULL) {

OS_TASKEVENT_Set(0x01, (OS_TASK*)pTask);

}

OS_TIMER_RestartEx(&TIMERPulse); // Make timer periodic

}

void InitTask(void) {

// Create and implicitly start Pulse Timer with first pulse in 500 system ticks

OS_TIMER_CREATEEX(&TIMERPulse, TimerPulse, 500, (void*)&TCB_HP);

// Set timer period to 200 system ticks for further pulses

OS_TIMER_SetPeriodEx(&TIMERPulse, 200);

}

113 CHAPTER 3 API functions

3.2.19 OS_TIMER_Start()

Description

Starts a software timer.

Prototype

void OS_TIMER_Start(OS_TIMER* pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Additional information

OS_TIMER_Start() is used for the following reasons:

• Start a timer which was created by OS_TIMER_Create(). The timer will start with its

initial timer value.

• Restart a timer which was stopped by calling OS_TIMER_Stop(). In this case, the timer

will continue with the remaining time value which was preserved upon stopping the

timer.

Note

This function has no effect on running timers. It also has no effect on timers that are

not running, but have expired: use OS_TIMER_Restart() to restart those timers.

114 CHAPTER 3 API functions

3.2.20 OS_TIMER_StartEx()

Description

Starts an extended software timer.

Prototype

void OS_TIMER_StartEx(OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended software timer.

Additional information

OS_TIMER_StartEx() is used for the following reasons:

• Start an extended software timer which was created by OS_TIMER_CreateEx(). The

timer will start with its initial timer value.

• Restart a timer which was stopped by calling OS_TIMER_StopEx(). In this case, the

timer will continue with the remaining time value which was preserved upon stopping

the timer.

Note

This function has no effect on running timers. It also has no effect on timers that are

not running, but have expired. Use OS_TIMER_RestartEx() to restart those timers.

115 CHAPTER 3 API functions

3.2.21 OS_TIMER_Stop()

Description

Stops a software timer.

Prototype

void OS_TIMER_Stop(OS_TIMER* pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Additional information

The actual value of the timer (the time until expiration) is maintained until OS_TIMER_S-

tart() lets the timer continue. The function has no effect on timers that are not running,

but have expired.

116 CHAPTER 3 API functions

3.2.22 OS_TIMER_StopEx()

Description

Stops an extended software timer.

Prototype

void OS_TIMER_StopEx(OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended software timer.

Additional information

The actual time value of the extended software timer (the time until expiration) is main-

tained until OS_TIMER_StartEx() lets the timer continue. The function has no effect on

timers that are not running, but have expired.

117 CHAPTER 3 API functions

3.2.23 OS_TIMER_Trigger()

Description

Ends a software timer at once and calls the timer callback function.

Prototype

void OS_TIMER_Trigger(OS_TIMER* pTimer);

Parameters

Parameter Description

pTimer Pointer to the OS_TIMER data structure which contains the

data of the timer.

Additional information

OS_TIMER_Trigger() can be called regardless of the state of the timer. A running timer will

be stopped and the callback function is called. For a timer that was stopped before or had

expired the callback function will not be executed.

Example

static OS_TIMER TIMERUartRx;

void TimerUart(void) {

HandleUartRx();

}

void UartRxIntHandler(void) {

OS_TIMER_Trigger(&TIMERUartRx); // Character received, stop the software timer

}

void UartSendNextCharachter(void) {

OS_TIMER_Start(&TIMERUartRx);

// Send next uart character and wait for Rx character

}

int main(void) {

OS_TIMER_Create(&TIMERUartRx, TimerUart, 20);

}

118 CHAPTER 3 API functions

3.2.24 OS_TIMER_TriggerEx()

Description

Ends an extended software timer at once and calls the timer callback function.

Prototype

void OS_TIMER_TriggerEx (OS_TIMER_EX* pTimerEx);

Parameters

Parameter Description

pTimerEx Pointer to the OS_TIMER_EX data structure which contains the data of

the extended software timer.

Additional information

OS_TIMER_TriggerEx() can be called regardless of the state of the timer. A running timer

will be stopped and the callback function is called. For a timer that was stopped before or

had expired the callback function will not be executed.

Example

static OS_TIMER_EX TIMERUartRx;

static OS_U32 UartNum;

void TimerUart(void* pNum) {

HandleUartRx((OS_U32)pNum);

}

void UartRxIntHandler(void) {

OS_TIMER_TriggerEx(&TIMERUartRx);

// Character received, stop the software timer

}

void UartSendNextCharachter(void) {

OS_TIMER_StartEx(&TIMERUartRx);

// Send next uart character and wait for Rx character

}

int main(void) {

UartNum = 0;

OS_TIMER_CreateEx(&TIMERUartRx, TimerUart, 20, (void*)&UartNum);

}

Chapter 4

Task Events

120 CHAPTER 4 Introduction

4.1 Introduction

Task events are another way of communicating between tasks. In contrast to semaphores

and mailboxes, task events are messages to a single, specified recipient. In other words,

a task event is sent to a specified task.

The purpose of a task event is to enable a task to wait for a particular event (or for one

of several events) to occur. This task can be kept inactive until the event is signaled by

another task, a software timer or an interrupt handler. An event can be, for example, the

change of an input signal, the expiration of a timer, a key press, the reception of a character,

or a complete command.

Every task has an individual bit mask, which by default is the width of an unsigned integer,

usually the word size of the target processor. This means that 32 or 8 different events can

be signaled to and distinguished by every task. By calling OS_TASKEVENT_GetBlocked(), a

task waits for one of the events specified as a bitmask. As soon as one of the events occurs,

this task must be signaled by calling OS_TASKEVENT_Set(). The waiting task will then be put

in the READY state immediately. It will be activated according to the rules of the scheduler

as soon as it becomes the task with the highest priority of all tasks in the READY state.

By changing the definition of OS_TASKEVENT, which is defined as unsigned long on 32 bit

CPUs and unsigned char on 16 or 8 bit CPUs per default, the task events can be expanded

to 16 or 32 bits thus allowing more individual events, or reduced to smaller data types

on 32 bit CPUs.

Changing the definition of OS_TASKEVENT can only be done when using the embOS sources

in a project, or when the libraries are rebuilt from sources with the modified definition.

Example

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static OS_TASKEVENT MyEvents;

static void HPTask(void) {

while (1) {

MyEvents = OS_TASKEVENT_GetBlocked(3); // Wait for event bits 0 or 1

if (MyEvents & 1) {

_HandleEvent0();

} else

_HandleEvent1();

}

static void LPTask(void) {

while (1) {

OS_TASK_Delay(200);

OS_TASKEVENT_Set(&TCBHP, 1);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start embOS

return 0;

}

121 CHAPTER 4 API functions

4.2 API functions

Routine Description

main

Task

ISR

Timer

OS_TASKEVENT_Clear() Returns the actual state of events and then

clears all events of a specified task. ●●●●

OS_TASKEVENT_ClearEx() Returns the actual state of events and then

clears the specified events for the specified

task.

●●●●

OS_TASKEVENT_Get() Returns a list of events that have occurred

for a specified task. ● ●

OS_TASKEVENT_GetBlocked() Waits for one of the events specified in the

bitmask and clears the event memory when

the function returns.

●

OS_TASKEVENT_GetSingle-

Blocked()

Waits for one of the specified events and

clears only those events that were specified

in the event mask.

●

OS_TASKEVENT_GetSingle-

Timed()

Waits for one of the specified events for

a given time and clears only those events

that were specified in the event mask.

●

OS_TASKEVENT_GetTimed() Waits for the specified events for a given

time, and clears the event memory when

the function returns.

●

OS_TASKEVENT_Set() Signals event(s) to a specified task. ● ● ● ●

122 CHAPTER 4 API functions

4.2.1 OS_TASKEVENT_Clear()

Description

Returns the actual state of events and then clears all events of a specified task.

Prototype

OS_TASKEVENT OS_TASKEVENT_Clear(OS_TASK* pTask);

Parameters

Parameter Description

pTask The task whose event mask is to be returned, NULL means

current task.

Return value

All events that have been signaled before clearing. If pTask is NULL, the function clears all

events of the currently running task.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task.

Example

void Task(void) {

OS_TASKEVENT MyEvents;

MyEvents = OS_TASKEVENT_Clear(NULL);

while (1) {

// Wait for event 0 or 1 to be signaled

MyEvents = OS_TASKEVENT_GetBlocked(3);

}

123 CHAPTER 4 API functions

4.2.2 OS_TASKEVENT_ClearEx()

Description

Returns the actual state of events and then clears the specified events for the specified task.

Prototype

OS_TASKEVENT OS_TASKEVENT_ClearEx(OS_TASK* pTask,

OS_TASKEVENT EventMask);

Parameters

Parameter Description

pTask The task whose event mask is to be returned, NULL means

current task.

EventMask The bit mask containing the event bits which shall be

cleared.

Return value

All events that have been signaled before clearing. If pTask is NULL, the function clears the

events of the currently running task.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task.

Example

void Task(void) {

OS_TASKEVENT MyEvents;

MyEvents = OS_TASKEVENT_ClearEx(NULL, 1);

while (1) {

// Wait for event 0 or 1 to be signaled

MyEvents = OS_TASKEVENT_GetBlocked(3);

}

124 CHAPTER 4 API functions

4.2.3 OS_TASKEVENT_Get()

Description

Returns a list of events that have occurred for a specified task.

Prototype

OS_TASKEVENT OS_TASKEVENT_Get(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask The task whose event mask is to be returned, NULL means

current task.

Return value

All events that have been signaled.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task.

By calling this function, all events remain signaled: event memory is not cleared. This is one

way for a task to query which events are signaled. The task is not suspended if no events

are signaled. If pTask is NULL, the function clears the events of the currently running task.

void PrintEvents(void) {

OS_TASKEVENT MyEvents;

MyEvents = OS_TASKEVENT_Get(NULL);

printf("Events %u\n", MyEvents);

}

125 CHAPTER 4 API functions

4.2.4 OS_TASKEVENT_GetBlocked()

Description

Waits for one of the events specified in the bitmask and clears the event memory when

the function returns.

Prototype

OS_TASKEVENT OS_TASKEVENT_GetBlocked(OS_TASKEVENT EventMask);

Parameters

Parameter Description

EventMask The event bit mask containing the event bits, which shall be

waited for.

Return value

All events that have been signaled.

Additional information

If none of the specified events are signaled, the task is suspended. The first of the specified

events will wake the task. These events are signaled by another task, a software timer or

an interrupt handler. Any bit that is set in the event mask enables the corresponding event.

When a task waits on multiple events, all of the specified events shall be requested by a

single call of OS_TASKEVENT_GetBlocked() and all events must be be handled when the

function returns.

Note that all events of the task are cleared when the function returns, even those events

that were not set in the parameters in the eventmask. Consecutive calls of OS_TASKEVEN-

T_GetBlocked() with different event masks will not work, as all events are cleared when

the function returns. Events may be lost. OS_TASKEVENT_GetSingleBlocked() may be used

for this case.

Example

void Task(void) {

OS_TASKEVENT MyEvents;

while(1) {

MyEvents = OS_TASKEVENT_GetBlocked(3); // Wait for event 0 or

1 to be signaled

// Handle ALL events

if (MyEvents & (1 << 0)) {

_HandleEvent0();

}

if (MyEvents & (1 << 1)) {

_HandleEvent1();

}

For another example, see OS_TASKEVENT_Set().

126 CHAPTER 4 API functions

4.2.5 OS_TASKEVENT_GetSingleBlocked()

Description

Waits for one of the specified events and clears only those events that were specified in

the event mask.

Prototype

OS_TASKEVENT OS_TASKEVENT_GetSingleBlocked(OS_TASKEVENT EventMask);

Parameters

Parameter Description

EventMask The event bit mask containing the event bits, which shall be

waited for and reset.

Return value

All requested events that have been signaled and were specified in the EventMask.

Additional information

If none of the specified events are signaled, the task is suspended. The first of the requested

events will wake the task. These events are signaled by another task, a software timer, or an

interrupt handler. Any bit in the event mask may enable the corresponding event. When the

function returns, it delivers all of the requested events. The requested events are cleared

in the event state of the task. All other events remain unchanged and will not be returned.

OS_TASKEVENT_GetSingleBlocked() may be used in consecutive calls with individual re-

quests. Only requested events will be handled, no other events can get lost. When the

function waits on multiple events, the returned value must be evaluated because the func-

tion returns when at least one of the requested events was signaled. When the function

requests a single event, the returned value does not need to be evaluated.

Example

void Task(void) {

OS_TASKEVENT MyEvents;

while(1) {

MyEvents = OS_TASKEVENT_GetSingleBlocked(3); // Wait for event 0 or

1 to be signaled

// Handle ALL events

if (MyEvents & (1 << 0)) {

_HandleEvent0();

}

if (MyEvents & (1 << 1)) {

_HandleEvent1();

}

OS_TASKEVENT_GetSingleBlocked(1 << 2); // Wait for event

2 to be signaled

_HandleEvent2();

OS_TASKEVENT_GetSingleBlocked(1 << 3); // Wait for event

3 to be signaled

_HandleEvent3();

}

127 CHAPTER 4 API functions

4.2.6 OS_TASKEVENT_GetSingleTimed()

Description

Waits for one of the specified events for a given time and clears only those events that

were specified in the event mask.

Prototype

OS_TASKEVENT OS_TASKEVENT_GetSingleTimed(OS_TASKEVENT EventMask,

OS_TIME TimeOut);

Parameters

Parameter Description

EventMask The event bit mask containing the event bits, which shall be

waited for and reset.

TimeOut

Maximum time in embOS system ticks until the events must

be signaled. The data type OS_TIME is defined as an integer,

therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

All requested events that have been signaled and were specified in the EventMask.

Additional information

If none of the specified events are available, the task is suspended for the given time. The

first of the specified events will wake the task if the event is signaled by another task, a

software timer or an interrupt handler within the specified TimeOut time.

If no event is signaled, the task is activated after the specified timeout and the function

returns zero. Any bit in the event mask may enable the corresponding event. All unmasked

events remain unchanged.

Example

void Task(void) {

OS_TASKEVENT MyEvents;

while(1) {

MyEvents = OS_TASKEVENT_GetSingleTimed(3, 10); // Wait for event 0 or

1 to be

// signaled within 10ms

/* Handle requested events */

if (MyEvents == 0) {

_HandleTimeout;

} else {

if (MyEvents & (1 << 0)) {

_HandleEvent0();

}

if (MyEvents & (1 << 1)) {

_HandleEvent1();

}

if (OS_TASKEVENT_GetSingleBlocked((1 << 2), 10) == 0) {

_HandleTimeout();

} else {

_HandleEvent2();

}

128 CHAPTER 4 API functions

4.2.7 OS_TASKEVENT_GetTimed()

Description

Waits for the specified events for a given time, and clears the event memory when the

function returns.

Prototype

OS_TASKEVENT OS_TASKEVENT_GetTimed(OS_TASKEVENT EventMask,

OS_TIME TimeOut);

Parameters

Parameter Description

EventMask The event bit mask containing the event bits, which shall be

waited for.

TimeOut

Maximum time in embOS system ticks waiting for events to

be signaled. The data type OS_TIME is defined as an integer,

therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

All events that have been signaled.

Additional information

If none of the specified events are available, the task is suspended for the given time. The

first of the requested events will wake the task if the event is signaled by another task, a

software timer, or an interrupt handler within the specified TimeOut time.

If none of the requested events is signaled, the task is activated after the specified timeout

and all signaled events are returned and then cleared. Note that the function returns all

events that were signaled within the given timeout time, even those which were not request-

ed. The calling function must handle the returned value. Consecutive calls of OS_TASKEVEN-

T_GetTimed() with different event masks will not work, as all events are cleared when the

function returns. Events may got lost. OS_TASKEVENT_GetSingleTimed() may be used for

this case.

Example

void Task(void) {

OS_TASKEVENT MyEvents;

while(1) {

MyEvents = OS_TASKEVENT_GetTimed(3, 10); // Wait for events 0+1 for 10 msec

if ((MyEvents & 0x3) == 0) {

_HandleTimeout();

} else {

if (MyEvents & (1 << 0)) {

_HandleEvent0();

}

if (MyEvents & (1 << 1)) {

_HandleEvent1();

}

129 CHAPTER 4 API functions

4.2.8 OS_TASKEVENT_Set()

Description

Signals event(s) to a specified task.

Prototype

void OS_TASKEVENT_Set(OS_TASK* pTask,

OS_TASKEVENT Event);

Parameters

Parameter Description

pTask Pointer to the task control block.

Event The event bit mask containing the event bits, which shall be

signaled.

Additional information

If the specified task is waiting for one of these events, it will be put in the READY state and

activated according to the rules of the scheduler.

Example

The task that handles the serial input and the keyboard waits for a character to be received

either via the keyboard (EVENT_KEYPRESSED) or serial interface (EVENT_SERIN):

#define EVENT_KEYPRESSED (1u << 0)

#define EVENT_SERIN (1u << 1)

static OS_STACKPTR int Stack0[96]; // Task stacks

static OS_TASK TCB0; // Data area for tasks (task control blocks)

void Task0(void) {

OS_TASKEVENT MyEvent;

while(1)

MyEvent = OS_TASKEVENT_GetBlocked(EVENT_KEYPRESSED | EVENT_SERIN)

if (MyEvent & EVENT_KEYPRESSED) {

// Handle key press

}

if (MyEvent & EVENT_SERIN) {

// Handle serial reception

}

void Key_ISR(void) { // ISR for external interrupt

OS_TASKEVENT_Set(&TCB0, EVENT_KEYPRESSED); // Notify task that key was pressed

}

void UART_ISR(void) { // ISR for uart interrupt

OS_TASKEVENT_Set(&TCB0, EVENT_SERIN);

// Notify task that a character was received

}

void InitTask(void) {

OS_TASK_CREATE(&TCB0, "HPTask", 100, Task0, Stack0);

}

If the task was only waiting for a key to be pressed, OS_MAILBOX_GetBlocked() could

simply be called. The task would then be deactivated until a key is pressed.

Chapter 5

Event Objects

131 CHAPTER 5 Introduction

5.1 Introduction

Event objects are another type of communication and synchronization object. In contrast

to task-events, event objects are standalone objects which are not owned by any task.

The purpose of an event object is to enable one or multiple tasks to wait for a particular

event to occur. The tasks can be kept suspended until the event is set by another task,

a software timer, or an interrupt handler. An event can be, for example, the change of

an input signal, the expiration of a timer, a key press, the reception of a character, or a

complete command.

Compared to a task event, the signaling function does not need to know which task is

waiting for the event to occur.

Reset mode

Since version 3.88a of embOS, the reset behavior of the event can be controlled by different

reset modes which may be passed as parameter to the new function OS_EVENT_CreateEx()

or may be modified by a call of OS_EVENT_SetResetMode().

•OS_EVENT_RESET_MODE_SEMIAUTO:

This reset mode is the default mode used with all previous versions of embOS. The

reset behavior unfortunately is not consistent and depends on the function called to

set or wait for an event. This reset mode is defined for compatibility with older embOS

versions (prior version 3.88a). Calling OS_EVENT_Create() sets the reset mode to

OS_EVENT_RESET_MODE_SEMIAUTO to be compatible with older embOS versions.

•OS_EVENT_RESET_MODE_AUTO:

This mode sets the reset behavior of an event object to automatic clear. When an event

is set, all waiting tasks are resumed and the event is cleared automatically. An exception

to this is when a task called OS_EVENT_GetTimed() and the timeout expired before the

event was signaled, in which case the function returns with timeout and the event is

not cleared automatically.

•OS_EVENT_RESET_MODE_MANUAL:

This mode sets the event to manual reset mode. When an event is set, all waiting tasks

are resumed and the event object remains signaled. The event must be reset by one

task which was waiting for the event.

Mask mode

Since version 4.34 of embOS, the mask bits behavior of the event object can be controlled

by different mask modes which may be passed to the new function OS_EVENT_CreateEx()

or may be modified by a call of OS_EVENT_SetMaskMode().

•OS_EVENT_MASK_MODE_OR_LOGIC:

This mask mode is the default mode. Only one of the bits specified in the event object

bit mask must be signaled.

•OS_EVENT_MASK_MODE_AND_LOGIC:

With this mode all specified event object mask bits must be signaled.

132 CHAPTER 5 Introduction

5.1.1 Examples of using event objects

This section shows some examples on how to use event objects in an application.

5.1.1.1 Activate a task from interrupt by an event object

The following code example shows usage of an event object which is signaled from an ISR

handler to activate a task. The waiting task should reset the event after waiting for it.

static OS_EVENT _Event;

static void _ISRHandler(void) {

OS_INT_Enter();

// Wake up task to do the rest of the work

OS_EVENT_Set(&_Event);

OS_INT_LEAVE();

}

static void Task(void) {

while (1) {

OS_EVENT_GetBlocked(&_Event);

// Do the rest of the work (which has not been done in the ISR)

...

}

5.1.1.2 Activating multiple tasks using a single event object

The following sample program shows how to synchronize multiple tasks with one event

object. The sample program is delivered with embOS in the “Application” folder.

#include "RTOS.h"

/*********************************************************************

* Static data

**********************************************************************

static OS_STACKPTR int StackHP[128], StackLP[128], StackHW[128];

static OS_TASK TCBHP, TCBLP, TCBHW;

static OS_EVENT HW_Event;

/*********************************************************************

* HPTask()

static void HPTask(void) {

// Wait until HW module is set up

OS_EVENT_GetBlocked(&HW_Event);

while (1) {

OS_TASK_Delay(50);

}

/*********************************************************************

* LPTask()

133 CHAPTER 5 Introduction

static void LPTask(void) {

// Wait until HW module is set up

OS_EVENT_GetBlocked(&HW_Event);

while (1) {

OS_TASK_Delay(200);

}

/*********************************************************************

* HWTask()

static void HWTask(void) {

// Wait until HW module is set up

OS_TASK_Delay(100);

// Init done, send broadcast to waiting tasks

OS_EVENT_Set(&HW_Event);

while (1) {

OS_TASK_Delay(40);

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_TASK_CREATE(&TCBHW, "HWTask", 25, HWTask, StackHW);

OS_EVENT_Create(&HW_Event);

OS_Start(); // Start multitasking

return 0;

}

134 CHAPTER 5 API functions

5.2 API functions

Routine Description

main

Task

ISR

Timer

OS_EVENT_Create() Creates an event object and resets the

event. ●●●●

OS_EVENT_CreateEx() Creates an extended event object and sets

its reset behavior as well as mask bits be-

havior.

●●●●

OS_EVENT_Delete() Deletes an event object and releases all

waiting tasks. ● ●

OS_EVENT_Get() Retrieves current state of an event object

without modification or suspension. ●●●●

OS_EVENT_GetBlocked() Waits for an event object and suspends

task if event is not signaled. ●

OS_EVENT_GetMask() Returns the bits of an event object that

match the given EventMask.● ●

OS_EVENT_GetMaskBlocked() Waits for the specified event bits, depend-

ing on the current mask mode. ●

OS_EVENT_GetMaskMode() Retrieves the current mask mode (mask

bits behavior) of an event object. ●●●●

OS_EVENT_GetMaskTimed() Waits for the specified event bits with time-

out, depending on the current mask mode. ●

OS_EVENT_GetResetMode() Returns the reset mode (reset behavior) of

an event object. ●●●●

OS_EVENT_GetTimed() Waits for an event and suspends the task

for a specified time or until the event has

been signaled.

●

OS_EVENT_Pulse() Signals an event object and resumes wait-

ing tasks, then resets the event object to

non-signaled state.

●●●●

OS_EVENT_Reset() Resets the specified event object to non-

signaled state. ●●●●

OS_EVENT_Set() Sets an event object to signaled state, or

resumes tasks which are waiting at the

event object.

●●●●

OS_EVENT_SetMask() Sets the event mask bits of an event ob-

ject. ●●●●

OS_EVENT_SetMaskMode() Sets the mask mode of an event object to

OR/AND logic. ●●●●

OS_EVENT_SetResetMode() Sets the reset behavior of an event object

to auto-matic, manual or semiauto. ●●●●

135 CHAPTER 5 API functions

5.2.1 OS_EVENT_Create()

Description

Creates an event object and resets the event. Must be called before the event object can

be used.

Prototype

void OS_EVENT_Create(OS_EVENT* pEvent);

Parameters

Parameter Description

pEvent Pointer to an event object data structure.

Additional information

Before the event object can be used, it must be created by a call of OS_EVENT_Create().

On creation, the event is set in non-signaled state, and the list of waiting tasks is empty.

Therefore, OS_EVENT_Create() must not be called for an event object which is already

created.

A debug build of embOS cannot check whether the specified event object was already

created.

The event is created with the default reset behavior which is semiauto. Since version 3.88a

of embOS, the reset behavior of the event can be modified by a call of the function OS_EVEN-

T_SetResetMode().

Example

static OS_EVENT _Event;

void HPTask(void) {

OS_EVENT_GetMaskBlocked(&_Event, 3); // Wait for bit 0 AND 1 to be set

}

void LPTask(void) {

OS_EVENT_SetMask(&_Event, 1); // Resumes HPTask due to OR logic

}

int main(void) {

...

OS_EVENT_Create(&_Event);

...

return 0;

}

136 CHAPTER 5 API functions

5.2.2 OS_EVENT_CreateEx()

Description

Creates an extended event object and sets its reset behavior as well as mask bits behavior.

Prototype

void OS_EVENT_CreateEx(OS_EVENT* pEvent,

unsigned int Mode);

Parameters

Parameter Description

pEvent Pointer to an event object data structure.

Mode

Specifies the reset and mask bits behavior of the event ob-

ject. You can use one of the predefined reset modes:

OS_EVENT_RESET_MODE_SEMIAUTO

OS_EVENT_RESET_MODE_MANUAL

OS_EVENT_RESET_MODE_AUTO

and one of the mask modes:

OS_EVENT_MASK_MODE_OR_LOGIC

OS_EVENT_MASK_MODE_AND_LOGIC

which are described under additional information.

Additional information

Before the event object can be used, it must be created by a call of OS_EVENT_Create() or

OS_EVENT_CreateEx(). On creation, the event is set in nonsignaled state, and the list of

waiting tasks is empty. Therefore, OS_EVENT_CreateEx() must not be called for an event

object which is already created. A debug build of embOS cannot check whether the specified

event object was already created.

Since version 3.88a of embOS, the reset behavior of the event can be controlled by different

reset modes which may be passed as parameter to the new function OS_EVENT_CreateEx()

or may be modified by a call of OS_EVENT_SetResetMode().

•OS_EVENT_RESET_MODE_SEMIAUTO:

This reset mode is the default mode used with all previous versions of embOS. The

reset behavior unfortunately is not consistent and depends on the function called to

set or wait for an event. This reset mode is defined for compatibility with older embOS

versions (prior version 3.88a). Calling OS_EVENT_Create() sets the reset mode to

OS_EVENT_RESET_MODE_SEMIAUTO to be compatible with older embOS versions.

•OS_EVENT_RESET_MODE_AUTO:

This mode sets the reset behavior of an event object to automatic clear. When an event

is set, all waiting tasks are resumed and the event is cleared automatically. An exception

to this is when a task called OS_EVENT_GetTimed() and the timeout expired before the

event was signaled, in which case the function returns with timeout and the event is

not cleared automatically.

•OS_EVENT_RESET_MODE_MANUAL:

This mode sets the event to manual reset mode. When an event is set, all waiting tasks

are resumed and the event object remains signaled. The event must be reset by one

task which was waiting for the event.

Since version 4.34 of embOS, the mask bits behavior of the event object can be controlled

by different mask modes which may be passed to the new function OS_EVENT_CreateEx()

or may be modified by a call of OS_EVENT_SetMaskMode().

•OS_EVENT_MASK_MODE_OR_LOGIC:

This mask mode is the default mode. Only one of the bits specified in the event object

bit mask must be signaled.

•OS_EVENT_MASK_MODE_AND_LOGIC:

With this mode all specified event object mask bits must be signaled.

137 CHAPTER 5 API functions

Example

static OS_EVENT _Event;

void HPTask(void) {

OS_EVENT_GetMaskBlocked(&_Event, 3); // Wait for bit 0 AND 1 to be set

}

void LPTask(void) {

OS_EVENT_SetMask(&_Event, 1); // Does not resume HPTask

OS_EVENT_SetMask(&_Event, 2);

// Resume HPTask since both bits are now set

}

int main(void) {

...

OS_EVENT_CreateEx(&_Event, OS_EVENT_RESET_MODE_AUTO |

OS_EVENT_MASK_MODE_AND_LOGIC);

...

return 0;

}

138 CHAPTER 5 API functions

5.2.3 OS_EVENT_Delete()

Description

Deletes an event object and releases all waiting tasks.

Prototype

void OS_EVENT_Delete(OS_EVENT* pEvent);

Parameters

Parameter Description

pEvent Pointer to an event object which should be deleted.

Additional information

To keep the system fully dynamic, it is essential that event objects can be created dynam-

ically. This also means there must be a way to delete an event object when it is no longer

needed. The memory that has been used by the event object’s control structure can then

be reused or reallocated.

It is your responsibility to make sure that:

• the program no longer uses the event object to be deleted

• the event object to be deleted actually exists (has been created first)

• no tasks are waiting at the event object when it is deleted.

pEvent must address an existing event object, which has been created before by a call of

OS_EVENT_Create() or OS_EVENT_CreateEx(). A debug build of embOS will check whether

pEvent addresses a valid event object and will call OS_Error() with error code OS_ER-

R_EVENT_INVALID in case of an error. If any task is waiting at the event object which is

deleted, a debug build of embOS calls OS_Error() with error code OS_ERR_EVENT_DELETE.

To avoid any problems, an event object should not be deleted in a normal application.

Example

static OS_EVENT _Event;

void Task(void) {

...

OS_EVENT_Delete(&_Event);

...

}

139 CHAPTER 5 API functions

5.2.4 OS_EVENT_Get()

Description

Retrieves current state of an event object without modification or suspension.

Prototype

OS_BOOL OS_EVENT_Get(OS_CONST_PTR OS_EVENT *pEvent);

Parameters

Parameter Description

pEvent Pointer to an event object whose state should be examined.

Return value

0 Event object is not set to signaled state.

1 Event object is set to signaled state.

Additional information

By calling this function, the actual state of the event object remains unchanged. pEvent

must address an existing event object, which has been created before by a call of OS_EVEN-

T_Create().

A debug build of embOS will check whether pEvent addresses a valid event object and will

call OS_Error() with error code OS_ERR_EVENT_INVALID in case of an error.

Example

static OS_EVENT _Event;

void Task(void) {

OS_BOOL Status;

Status = OS_EVENT_Get(&_Event);

printf("Event Object Status: %d\n", Status);

}

140 CHAPTER 5 API functions

5.2.5 OS_EVENT_GetBlocked()

Description

Waits for an event object and suspends task if event is not signaled.

Prototype

void OS_EVENT_GetBlocked(OS_EVENT* pEvent);

Parameters

Parameter Description

pEvent Pointer to the event object that the task will be waiting for.

Additional information

pEvent addresses an existing event object, which must be created before the call of

OS_EVENT_GetBlocked(). A debug build of embOS will check whether pEvent addresses

a valid event object and will call OS_Error() with error code OS_ERR_EVENT_INVALID in

case of an error.

The state of the event object after calling OS_EVENT_GetBlocked() depends on the reset

mode of the event object which was set by creating the event object by a call of OS_EVEN-

T_CreateEx() or OS_EVENT_SetResetMode().

The event is consumed when OS_EVENT_RESET_MODE_AUTO is selected. The event is not

consumed when OS_EVENT_RESET_MODE_MANUAL is selected. With OS_EVENT_RESET_MOD-

E_SEMIAUTO the event is consumed only when it was already set before.

Example

static OS_EVENT _Event;

void HPTask(void) {

OS_EVENT_GetBlocked(&_Event); // Suspends the task

}

void LPTask(void) {

OS_EVENT_Pulse(&_Event); // Signals the HPTask

}

141 CHAPTER 5 API functions

5.2.6 OS_EVENT_GetMask()

Description

Returns the bits of an event object that match the given EventMask.

Prototype

OS_TASKEVENT OS_EVENT_GetMask(OS_EVENT* pEvent,

OS_TASKEVENT EventMask);

Parameters

Parameter Description

pEvent Pointer to an event object whose state should be examined.

EventMask The bit mask containing the event bits which shall be re-

trieved.

Return value

Matching event object mask bits.

Additional information

The signaled event mask bits are consumed unless OS_EVENT_RESET_MODE_MANUAL is se-

lected. pEvent must address an existing event object, which has been created before by

a call of OS_EVENT_Create().

A debug build of embOS will check whether pEvent addresses a valid event object and will

call OS_Error() with error code OS_ERR_EVENT_INVALID in case of an error.

Example

static OS_EVENT _Event;

void Task(void) {

OS_TASKEVENT EventMask;

EventMask = ~0; // Request all event bits

EventMask = OS_EVENT_GetMask(&_Event, EventMask);

printf("Signales Event Bits: 0x%X\n", EventMask);

}

142 CHAPTER 5 API functions

5.2.7 OS_EVENT_GetMaskBlocked()

Description

Waits for the specified event bits, depending on the current mask mode. The signaled event

mask bits are consumed unless OS_EVENT_RESET_MODE_MANUAL is selected.

Prototype

OS_TASKEVENT OS_EVENT_GetMaskBlocked(OS_EVENT* pEvent,

OS_TASKEVENT EventMask);

Parameters

Parameter Description

pEvent Pointer to the event object that the task will be waiting for.

EventMask The event bit mask containing the event bits, which shall be

waited for.

Return value

All requested events that have been signaled and were specified in the EventMask.

Additional information

pEvent addresses an existing event object, which must be created before the call of

OS_EVENT_GetMaskBlocked(). A debug build of embOS will check whether pEvent address-

es a valid event object and will call OS_Error() with error code OS_ERR_EVENT_INVALID

in case of an error.

The state of the event object after calling OS_EVENT_GetMaskBlocked() depends on the

reset mode of the event object which was set by creating the event object by a call of

OS_EVENT_CreateEx() or OS_EVENT_SetResetMode().

Example

static OS_EVENT _Event;

void Task(void) {

...

// Waits either for the first or second, or for

// both event bits to be singaled, depending on

// the specified mask mode.

OS_EVENT_GetMaskBlocked(&_Event, 0x3);

...

}

143 CHAPTER 5 API functions

5.2.8 OS_EVENT_GetMaskMode()

Description

Retrieves the current mask mode (mask bits behavior) of an event object.

Prototype

OS_EVENT_MASK_MODE OS_EVENT_GetMaskMode(OS_CONST_PTR OS_EVENT *pEvent);

Parameters

Parameter Description

pEvent Pointer to an event object.

Return value

The mask mode which is currently set.

Modes are defined in enum OS_EVENT_MASK_MODE.

OS_EVENT_MASK_MODE_OR_LOGIC (0x00u): Mask bits are used with OR logic (default).

OS_EVENT_MASK_MODE_AND_LOGIC (0x04u): Mask bits are used with AND logic.

Additional information

pEvent must address an existing event object, which has been created before by a call of

OS_EVENT_Create() or OS_EVENT_CreateEx().

A debug build of embOS will check whether pEvent addresses a valid event object and will

call OS_Error() with error code OS_ERR_EVENT_INVALID in case of an error. Since version

4.34 of embOS, the mask mode of an event object can be controlled by the OS_EVENT_Cre-

ateEx() function or set after creation using the new function OS_EVENT_SetMaskMode().

If needed, the current setting of the mask mode can be retrieved with OS_EVENT_Get-

MaskMode().

Example

static OS_EVENT _Event;

void Task(void) {

OS_EVENT_MASK_MODE MaskMode;

MaskMode = OS_EVENT_GetMaskMode(&_Event);

if (MaskMode == OS_EVENT_MASK_MODE_OR_LOGIC) {

printf("Logic: OR\n");

} else {

printf("Logic: AND\n");

}

144 CHAPTER 5 API functions

5.2.9 OS_EVENT_GetMaskTimed()

Description

Waits for the specified event bits with timeout, depending on the current mask mode. The

task is suspended for the specified time or until the event(s) have been signaled. The

signaled event mask bits are consumed unless OS_EVENT_RESET_MODE_MANUAL is selected.

Prototype

OS_TASKEVENT OS_EVENT_GetMaskTimed(OS_EVENT* pEvent,

OS_TASKEVENT EventMask,

OS_TIME Timeout);

Parameters

Parameter Description

pEvent Pointer to the event object that the task will be waiting for.

EventMask The event bit mask containing the event bits, which shall be

waited for.

Timeout

Maximum time in embOS system ticks until the event must

be signaled. The data type OS_TIME is defined as an integer,

therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

Matching event object mask bits or 0 when a timeout occurred.

Additional information

pEvent addresses an existing event object, which must be created before the call of

OS_EVENT_GetMaskTimed(). A debug build of embOS will check whether pEvent addresses

a valid event object and will call OS_Error() with error code OS_ERR_EVENT_INVALID in

case of an error.

Example

static OS_EVENT _Event;

void Task(void) {

...

// Waits either for the first or second, or for

// both event bits to be singaled, depending on

// the specified mask mode. The task resumes after

// 1000 system ticks, if the needed event bits were not

// signaled.

OS_EVENT_GetMaskTimed(&_Event, 0x3, 1000);

...

}

145 CHAPTER 5 API functions

5.2.10 OS_EVENT_GetResetMode()

Description

Returns the reset mode (reset behavior) of an event object.

Prototype

OS_EVENT_RESET_MODE OS_EVENT_GetResetMode(OS_CONST_PTR OS_EVENT *pEvent);

Parameters

Parameter Description

pEvent Pointer to event object control structure.

Return value

The reset mode which is currently set.

Modes are defined in enum OS_EVENT_RESET_MODE.

OS_EVENT_RESET_MODE_SEMIAUTO (0x00u): As previous mode (default).

OS_EVENT_RESET_MODE_MANUAL (0x01u): Event remains set, has to be reset by task.

OS_EVENT_RESET_MODE_AUTO (0x02u): Event is reset automatically.

Additional information

pEvent must address an existing event object, which has been created before by a call of

OS_EVENT_Create() or OS_EVENT_CreateEx().

A debug build of embOS will check whether pEvent addresses a valid event object and will

call OS_Error() with error code OS_ERR_EVENT_INVALID in case of an error. Since version

3.88a of embOS, the reset mode of an event object can be controlled by the new OS_EVEN-

T_CreateEx() function or set after creation using the new function OS_EVENT_SetReset-

Mode(). If needed, the current setting of the reset mode can be retrieved with OS_EVEN-

T_GetResetMode().

Example

static OS_EVENT _Event;

void Task(void) {

OS_EVENT_RESET_MODE ResetMode;

ResetMode = OS_EVENT_GetResetMode(&_Event);

if (ResetMode == OS_EVENT_RESET_MODE_SEMIAUTO) {

printf("Reset Mode: SEMIAUTO\n");

} else if (ResetMode == OS_EVENT_RESET_MODE_MANUAL) {

printf("Reset Mode: MANUAL\n");

} else {

printf("Reset Mode: AUTO\n");

}

146 CHAPTER 5 API functions

5.2.11 OS_EVENT_GetTimed()

Description

Waits for an event and suspends the task for a specified time or until the event has been

signaled. The event is consumed unless OS_EVENT_RESET_MODE_MANUAL is selected.

Prototype

char OS_EVENT_GetTimed(OS_EVENT* pEvent,

OS_TIME Timeout);

Parameters

Parameter Description

pEvent Pointer to the event object that the task will be waiting for.

Timeout

Maximum time in embOS system ticks until the event must

be signaled. The data type OS_TIME is defined as an integer,

therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success, the event was signaled within the specified time.

1 If the event was not signaled within the specified time.

Additional information

pEvent addresses an existing event object, which must be created before the call of

OS_EVENT_GetTimed(). A debug build of embOS will check whether pEvent addresses a

valid event object and will call OS_Error() with error code OS_ERR_EVENT_INVALID in case

of an error.

Example

static OS_EVENT _Event;

void Task(void) {

...

if (OS_EVENT_GetTimed(&_Event, 1000) == 0) {

// event was signaled within timeout time, handle event

} else {

// event was not signaled within timeout time, handle timeout

}

...

}

147 CHAPTER 5 API functions

5.2.12 OS_EVENT_Pulse()

Description

Signals an event object and resumes waiting tasks, then resets the event object to non-

signaled state.

Prototype

void OS_EVENT_Pulse(OS_EVENT* pEvent);

Parameters

Parameter Description

pEvent Pointer to the event object which should be pulsed.

Additional information

If any tasks are waiting at the event object, the tasks are resumed. The event object

remains in non-signaled state, regardless the reset mode.

A debug build of embOS will check whether pEvent addresses a valid event object and will

call OS_Error() with the error code OS_ERR_EVENT_INVALID in case of an error.

Example

static OS_EVENT _Event;

void HPTask(void) {

OS_EVENT_GetBlocked(&_Event); // Suspends the task

}

void LPTask(void) {

OS_Event_Pulse(&_Event); // Signales the HPTask

}

148 CHAPTER 5 API functions

5.2.13 OS_EVENT_Reset()

Description

Resets the specified event object to non-signaled state.

Prototype

void OS_EVENT_Reset(OS_EVENT* pEvent);

Parameters

Parameter Description

pEvent Pointer to the event object which should be reset to non-sig-

naled state.

Additional information

pEvent must address an existing event object, which has been created before by a call

of OS_EVENT_Create(). A debug build of embOS will check whether pEvent addresses a

valid event object and will call OS_Error() with the error code OS_ERR_EVENT_INVALID in

case of an error.

Example

static OS_EVENT _Event;

void Task(void) {

...

OS_EVENT_Reset(&_Event);

...

}

149 CHAPTER 5 API functions

5.2.14 OS_EVENT_Set()

Description

Sets an event object to signaled state, or resumes tasks which are waiting at the event

object.

Prototype

void OS_EVENT_Set(OS_EVENT* pEvent);

Parameters

Parameter Description

pEvent Pointer to the event object.

Additional information

pEvent must address an existing event object, which must be created before by a call to

OS_EVENT_Create(). A debug build of embOS will check whether pEvent addresses a valid

event object and will call OS_Error() with error code OS_ERR_EVENT_INVALID in case of

an error.

If no tasks are waiting at the event object, the event object is set to signaled state. Any

task that is already waiting for the event object will be resumed. The state of the event

object after calling OS_EVENT_Set() then depends on the reset mode of the event object.

• With reset mode OS_EVENT_RESET_MODE_SEMIAUTO:

This is the default mode when the event object was created with OS_EVENT_Create().

This was the only mode available in embOS versions prior version 3.88a. If tasks were

waiting, the event is reset when the waiting tasks are resumed.

• With reset mode OS_EVENT_RESET_MODE_AUTO:

The event object is automatically reset when waiting tasks are resumed and continue

operation.

• With reset mode OS_EVENT_RESET_MODE_MANUAL:

The event object remains signaled when waiting tasks are resumed and continue

operation. The event object must be reset by the calling task.

Example

Examples on how to use the OS_EVENT_Set() function are shown in Examples of using

event objects on page 132.

150 CHAPTER 5 API functions

5.2.15 OS_EVENT_SetMask()

Description

Sets the event mask bits of an event object.

Prototype

void OS_EVENT_SetMask(OS_EVENT* pEvent,

OS_TASKEVENT EventMask);

Parameters

Parameter Description

pEvent Pointer to the event object.

EventMask The event bit mask containing the event bits, which shall be

signaled.

Additional information

pEvent must address an existing event object, which must be created before by a call to

OS_EVENT_Create(). A debug build of embOS will check whether pEvent addresses a valid

event object and will call OS_Error() with error code OS_ERR_EVENT_INVALID in case of

an error.

Any task that is already waiting for matching event mask bits on this event object will be

resumed. OS_EVENT_SetMask() does not clear any event mask bits.

Example

static OS_EVENT _Event;

void Task(void) {

OS_TASKEVENT EventMask;

...

EventMask = 1 << ((sizeof(OS_TASKEVENT) * 8) - 1); // Set MSB event bit

OS_EVENT_SetMask(&_Event, EventMask); // Signal MSB event bit

...

}

151 CHAPTER 5 API functions

5.2.16 OS_EVENT_SetMaskMode()

Description

Sets the mask mode of an event object to OR/AND logic.

Prototype

void OS_EVENT_SetMaskMode(OS_EVENT* pEvent,

OS_EVENT_MASK_MODE MaskMode);

Parameters

Parameter Description

pEvent Pointer to an event object.

MaskMode

Event Mask mode.

Modes are defined in enum OS_EVENT_MASK_MODE.

OS_EVENT_MASK_MODE_OR_LOGIC (0x00u): Mask bits are used

with OR logic (default).

OS_EVENT_MASK_MODE_AND_LOGIC (0x04u): Mask bits are

used with AND logic.

Additional information

pEvent must address an existing event object, which has been created before by a call of

OS_EVENT_Create() or OS_EVENT_CreateEx().

A debug build of embOS will check whether pEvent addresses a valid event object and will

call OS_Error() with error code OS_ERR_EVENT_INVALID in case of an error.

Since version 4.34 of embOS, the mask bits behavior of the event object can be controlled

by different mask modes which may be passed to the new function OS_EVENT_CreateEx()

or may be modified by a call of OS_EVENT_SetMaskMode(). The following mask modes are

defined and can be used as parameter:

•OS_EVENT_MASK_MODE_OR_LOGIC:

This mask mode is the default mode. Only one of the bits specified in the event object

bit mask must be signaled.

•OS_EVENT_MASK_MODE_AND_LOGIC:

With this mode all specified event mask bits must be signaled.

Example

static OS_EVENT _Event;

void Task(void) {

...

// Set the mask mode for the event object to AND logic

OS_EVENT_SetMaskMode(&_Event, OS_EVENT_MASK_MODE_AND_LOGIC);

...

}

152 CHAPTER 5 API functions

5.2.17 OS_EVENT_SetResetMode()

Description

Sets the reset behavior of an event object to auto-matic, manual or semiauto.

Prototype

void OS_EVENT_SetResetMode(OS_EVENT* pEvent,

OS_EVENT_RESET_MODE ResetMode);

Parameters

Parameter Description

pEvent Pointer to an event object.

ResetMode

Controls the reset mode of the event object.

OS_EVENT_RESET_DEFAULT (0x00u): As previous mode.

OS_EVENT_RESET_MANUAL (0x01u): Event remains set, has to

be reset by task.

OS_EVENT_RESET_AUTO (0x02u): Event is reset automatically.

Additional information

pEvent must address an existing event object, which has been created before by a call of

OS_EVENT_Create() or OS_EVENT_CreateEx().

A debug build of embOS will check whether pEvent addresses a valid event object and will

call OS_Error() with error code OS_ERR_EVENT_INVALID in case of an error.

Implementation of event objects in embOS versions before 3.88a unfortunately was not

consistent with respect to the state of the event after calling OS_EVENT_Set() or OS_EVEN-

T_GetBlocked() functions. The state of the event was different when tasks were waiting

or not.

Since embOS version 3.88a, the state of the event (reset behavior) can be controlled after

creation by the new function OS_EVENT_SetResetMode(), or during creation by the new

OS_EVENT_CreateEx() function. The following reset modes are defined and can be used

as parameter:

•OS_EVENT_RESET_MODE_SEMIAUTO:

This reset mode is the default mode used with all previous versions of embOS. The

reset behavior unfortunately is not consistent and depends on the function called to

set or wait for an event. This reset mode is defined for compatibility with older embOS

versions (prior version 3.88a). Calling OS_EVENT_Create() sets the reset mode to

OS_EVENT_RESET_MODE_SEMIAUTO to be compatible with older embOS versions.

•OS_EVENT_RESET_MODE_AUTO:

This mode sets the reset behavior of an event object to automatic clear. When an event

is set, all waiting tasks are resumed and the event is cleared automatically. An exception

to this is when a task called OS_EVENT_GetTimed() and the timeout expired before the

event was signaled, in which case the function returns with timeout and the event is

not cleared automatically.

•OS_EVENT_RESET_MODE_MANUAL:

This mode sets the event to manual reset mode. When an event is set, all waiting tasks

are resumed and the event object remains signaled. The event must be reset by one

task which was waiting for the event.

Example

static OS_EVENT _Event;

void Task(void) {

// Set the reset mode for the event object to manual

OS_EVENT_SetResetMode(&_Event, OS_EVENT_RESET_MANUAL);

153 CHAPTER 5 API functions

}

Chapter 6

Mutexes

155 CHAPTER 6 Introduction

6.1 Introduction

Mutexes are used for managing resources by avoiding conflicts caused by simultaneous

use of a resource. The resource managed can be of any kind: a part of the program that is

not reentrant, a piece of hardware like the display, a flash prom that can only be written

to by a single task at a time, a motor in a CNC control that can only be controlled by one

task at a time, and a lot more.

The basic procedure is as follows:

Any task that uses a resource first claims it calling the OS_MUTEX_LockBlocked() or OS_MU-

TEX_Lock() routines of embOS. If the mutex is available, the program execution of the

task continues, but the mutex is blocked for other tasks. If a second task now tries to

acquire the same mutex while it is in use by the first task, this second task is suspended

until the first task releases the mutex. However, if the first task that uses the mutex calls

OS_MUTEX_LockBlocked() again for that mutex, it is not suspended because the mutex is

blocked only for other tasks.

The following diagram illustrates the process of using a mutex:

A mutex contains a counter that keeps track of how many times the mutex has been

claimed by calling OS_MUTEX_Lock() or OS_MUTEX_LockBlocked() by a particular task. It

is released when that counter reaches zero, which means the OS_MUTEX_Unlock() routine

must be called exactly the same number of times as OS_MUTEX_LockBlocked() or OS_MU-

TEX_Lock(). If it is not, the mutex remains blocked for other tasks.

On the other hand, a task cannot release a mutex that it does not own by calling OS_MU-

TEX_Unlock(). In debug builds of embOS, a call of OS_MUTEX_Unlock() for a mutex that

is not owned by this task will result in a call to the error handler OS_Error().

156 CHAPTER 6 Introduction

Example of using a mutex

Here, two tasks access a (debug) terminal completely independently from each other. The

terminal is a resource that needs to be protected with a mutex. One task may not interrupt

another task which is writing to the terminal, as otherwise the following might occur:

• Task A begins writing to the terminal

• Task B interrupts Task A and writes to the terminal

• Task A is resumed and its output is written at a wrong position

To avoid this type of situation, every time the terminal is to be accessed by a task it is

first claimed by a call to OS_MUTEX_LockBlocked() (and is automatically waited for if the

mutex is blocked). After the terminal has been written to, it is released by a call to OS_MU-

TEX_Unlock().

The sample application file OS_RSema.c delivered in the application samples folder of embOS

demonstrates how mutex can be used in the above scenario:

#include "RTOS.h"

#include <stdio.h>

static OS_STACKPTR int StackHP[128], StackLP[128]; /* Task stacks */

static OS_TASK TCBHP, TCBLP; /* Task-control-blocks */

/****** Local function **********************************************/

static void _Write(char const* s) {

OS_MUTEX_LockBlocked(&Mutex);

printf(s);

OS_MUTEX_Unlock(&Mutex);

}

/****** Task functions **********************************************/

static void HPTask(void) {

while (1) {

_Write("HPTask\n");

OS_TASK_Delay(50);

}

static void LPTask(void) {

while (1) {

_Write("LPTask\n");

OS_TASK_Delay(200);

}

/*********************************************************************

* main()

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize hardware for embOS

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_MUTEX_Create(&Mutex); // Creates mutex

OS_Start(); // Start multitasking

return 0;

}

/****** End Of File *************************************************/

157 CHAPTER 6 API functions

6.2 API functions

Routine Description

main

Task

ISR

Timer

OS_MUTEX_Create() Creates a mutex. ● ●

OS_MUTEX_Delete() Deletes a specified mutex. ● ●

OS_MUTEX_GetOwner() Returns the mutex owner if any. ● ●

OS_MUTEX_GetValue() Returns the value of the usage counter of a

specified mutex. ● ●

OS_MUTEX_Lock() Requests a specified mutex and blocks it for

other tasks if it is available. ● ●

OS_MUTEX_LockBlocked() Claims a mutex and blocks it for other tasks. ● ●

OS_MUTEX_LockTimed() Tries to claim a mutex and blocks it for other

tasks if it is available within a specified time. ● ●

OS_MUTEX_Unlock() Releases a mutex currently in use by a task. ● ●

158 CHAPTER 6 API functions

6.2.1 OS_MUTEX_Create()

Description

Creates a mutex.

Prototype

void OS_MUTEX_Create(OS_MUTEX* pMutex);

Parameters

Parameter Description

pMutex Pointer to the data structure for a mutex.

Additional information

After creation, the mutex is not blocked; the value of the counter is zero.

Example

static OS_MUTEX _Mutex;

int main(void) {

...

OS_MUTEX_Create(&_Mutex);

...

return 0;

}

159 CHAPTER 6 API functions

6.2.2 OS_MUTEX_Delete()

Description

Deletes a specified mutex. The memory of that mutex may be reused for other purposes

or may be used for creating another mutex using the same memory.

Prototype

void OS_MUTEX_Delete(OS_MUTEX* pMutex);

Parameters

Parameter Description

pMutex Pointer to a data structure of type OS_MUTEX.

Additional information

Before deleting a mutex, make sure that no task is claiming the mutex. A debug build of

embOS will call OS_Error() with the error code OS_ERR_MUTEX_DELETE if a mutex is deleted

when it is already in use. In systems with dynamic creation of mutexes, you must delete a

mutex before recreating it. Failure to so may cause mutex handling to work incorrectly.

Example

static OS_MUTEX _Mutex;

int Task(void) {

...

OS_MUTEX_Delete(&_Mutex);

...

return 0;

}

160 CHAPTER 6 API functions

6.2.3 OS_MUTEX_GetOwner()

Description

Returns the mutex owner if any. When a task is currently using (blocking) the mutex the

task Id (address of task according task control block) is returned.

Prototype

OS_TASK *OS_MUTEX_GetOwner(OS_CONST_PTR OS_MUTEX *pMutex);

Parameters

Parameter Description

pMutex Pointer to the data structure for a mutex.

Return value

= NULL The mutex is not used by any task.

≠ NULL Task Id (address of the task control block).

Additional information

If a mutex was used in main() the return value of OS_MUTEX_GetOwner() is ambiguous.

The return value NULL can mean it is currently used in main() or it is currently unused.

Therefore, OS_MUTEX_GetOwner() must not be used to check if a mutex is available. Please

use OS_MUTEX_GetValue() instead.

It is also good practice to free all used mutexes in main() before calling OS_Start().

Example

Please find an example at OS_MUTEX_GetValue().

161 CHAPTER 6 API functions

6.2.4 OS_MUTEX_GetValue()

Description

Returns the value of the usage counter of a specified mutex.

Prototype

int OS_MUTEX_GetValue(OS_CONST_PTR OS_MUTEX *pMutex);

Parameters

Parameter Description

pMutex Pointer to the data structure for a mutex.

Return value

The counter value of the mutex.

A value of zero means the mutex is available.

Example

static OS_MUTEX _Mutex;

void CheckMutex(void) {

int Value;

OS_TASK* Owner;

Value = OS_MUTEX_GetValue(&_Mutex);

if (Value == 0) {

printf("Mutex is currently unused");

} else {

Owner = OS_MUTEX_GetOwner(&_Mutex);

if (Owner == NULL) {

printf("Mutex was used in main()");

} else {

printf("Mutex is currently used in task 0x%X", Owner);

}

162 CHAPTER 6 API functions

6.2.5 OS_MUTEX_Lock()

Description

Requests a specified mutex and blocks it for other tasks if it is available. Continues execution

in any case.

Prototype

char OS_MUTEX_Lock(OS_MUTEX* pMutex);

Parameters

Parameter Description

pMutex Pointer to the data structure for a mutex.

Return value

1 Mutex was available, now in use by calling task.

0 Mutex was not available.

Additional information

The following diagram illustrates how OS_MUTEX_Lock() works:

Example

if (OS_MUTEX_Lock(&Mutex_LCD)) {

DispTime(); // Access the resource LCD

OS_MUTEX_Unlock(&Mutex_LCD); // Resource LCD is no longer needed

} else {

... // Do something else

}

163 CHAPTER 6 API functions

6.2.6 OS_MUTEX_LockBlocked()

Description

Claims a mutex and blocks it for other tasks.

Prototype

int OS_MUTEX_LockBlocked(OS_MUTEX* pMutex);

Parameters

Parameter Description

pMutex Pointer to the data structure for a mutex.

Return value

The counter value of the mutex.

A value greater than one denotes the mutex was already locked by the calling task.

Additional information

The following situations are possible:

• Case A: The mutex is not in use.

If the mutex is not used by a task, which means the counter of the mutex is zero, the

mutex will be blocked for other tasks by incrementing the counter and writing a unique

code for the task that uses it into the mutex.

• Case B: The mutex is used by this task.

The counter of the mutex is incremented. The program continues without a break.

• Case C: The mutex is being used by another task.

The execution of this task is suspended until the mutex is released. In the meantime if

the task blocked by the mutex has a higher priority than the task blocking the mutex,

the blocking task is assigned the priority of the task requesting the mutex. This is called

priority inheritance. Priority inheritance can only temporarily increase the priority of a

task, never reduce it.

An unlimited number of tasks can wait for a mutex. According to the rules of the scheduler,

of all the tasks waiting for the mutex the task with the highest priority will acquire the

mutex and continue program execution.

Example

static OS_MUTEX _Mutex;

void Task(void) {

...

OS_MUTEX_LockBlocked(&_Mutex);

...

OS_MUTEX_Unlock(&_Mutex);

...

}

The following diagram illustrates how OS_MUTEX_LockBlocked() works:

164 CHAPTER 6 API functions

6.2.7 OS_MUTEX_LockTimed()

Description

Tries to claim a mutex and blocks it for other tasks if it is available within a specified time.

Prototype

int OS_MUTEX_LockTimed(OS_MUTEX* pMutex,

OS_TIME TimeOut);

Parameters

Parameter Description

pMutex Pointer to the data structure of a mutex.

TimeOut

Maximum time until the mutex should be available. Timer

period in embOS system ticks. The data type OS_TIME is de-

fined as an integer, therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

= 0 Failed, mutex not available before timeout.

≠ 0 Success, mutex available, current usage count of mutex.

A value greater than one denotes the mutex was already locked by the calling task.

Additional information

The following situations are possible:

• Case A: The mutex is not in use.

If the mutex is not used by a task, which means the counter of the mutex is zero, the

mutex will be blocked for other tasks by incrementing the counter and writing a unique

code for the task that uses it into the mutex.

• Case B: The mutex is used by this task.

The counter of the mutex is incremented. The program continues without a break.

• Case C: The mutex is being used by another task.

The execution of this task is suspended until the mutex is released or the timeout time

expired. In the meantime if the task blocked by the mutex mutex has a higher priority

than the task blocking the mutex, the blocking task is assigned the priority of the task

requesting the mutex. This is called priority inheritance. Priority inheritance can only

temporarily increase the priority of a task, never reduce it.

If the mutex becomes available during the timeout, the calling task claims the mutex

and the function returns a value greater than zero, otherwise, if the mutex does not

become available, the function returns zero.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that the mutex becomes available before the calling task is resumed.

Anyhow, the function will not claim the mutex because it was not available within the

requested time.

An unlimited number of tasks can wait for a mutex. According to the rules of the scheduler,

of all the tasks waiting for the mutex the task with the highest priority will acquire the

mutex and continue program execution.

OS_MUTEX_LockTimed() could cause a priority inheritance. In case of a timeout the priority

inheritance must be handled.

165 CHAPTER 6 API functions

Example

static OS_MUTEX _Mutex;

void Task(void) {

...

if (OS_MUTEX_LockTimed(&_Mutex, 100)) {

... // Mutex acquired

} else {

... // Timeout

}

...

}

166 CHAPTER 6 API functions

6.2.8 OS_MUTEX_Unlock()

Description

Releases a mutex currently in use by a task.

Prototype

void OS_MUTEX_Unlock(OS_MUTEX* pMutex);

Parameters

Parameter Description

pMutex Pointer to mutex control structure.

Additional information

OS_MUTEX_Unlock() may be used on a mutex only after that mutex has been used by

calling OS_MUTEX_LockBlocked() or OS_MUTEX_Lock(). OS_MUTEX_Unlock() decrements

the usage counter of the mutex which must never become negative. If this counter be-

comes negative, a debug build will call the embOS error handler OS_Error() with error

code OS_ERR_UNUSE_BEFORE_USE. In a debug build OS_Error() will also be called if OS_MU-

TEX_Unlock() is called from a task which does not own the mutex. The error code is OS_ER-

R_RESOURCE_OWNER in this case.

Example

Please find an example at OS_MUTEX_Lock().

Chapter 7

Semaphores

168 CHAPTER 7 Introduction

7.1 Introduction

A semaphore is a variable or abstract data type used to control access to a common resource

by multiple processes in a multitasking operating system. While not as widely used as

mutexes, events or mailboxes, semaphores can be very useful in specific situations. For

example, they are commonly used in “credittracking synchronization” where a task needs

to wait for something that can be signaled one or more times.

Example of using semaphores

Here, an interrupt is issued every time data is received from a peripheral source. The in-

terrupt service routine then signals the arrival of data to a worker task, which subsequently

processes that data. When the worker task is blocked from exection, e.g. by a higher-pri-

ority task, the semaphore’s counter effectively tracks the number of data packets to be

processed by the worker task, which will be executed for that exact number of times when

resumed.

The following sample application shows how semaphores can be used in the above scenario:

#include "RTOS.h"

#include <stdio.h>

static OS_STACKPTR int Stack[128]; // Task stack

static OS_TASK TCB; // Task control block

static OS_SEMAPHORE Sema; // Semaphore

static OS_TICK_HOOK Hook; // Hook to emulate external interrupt

void Task(void) {

while(1) {

OS_SEMAPHORE_TakeBlocked(&Sema); // Wait for signaling of received data

printf("Task is processing data"); // Act on received data

}

void OnTickHookFunction(void) {

OS_SEMAPHORE_Give(&Sema); // Signal data reception

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

// Register tick hook function to emulate an external interrupt

OS_TICK_AddHook(&Hook, (OS_TICK_HOOK_ROUTINE*)OnTickHookFunction);

OS_TASK_CREATE(&TCB, "Task", 100, Task, Stack);

OS_SEMAPHORE_CREATE(&Sema); // Creates semaphore

OS_Start(); // Start embOS

return 0;

}

169 CHAPTER 7 API functions

7.2 API functions

Routine Description

main

Task

ISR

Timer

OS_SEMAPHORE_CREATE() Macro that creates a semaphore with an

initial count value of zero. ● ●

OS_SEMAPHORE_Create() Creates a counting semaphore with a

specified initial count value. ● ●

OS_SEMAPHORE_Delete() Deletes a counting semaphore. ● ●

OS_SEMAPHORE_Give() Increments the counter of a semaphore. ● ● ● ●

OS_SEMAPHORE_GiveMax() Increments the counter of a semaphore

up to a specified maximum value. ●●●●

OS_SEMAPHORE_GetValue() Returns the current counter value of a

specified semaphore. ●●●●

OS_SEMAPHORE_SetValue() Sets the counter value of a specified sem-

aphore. ● ●

OS_SEMAPHORE_Take() Decrements the counter of a semaphore,

if it was signaled. ●●●●

OS_SEMAPHORE_TakeBlocked() Decrements the counter of a semaphore. ● ●

OS_SEMAPHORE_TakeTimed() Decrements a semaphore counter if the

semaphore is available within a specified

time.

● ●

170 CHAPTER 7 API functions

7.2.1 OS_SEMAPHORE_CREATE()

Description

Macro that creates a semaphore with an initial count value of zero.

Prototype

void OS_SEMAPHORE_CREATE(OS_SEMAPHORE* pSema);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

Additional information

To create a semaphore a data structure of the type OS_SEMAPHORE must be defined in

memory and initialized using OS_SEMAPHORE_CREATE(). The value of a semaphore created

through this macro is zero. If you need to create a semaphore with an arbitrary initial

counting value, use the function OS_SEMAPHORE_Create().

Example

Please refer to the example in Introduction on page 168.

171 CHAPTER 7 API functions

7.2.2 OS_SEMAPHORE_Create()

Description

Creates a counting semaphore with a specified initial count value.

Prototype

void OS_SEMAPHORE_Create(OS_SEMAPHORE* pSema,

OS_UINT InitValue);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

InitValue

Initial count value of the semaphore:

0 ≤ InitValue ≤ 216 - 1 = 0xFFFF for 8/16 bit CPUs.

0 ≤ InitValue ≤ 232 - 1 = 0xFFFFFFFF for 32 bit CPUs.

Additional information

To create a counting semaphore a data structure of the type OS_SEMAPHORE must be defined

in memory and initialized using OS_SEMAPHORE_Create().

Example

static OS_SEMA _Sema;

int main(void) {

...

OS_SEMAPHORE_Create(&_Sema, 8);

...

return 0;

}

172 CHAPTER 7 API functions

7.2.3 OS_SEMAPHORE_Delete()

Description

Deletes a counting semaphore.

Prototype

void OS_SEMAPHORE_Delete(OS_SEMAPHORE* pSema);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

Additional information

Before deleting a semaphore, make sure that no task is waiting for it and that no task will

signal that semaphore at a later point.

A debug build of embOS will reflect an error if a deleted semaphore is signaled.

Example

static OS_SEMA _Sema;

void Task(void) {

...

OS_SEMAPHORE_Delete(&_Sema);

...

}

173 CHAPTER 7 API functions

7.2.4 OS_SEMAPHORE_Give()

Description

Increments the counter of a semaphore.

Prototype

void OS_SEMAPHORE_Give(OS_SEMAPHORE* pSema);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

Additional information

OS_SEMAPHORE_Give() signals an event to a semaphore by incrementing its counter. If one

or more tasks are waiting for an event to be signaled to this semaphore, the task with

the highest priority becomes the running task. The counter can have a maximum value

of 0xFFFF for 8/16 bit CPUs or 0xFFFFFFFF for 32 bit CPUs. It is the responsibility of the

application to make sure that this limit is not exceeded. A debug build of embOS detects

a counter overflow and calls OS_Error() with error code OS_ERR_SEMAPHORE_OVERFLOW if

an overflow occurs.

Example

Please refer to the example in Introduction on page 168.

174 CHAPTER 7 API functions

7.2.5 OS_SEMAPHORE_GiveMax()

Description

Increments the counter of a semaphore up to a specified maximum value.

Prototype

void OS_SEMAPHORE_GiveMax(OS_SEMAPHORE* pSema,

OS_UINT MaxValue);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

MaxValue

Count value of the semaphore:

1 ≤ MaxValue ≤ 216 - 1 = 0xFFFF for 8/16 bit CPUs.

1 ≤ MaxValue ≤ 232 - 1 = 0xFFFFFFFF for 32 bit CPUs.

Additional information

As long as current value of the semaphore counter is below the specified maximum value,

OS_SEMAPHORE_GiveMax() signals an event to a semaphore by incrementing its counter. If

one or more tasks are waiting for an event to be signaled to this semaphore, the tasks are

placed into the READY state and the task with the highest priority becomes the running task.

Calling OS_SEMAPHORE_GiveMax() with a MaxValue of 1 makes a counting semaphore be-

have like a mutex. Consider using a mutex instead.

Example

static OS_SEMA _Sema;

void Task(void) {

...

OS_SEMAPHORE_GiveMax(&_Sema, 8);

...

}

175 CHAPTER 7 API functions

7.2.6 OS_SEMAPHORE_GetValue()

Description

Returns the current counter value of a specified semaphore.

Prototype

int OS_SEMAPHORE_GetValue(OS_CONST_PTR OS_SEMAPHORE *pSema);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

Return value

The current counter value of the semaphore.

Example

static OS_SEMA _Sema;

void PrintSemaValue(void) {

int Value;

Value = OS_SEMAPHORE_GetValue(&_Sema);

printf("Sema Value: %d\n", Value)

}

176 CHAPTER 7 API functions

7.2.7 OS_SEMAPHORE_SetValue()

Description

Sets the counter value of a specified semaphore.

Prototype

OS_U8 OS_SEMAPHORE_SetValue(OS_SEMAPHORE* pSema,

OS_UINT Value);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

Value

Count value of the semaphore:

0 ≤ Value ≤ 216 - 1 = 0xFFFF for 8/16 bit CPUs.

0 ≤ Value ≤ 232 - 1 = 0xFFFFFFFF for 32 bit CPUs.

Return value

0 In any case. The return value can safely be ignored.

Example

static OS_SEMA _Sema;

void Task(void) {

...

OS_SEMAPHORE_SetValue(&_Sema, 0);

...

}

177 CHAPTER 7 API functions

7.2.8 OS_SEMAPHORE_Take()

Description

Decrements the counter of a semaphore, if it was signaled.

Prototype

OS_BOOL OS_SEMAPHORE_Take(OS_SEMAPHORE* pSema);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

Return value

0 Failed, semaphore was not signaled before the call.

1 Success, semaphore was available and counter was decremented once.

Additional information

If the counter of the semaphore is not zero, the counter is decremented and program

execution continues.

If the counter is zero, OS_SEMAPHORE_Take() does not wait and does not modify the sem-

aphore counter.

Example

static OS_SEMA _Sema;

void Task(void) {

...

if (OS_SEMAPHORE_Take(&_Sema) == 1) {

printf("Semaphore decremented successfully.\n");

} else {

printf("Semaphore not signaled.\n");

}

...

}

178 CHAPTER 7 API functions

7.2.9 OS_SEMAPHORE_TakeBlocked()

Description

Decrements the counter of a semaphore.

Prototype

void OS_SEMAPHORE_TakeBlocked(OS_SEMAPHORE* pSema);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

Additional information

If the counter of the semaphore is not zero, the counter is decremented and program

execution continues.

If the counter is zero, OS_SEMAPHORE_TakeBlocked() waits until the counter is incremented

by another task, a timer or an interrupt handler by a call to OS_SEMAPHORE_Give(). The

counter is then decremented and program execution continues. An unlimited number of

tasks can wait for a semaphore. According to the rules of the scheduler, of all the tasks

waiting for the semaphore, the task with the highest priority will continue program exe-

cution.

Example

Please refer to the example in Introduction on page 168.

179 CHAPTER 7 API functions

7.2.10 OS_SEMAPHORE_TakeTimed()

Description

Decrements a semaphore counter if the semaphore is available within a specified time.

Prototype

OS_BOOL OS_SEMAPHORE_TakeTimed(OS_SEMAPHORE* pSema,

OS_TIME TimeOut);

Parameters

Parameter Description

pSema Pointer to a data structure of type OS_SEMAPHORE.

TimeOut

Maximum time until semaphore should be available. Timer

period in embOS system ticks. The data type OS_TIME is de-

fined as an integer, therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Failed, semaphore not available before timeout.

1 Success, semaphore was available and counter decremented.

Additional information

If the counter of the semaphore is not zero, the counter is decremented and program

execution continues.

If the counter is zero, OS_SEMAPHORE_TakeTimed() waits until the semaphore is signaled

by another task, a timer, or an interrupt handler by a call to OS_SEMAPHORE_Give(). The

counter is then decremented and program execution continues. If the semaphore was not

signaled within the specified time the program execution continues, but returns a value of

zero. An unlimited number of tasks can wait for a semaphore. According to the rules of

the scheduler, of all the tasks waiting for the semaphore, the task with the highest priority

will continue program execution.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that the counting semaphore becomes available after the timeout

expired, but before the calling task is resumed. Anyhow, the function returns with timeout,

because the semaphore was not available within the requested time. In this case, the state

of the semaphore is not modified by OS_SEMAPHORE_TakeTimed().

Example

static OS_SEMA _Sema;

void Task(void) {

...

if (OS_SEMAPHORE_TakeTimed(&_Sema, 100)) {

... // Semaphore acquired

} else {

... // Timeout

}

...

}

Chapter 8

Mailboxes

181 CHAPTER 8 Introduction

8.1 Introduction

In the preceding chapters, task synchronization by the use of semaphores was described.

Unfortunately, semaphores cannot transfer data from one task to another. If we need to

transfer data between tasks for example via a buffer, we could use a mutex every time we

accessed the buffer. But doing so would make the program less efficient. Another major

disadvantage would be that we could not access the buffer from an interrupt handler,

because the interrupt handler is not allowed to wait for the mutex.

One solution would be the usage of global variables. In this case we would need to disable

interrupts each time and in each place that we accessed these variables. This is possible,

but it is a path full of pitfalls. It is also not easy for a task to wait for a character to be

placed in a buffer without polling the global variable that contains the number of characters

in the buffer. Again, there is solution – the task could be notified by an event signaled to

the task each time a character is placed in the buffer. This is why there is an easier way to

do this with a real-time OS: The use of mailboxes.

A mailbox is a buffer that is managed by the real-time operating system. The buffer behaves

like a normal buffer; you can deposit something (called a message) and retrieve it later.

Mailboxes usually work as FIFO: first in, first out. So a message that is deposited first will

usually be retrieved first. “Message” might sound abstract, but very simply it means “item

of data”. It will become clearer in the typical applications explained in the following section.

Limitations:

Both the number of mailboxes and buffers are limited only by the amount of available

memory. However, the number of messages per mailbox, the message size per mailbox,

and the buffer size per mailbox are limited by software design.

Number of messages on 8 or 16bit CPUs:

1 <= x <= 215 - 1 = 0x7FFF

Number of messages on 32bit CPUs:

1 <= x <= 231 - 1 = 0x7FFFFFFF

Message size in bytes on 8 or 16bit CPUs:

1 <= x <= 215 - 1 = 0x7FFF

Message size in bytes on 32bit CPUs:

1 <= x <= 215 - 1 = 0x7FFF

Maximum buffer size in bytes for one mailbox on 8 or 16bit CPUs:

216 = 0xFFFF

Maximum buffer size in bytes for one mailbox on 32bit CPUs:

232 = 0xFFFFFFFF

These limitations have been placed on mailboxes to guarantee efficient coding and also to

ensure efficient management. These limitations are typically not a problem.

A mailbox can be used by more than one producer, but must be used by one consumer

only. This means that more than one task or interrupt handler is allowed to deposit new

data into the mailbox, but it does not make sense to retrieve messages by multiple tasks.

182 CHAPTER 8 Introduction

8.1.1 Single-byte mailbox functions

In many (if not the most) situations, mailboxes are used simply to hold and transfer sin-

gle-byte messages. This is the case, for example, with a mailbox that takes the character

received or sent via serial interface, or typically with a mailbox used as a keyboard buffer.

In some of these cases, time is very critical, especially if a lot of data is transferred in short

periods of time.

To minimize the overhead caused by the mailbox management of embOS, variations

on some mailbox functions are available for single-byte mailboxes. The general func-

tions OS_MAILBOX_PutBlocked(), OS_MAILBOX_Put(), OS_MAILBOX_GetBlocked(), and

OS_MAILBOX_Get() can transfer messages of sizes between 1 and 32,767 bytes each.

Their single-byte equivalents OS_MAILBOX_PutBlocked1(), OS_MAILBOX_Put1(), OS_MAIL-

BOX_GetBlocked1(), and OS_MAILBOX_Get1() work the same way with the exception that

they execute much faster because management is simpler. It is recommended to use the

singlebyte versions if you transfer a lot of single-byte data via mailboxes.

The routines OS_MAILBOX_PutBlocked1(), OS_MAILBOX_Put1(), OS_MAILBOX_Get-

Blocked1(), and OS_MAILBOX_Get1() work exactly the same way as their universal equiv-

alents. The only difference is that they must only be used for single-byte mailboxes.

183 CHAPTER 8 Introduction

Example

#define MAX_MSG_SIZE (9) // Max. number of bytes per message

#define MAX_MSG_NUM (2) // Max. number of messages per Mailbox

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task control blocks

static OS_MAILBOX MyMailbox;

static char MyMailboxBuffer[MAX_MSG_SIZE * MAX_MSG_NUM];

static void HPTask(void) {

char aData[MAX_MSG_SIZE];

while (1) {

OS_MAILBOX_GetBlocked(&MyMailbox, (void *)aData);

OS_COM_SendString(aData);

}

static void LPTask(void) {

while (1) {

OS_MAILBOX_PutBlocked(&MyMailbox, "\nHello\0");

OS_MAILBOX_PutBlocked(&MyMailbox, "\nWorld !\0");

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_MAILBOX_Create(&MyMailbox, MAX_MSG_SIZE, MAX_MSG_NUM, &MyMailboxBuffer);

OS_COM_SendString("embOS OS_Mailbox example");

OS_COM_SendString("\n\nDemonstrating message passing\n");

OS_Start(); // Start embOS

return 0;

}

184 CHAPTER 8 API functions

8.2 API functions

Routine Description

main

Task

ISR

Timer

OS_MAILBOX_Clear() Clears all messages in the specified mail-

box. ●●●●

OS_MAILBOX_Create() Creates a new mailbox. ● ●

OS_MAILBOX_Delete() Deletes a specified mailbox. ● ●

OS_MAILBOX_Get() Retrieves a new message of a predefined

size from a mailbox if a message is avail-

able.

●●●●

OS_MAILBOX_Get1() Retrieves a new message of size 1 from a

mailbox if a message is available. ●●●●

OS_MAILBOX_GetBlocked() Retrieves a new message of a predefined

size from a mailbox. ●

OS_MAILBOX_GetBlocked1() Retrieves a new message of size 1 from a

mailbox. ●

OS_MAILBOX_GetMessageCnt() Returns the number of messages current-

ly available in a specified mailbox. ●●●●

OS_MAILBOX_GetTimed() Retrieves a new message of a predefined

size from a mailbox if a message is avail-

able within a given time.

●

OS_MAILBOX_GetTimed1() Retrieves a new message of size 1 from a

mailbox if a message is available within a

given time.

●

OS_MAILBOX_GetPtr() Retrieves a pointer to a new message of a

predefined size from a mailbox, if a mes-

sage is available.

●●●●

OS_MAILBOX_GetPtrBlocked() Retrieves a pointer to a new message of a

predefined size from a mailbox. ●

OS_MAILBOX_Peek() Peeks a mail from a mailbox without re-

moving the mail. ●●●●

OS_MAILBOX_Purge() Deletes the last retrieved message in a

mailbox. ●●●●

OS_MAILBOX_Put() Stores a new message of a predefined

size in a mailbox if the mailbox is able to

accept one more message.

●●●●

OS_MAILBOX_Put1() Stores a new message of size 1 in a mail-

box if the mailbox is able to accept one

more message.

●●●●

OS_MAILBOX_PutBlocked() Stores a new message of a predefined

size in a mailbox. ●

OS_MAILBOX_PutBlocked1() Stores a new message of size 1 in a mail-

box. ●

OS_MAILBOX_PutFront()

Stores a new message of a predefined

size into a mailbox in front of all other

messages if the mailbox is able to accept

one more message.

●●●●

OS_MAILBOX_PutFront1() Stores a new message of size 1 into a

mailbox in front of all other messages if ●●●●

185 CHAPTER 8 API functions

Routine Description

main

Task

ISR

Timer

the mailbox is able to accept one more

message.

OS_MAILBOX_PutFront-

Blocked()

Stores a new message of a predefined

size at the beginning of a mailbox in front

of all other messages.

●

OS_MAILBOX_PutFront-

Blocked1()

Stores a new message of size 1 at the be-

ginning of a mailbox in front of all other

messages.

●

OS_MAILBOX_PutTimed()

Stores a new message of a predefined

size in a mailbox if the mailbox is able to

accept one more message within a given

time.

●

OS_MAILBOX_PutTimed1() Stores a new message of size 1 in a mail-

box if the mailbox is able to accept one

more message within a given time.

●

OS_MAILBOX_WaitBlocked() Waits until a mail is available, but does

not retrieve the message from the mail-

box.

●

OS_MAILBOX_WaitTimed() Waits until a mail is available or the time-

out has expired, but does not retrieve the

message from the mailbox.

●

186 CHAPTER 8 API functions

8.2.1 OS_MAILBOX_Clear()

Description

Clears all messages in the specified mailbox.

Prototype

void OS_MAILBOX_Clear(OS_MAILBOX* pMB);

Parameters

Parameter Description

pMB Pointer to the mailbox.

Additional information

When the mailbox is in use, a debug build of embOS will call OS_Error() with error code

OS_ERR_MB_INUSE.

OS_MAILBOX_Clear() may cause a task switch.

Example

static OS_MAILBOX _MBKey;

void ClearKeyBuffer(void) {

OS_MAILBOX_Clear(&_MBKey);

}

187 CHAPTER 8 API functions

8.2.2 OS_MAILBOX_Create()

Description

Creates a new mailbox.

Prototype

void OS_MAILBOX_Create(OS_MAILBOX* pMB,

OS_U16 sizeofMsg,

OS_UINT maxnofMsg,

void* Buffer);

Parameters

Parameter Description

pMB Pointer to the mailbox.

sizeofMsg Size of a message in bytes. Valid values are

1 ≤ sizeofMsg ≤ 32,767.

maxnofMsg Maximum number of messages. Valid values are

1 ≤ MaxnofMsg ≤ 32,767 on 8 or 16bit CPUs, or

1 ≤ MaxnofMsg ≤ 2,147,483,647 on 32bit CPUs.

Buffer Pointer to a memory area used as buffer. The buffer must

be big enough to hold the given number of messages of the

specified size: sizeofMsg * maxnoMsg bytes.

Example

Mailbox used as keayboard buffer:

static OS_MAILBOX _MBKey;

char MBKeyBuffer[6];

void InitKeyMan(void) {

// Create mailbox, functioning as type ahead buffer

OS_MAILBOX_Create(&_MBKey, 1, sizeof(MBKeyBuffer), &MBKeyBuffer);

}

Mailbox used for transferring complex commands from one task to another:

* Example of mailbox used for transferring commands to a task

* that controls a motor

typedef struct {

char Cmd;

int Speed[2];

int Position[2];

} MOTORCMD;

OS_MAILBOX MBMotor;

#define NUM_MOTORCMDS 4

char BufferMotor[sizeof(MOTORCMD) * NUM_MOTORCMDS];

void MOTOR_Init(void) {

/* Create mailbox that holds commands messages */

OS_MAILBOX_Create(&MBMotor, sizeof(MOTORCMD), NUM_MOTORCMDS, &BufferMotor);

}

188 CHAPTER 8 API functions

8.2.3 OS_MAILBOX_Delete()

Description

Deletes a specified mailbox.

Prototype

void OS_MAILBOX_Delete(OS_MAILBOX* pMB);

Parameters

Parameter Description

pMB Pointer to the mailbox.

Additional information

To keep the system fully dynamic, it is essential that mailboxes can be created dynamically.

This also means there must be a way to delete a mailbox when it is no longer needed. The

memory that has been used by the mailbox for the control structure and the buffer can

then be reused or reallocated.

It is the programmer’s responsibility to:

• make sure that the program no longer uses the mailbox to be deleted

• make sure that the mailbox to be deleted actually exists (i.e. has been created first).

When the mailbox is in use, a debug build of embOS will call OS_Error() with error code

OS_ERR_MB_INUSE.

In a debug build OS_Error() will also be called if OS_MAILBOX_Delete() is called while

tasks are waiting for new data from the mailbox. The error code in this case is OS_ER-

R_MAILBOX_DELETE.

Example

static OS_MAILBOX _MBSerIn;

void Cleanup(void) {

OS_MAILBOX_Delete(&_MBSerIn);

}

189 CHAPTER 8 API functions

8.2.4 OS_MAILBOX_Get()

Description

Retrieves a new message of a predefined size from a mailbox if a message is available.

Prototype

char OS_MAILBOX_Get(OS_MAILBOX* pMB,

void* pDest);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pDest

Pointer to the memory area that the message should be

stored at. Make sure that it points to a valid memory area

and that there is sufficient space for an entire message. The

message size (in bytes) was defined when the mailbox was

created.

Return value

0 Success; message retrieved.

1 Message could not be retrieved (mailbox is empty); destination remains un-

changed.

Additional information

If the mailbox is empty, no message is retrieved and pDest remains unchanged, but the

program execution continues. This function never suspends the calling task. It may there-

fore also be called from an interrupt routine.

Example

static OS_MAILBOX _MBData;

struct Data Buffer;

char GetData(void) {

return OS_MAILBOX_Get(&_MBData, &Buffer);

}

190 CHAPTER 8 API functions

8.2.5 OS_MAILBOX_Get1()

Description

Retrieves a new message of size 1 from a mailbox if a message is available.

Prototype

char OS_MAILBOX_Get1(OS_MAILBOX* pMB,

char* pDest);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pDest

Pointer to the memory area that the message should be

stored at. Make sure that it points to a valid memory area

and that there is sufficient space for an entire message. The

message size (in bytes) was defined when the mailbox was

created.

Return value

0 Success; message retrieved.

1 Message could not be retrieved (mailbox is empty); destination remains un-

changed.

Additional information

If the mailbox is empty, no message is retrieved and pDest remains unchanged, but the

program execution continues. This function never suspends the calling task. It may there-

fore also be called from an interrupt routine.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Get()

and OS_MAILBOX_Get1().

Example

static OS_MAILBOX _MBKey;

// If a key has been pressed, it is taken out of the mailbox

// and returned to caller. Otherwise zero is returned.

char GetKey(void) {

char c = 0;

OS_MAILBOX_Get1(&_MBKey, &c);

return c;

}

191 CHAPTER 8 API functions

8.2.6 OS_MAILBOX_GetBlocked()

Description

Retrieves a new message of a predefined size from a mailbox.

Prototype

void OS_MAILBOX_GetBlocked(OS_MAILBOX* pMB,

void* pDest);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pDest

Pointer to the memory area that the message should be

stored at. Make sure that it points to a valid memory area

and that there is sufficient space for an entire message. The

message size (in bytes) was defined when the mailbox was

created.

Additional information

If the mailbox is empty, the task is suspended until the mailbox receives a new message.

Because this routine might require a suspension, it must not be called from an interrupt

routine. Use OS_MAILBOX_Get()/OS_MAILBOX_Get1() instead if you need to retrieve data

from a mailbox from within an ISR.

Example

static OS_MAILBOX _MBData;

struct Data Buffer;

void WaitData(void) {

OS_MAILBOX_GetBlocked(&_MBData, &Buffer);

}

192 CHAPTER 8 API functions

8.2.7 OS_MAILBOX_GetBlocked1()

Description

Retrieves a new message of size 1 from a mailbox.

Prototype

void OS_MAILBOX_GetBlocked1(OS_MAILBOX* pMB,

char* pDest);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pDest

Pointer to the memory area that the message should be

stored at. Make sure that it points to a valid memory area

and that there is sufficient space for an entire message. The

message size (in bytes) was defined when the mailbox was

created.

Additional information

If the mailbox is empty, the task is suspended until the mailbox receives a new message.

Because this routine might require a suspension, it must not be called from an interrupt

routine. Use OS_MAILBOX_Get()/OS_MAILBOX_Get1() instead if you need to retrieve data

from a mailbox from within an ISR.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Get-

Blocked() and OS_MAILBOX_GetBlocked1().

Example

static OS_MAILBOX _MBKey;

char WaitKey(void) {

char c;

OS_MAILBOX_GetBlocked1(&_MBKey, &c);

return c;

}

193 CHAPTER 8 API functions

8.2.8 OS_MAILBOX_GetMessageCnt()

Description

Returns the number of messages currently available in a specified mailbox.

Prototype

OS_UINT OS_MAILBOX_GetMessageCnt(OS_CONST_PTR OS_MAILBOX *pMB);

Parameters

Parameter Description

pMB Pointer to the mailbox.

Return value

The number of messages currently available in the mailbox.

Example

static OS_MAILBOX _MBData;

void PrintAvailableMessages() {

OS_UINT NumOfMsgs;

NumOfMsgs = OS_MAILBOX_GetMessageCnt(&_MBData);

printf("Mailbox contains %d messages.\n", NumOfMsgs);

}

194 CHAPTER 8 API functions

8.2.9 OS_MAILBOX_GetTimed()

Description

Retrieves a new message of a predefined size from a mailbox if a message is available

within a given time.

Prototype

char OS_MAILBOX_GetTimed(OS_MAILBOX* pMB,

void* pDest,

OS_TIME Timeout);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pDest

Pointer to the memory area that the message should be

stored at. Make sure that it points to a valid memory area

and that there is sufficient space for an entire message. The

message size (in bytes) was defined when the mailbox was

created.

Timeout

Maximum time until the requested mail must be available.

Timer period in embOS system ticks. The data type OS_TIME

is defined as an integer, therefore valid values are:

1 ≤ Timeout ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Timeout ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success; message retrieved.

1 Message could not be retrieved (mailbox is empty); destination remains un-

changed.

Additional information

If the mailbox is empty, no message is retrieved, pDest remains unchanged and the task

is suspended for the given timeout. The task continues execution according to the rules of

the scheduler as soon as a mail is available within the given timeout, or after the timeout

value has expired.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that mail becomes available after the timeout expired, but before the

calling task is resumed. Anyhow, the function returns with timeout, because the mail was

not available within the requested time. In this case, no mail is retrieved from the mailbox.

Example

static OS_MAILBOX _MBData;

struct Data Buffer;

char GetData(void) {

return OS_MAILBOX_GetTimed(&_MBData, &Buffer, 10); // Wait for 10 system ticks

}

195 CHAPTER 8 API functions

8.2.10 OS_MAILBOX_GetTimed1()

Description

Retrieves a new message of size 1 from a mailbox if a message is available within a given

time.

Prototype

char OS_MAILBOX_GetTimed1(OS_MAILBOX* pMB,

char* pDest,

OS_TIME Timeout);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pDest

Pointer to the memory area that the message should be

stored at. Make sure that it points to a valid memory area

and that there is sufficient space for an entire message. The

message size (in bytes) was defined when the mailbox was

created.

Timeout

Maximum time until the requested mail must be available.

Timer period in embOS system ticks. The data type OS_TIME

is defined as an integer, therefore valid values are:

1 ≤ Timeout ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Timeout ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success; message retrieved.

1 Message could not be retrieved (mailbox is empty); destination remains un-

changed.

Additional information

If the mailbox is empty, no message is retrieved, pDest remains unchanged and the task

is suspended for the given timeout. The task continues execution according to the rules of

the scheduler as soon as a mail is available within the given timeout, or after the timeout

value has expired.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that mail becomes available after the timeout expired, but before the

calling task is resumed. Anyhow, the function returns with timeout, because the mail was

not available within the requested time. In this case, no mail is retrieved from the mailbox.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Get-

Timed() and OS_MAILBOX_GetTimed1().

Example

static OS_MAILBOX _MBKey;

// If a key has been pressed, it is taken out of the mailbox

// and returned to caller. Otherwise zero is returned.

char GetKey(void) {

char c = 0;

OS_MAILBOX_GetTimed1(&_MBKey, &c, 10); // Wait for 10 system ticks

return c;

}

196 CHAPTER 8 API functions

8.2.11 OS_MAILBOX_GetPtr()

Description

Retrieves a pointer to a new message of a predefined size from a mailbox, if a message

is available. Non blocking function.

Prototype

char OS_MAILBOX_GetPtr(OS_MAILBOX* pMB,

void** ppDest);

Parameters

Parameter Description

pMB Pointer to the mailbox.

ppDest Pointer to the memory area that a pointer to the message

should be stored at. The message size (in bytes) was defined

when the mailbox was created.

Return value

0 Success; message retrieved.

1 Message could not be retrieved (mailbox is empty); destination remains un-

changed.

Additional information

If the mailbox is empty, no message is retrieved and ppDest remains unchanged, but

the program execution continues. This function never suspends the calling task. It may

therefore also be called from an interrupt routine.

The retrieved message is not removed from the mailbox, this must be done by a call

of OS_MAILBOX_Purge() after the message was processed. Only one message can be

processed at a time. As long as the message is not removed from the mailbox, the mail-

box is marked “in use”. Following calls of OS_MAILBOX_Clear(), OS_MAILBOX_Delete(),

OS_MAILBOX_GetBlocked*() and OS_MAILBOX_GetPtrBlocked*() functions are not allowed

until OS_MAILBOX_Purge() is called and will call OS_Error() in debug builds of embOS.

Example

static OS_MAILBOX _MBKey;

void PrintMessage(void) {

char* p;

char r;

r = OS_MAILBOX_GetPtr(&_MBKey, (void**)&p);

if (r == 0) {

printf("%d\n", *p);

OS_MAILBOX_Purge(&_MBKey);

}

197 CHAPTER 8 API functions

8.2.12 OS_MAILBOX_GetPtrBlocked()

Description

Retrieves a pointer to a new message of a predefined size from a mailbox.

Prototype

void OS_MAILBOX_GetPtrBlocked(OS_MAILBOX* pMB,

void** ppDest);

Parameters

Parameter Description

pMB Pointer to the mailbox.

ppDest Pointer to the memory area that a pointer to the message

should be stored at. The message size (in bytes) was defined

when the mailbox was created.

Additional information

If the mailbox is empty, the task is suspended until the mailbox receives a new message.

Because this routine might require a suspension, it must not be called from an interrupt

routine. Use OS_MAILBOX_GetPtr() instead if you need to retrieve data from a mailbox

from within an ISR.

The retrieved message is not removed from the mailbox, this must be done by a call

of OS_MAILBOX_Purge() after the message was processed. Only one message can be

processed at a time. As long as the message is not removed from the mailbox, the mail-

box is marked “in use”. Following calls of OS_MAILBOX_Clear(), OS_MAILBOX_Delete(),

OS_MAILBOX_GetBlocked*() and OS_MAILBOX_GetPtrBlocked*() functions are not allowed

until OS_MAILBOX_Purge() is called and will call OS_Error() in debug builds of embOS.

Example

static OS_MAILBOX _MBKey;

void PrintMessage(void) {

char* p;

OS_MAILBOX_GetPtrBlocked(&_MBKey, (void**)&p);

printf("%d\n", *p);

OS_MAILBOX_Purge(&_MBKey);

}

198 CHAPTER 8 API functions

8.2.13 OS_MAILBOX_Peek()

Description

Peeks a mail from a mailbox without removing the mail. The mail is copied to *pDest if

one was available.

Prototype

char OS_MAILBOX_Peek(OS_CONST_PTR OS_MAILBOX *pMB,

void* pDest);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pDest Pointer to a buffer that should receive the mail.

Return value

0 Success, mail was available and is copied to *pDest.

1 Mail could not be retrieved (mailbox is empty).

Additional information

This function is non-blocking and never suspends the calling task. It may therefore be called

from an interrupt routine.

Example

static OS_MAILBOX _MBData;

struct Data Buffer;

char PeekData(void) {

return OS_MAILBOX_Peek(&_MBData, &Buffer);

}

199 CHAPTER 8 API functions

8.2.14 OS_MAILBOX_Purge()

Description

Deletes the last retrieved message in a mailbox.

Prototype

void OS_MAILBOX_Purge(OS_MAILBOX* pMB);

Parameters

Parameter Description

pMB Pointer to the mailbox.

Additional information

This routine should be called by the task that retrieved the last message from the mailbox,

after the message is processed.

Once a message was retrieved by a call of OS_MAILBOX_GetPtrBlocked() or OS_MAIL-

BOX_GetPtr(), the message must be removed from the mailbox by a call of OS_MAIL-

BOX_Purge() before a following message can be retrieved from the mailbox. Follow-

ing calls of OS_MAILBOX_Clear(), OS_MAILBOX_Delete(), OS_MAILBOX_GetBlocked*() and

OS_MAILBOX_GetPtrBlocked*() functions are not allowed until OS_MAILBOX_Purge() is

called and will call OS_Error() in debug builds of embOS.

Consecutive calls of OS_MAILBOX_Purge() or calling OS_MAILBOX_Purge() without having

retrieved a message from the mailbox will also call OS_Error() in embOS debug builds.

Example

static OS_MAILBOX _MBKey;

void PrintMessage(void) {

char* p;

OS_MAILBOX_GetPtrBlocked(&_MBKey, (void**)&p);

printf("%d\n", *p);

OS_MAILBOX_Purge(&_MBKey);

}

200 CHAPTER 8 API functions

8.2.15 OS_MAILBOX_Put()

Description

Stores a new message of a predefined size in a mailbox if the mailbox is able to accept

one more message.

Prototype

char OS_MAILBOX_Put(OS_MAILBOX* pMB,

OS_CONST_PTR void *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Return value

0 Success; message stored.

1 Message could not be stored (mailbox is full).

Additional information

If the mailbox is full, the message is not stored. This function never suspends the calling

task. It may therefore be called from an interrupt routine.

Example

static OS_MAILBOX _MBData;

void AddMessage(struct Data* pSomeData) {

char Result;

Result = OS_MAILBOX_Put(&_MBData, pSomeData);

if (Result == 1) {

printf("Was not able to add the message to the mailbox.\n");

}

201 CHAPTER 8 API functions

8.2.16 OS_MAILBOX_Put1()

Description

Stores a new message of size 1 in a mailbox if the mailbox is able to accept one more

message.

Prototype

char OS_MAILBOX_Put1(OS_MAILBOX* pMB,

OS_CONST_PTR char *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Return value

0 Success; message stored.

1 Message could not be stored (mailbox is full).

Additional information

If the mailbox is full, the message is not stored. This function never suspends the calling

task. It may therefore be called from an interrupt routine.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Put()

and OS_MAILBOX_Put1().

Example

static OS_MAILBOX _MBKey;

static char _MBKeyBuffer[6];

char KEYMAN_StoreCond(char k) {

return OS_MAILBOX_Put1(&_MBKey, &k); /* Store key if space in buffer */

}

This example can be used with the sample program shown earlier to handle a mailbox as

keyboard buffer.

202 CHAPTER 8 API functions

8.2.17 OS_MAILBOX_PutBlocked()

Description

Stores a new message of a predefined size in a mailbox.

Prototype

void OS_MAILBOX_PutBlocked(OS_MAILBOX* pMB,

OS_CONST_PTR void *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Additional information

If the mailbox is full, the calling task is suspended. Because this routine might require a sus-

pension, it must not be called from an interrupt routine. Use OS_MAILBOX_Put()/OS_MAIL-

BOX_Put1() instead if you need to store data in a mailbox from within an ISR. When using

a debug build of embOS, calling from an interrupt routine will call the error handler OS_Er-

ror() with error code OS_ERR_IN_ISR.

Example

static OS_MAILBOX _MBData;

void AddMessage(struct Data* pSomeData) {

OS_MAILBOX_PutBlocked(&_MBData, pSomeData);

}

203 CHAPTER 8 API functions

8.2.18 OS_MAILBOX_PutBlocked1()

Description

Stores a new message of size 1 in a mailbox.

Prototype

void OS_MAILBOX_PutBlocked1(OS_MAILBOX* pMB,

OS_CONST_PTR char *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Additional information

If the mailbox is full, the calling task is suspended. Because this routine might require a sus-

pension, it must not be called from an interrupt routine. Use OS_MAILBOX_Put()/OS_MAIL-

BOX_Put1() instead if you need to store data in a mailbox from within an ISR. When using

a debug build of embOS, calling from an interrupt routine will call the error handler OS_Er-

ror() with error code OS_ERR_IN_ISR.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Put-

Blocked() and OS_MAILBOX_PutBlocked1().

Example

Single-byte mailbox as keyboard buffer:

static OS_MAILBOX _MBKey;

static char MBKeyBuffer[6];

void KEYMAN_StoreKey(char k) {

OS_MAILBOX_PutBlocked1(&_MBKey, &k); /* Store key, wait if no space in buffer

}

void KEYMAN_Init(void) {

/* Create mailbox functioning as type ahead buffer */

OS_MAILBOX_Create(&_MBKey, 1, sizeof(MBKeyBuffer), &MBKeyBuffer);

}

204 CHAPTER 8 API functions

8.2.19 OS_MAILBOX_PutFront()

Description

Stores a new message of a predefined size into a mailbox in front of all other messages if

the mailbox is able to accept one more message. The new message will be retrieved first.

Prototype

char OS_MAILBOX_PutFront(OS_MAILBOX* pMB,

OS_CONST_PTR void *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Return value

0 Success; message stored.

1 Message could not be stored (mailbox is full).

Additional information

If the mailbox is full, the message is not stored. This function never suspends the calling

task. It may therefore be called from an interrupt routine. This function is useful to store

“emergency” messages into a mailbox which must be handled quickly. It may also be used

in general instead of OS_MAILBOX_Put() to change the FIFO structure of a mailbox into a

LIFO structure.

Example

static OS_MAILBOX _MBData;

void AddMessage(struct Data* pSomeData) {

char Result;

Result = OS_MAILBOX_PutFront(&_MBData, pSomeData);

if (Result == 1) {

printf("Was not able to add the message to the mailbox.\n");

}

205 CHAPTER 8 API functions

8.2.20 OS_MAILBOX_PutFront1()

Description

Stores a new message of size 1 into a mailbox in front of all other messages if the mailbox

is able to accept one more message. The new message will be retrieved first.

Prototype

char OS_MAILBOX_PutFront1(OS_MAILBOX* pMB,

OS_CONST_PTR char *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Return value

0 Success; message stored.

1 Message could not be stored (mailbox is full).

Additional information

If the mailbox is full, the message is not stored. This function never suspends the calling

task. It may therefore be called from an interrupt routine. This function is useful to store

“emergency” messages into a mailbox which must be handled quickly. It may also be used

in general instead of OS_MAILBOX_Put() to change the FIFO structure of a mailbox into a

LIFO structure.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Put-

Front() and OS_MAILBOX_PutFront1().

Example

static OS_MAILBOX _MBData;

void AddMessage(char c) {

char Result;

Result = OS_MAILBOX_PutFront1(&_MBData, &c);

if (Result == 1) {

printf("Was not able to add the message to the mailbox.\n");

}

206 CHAPTER 8 API functions

8.2.21 OS_MAILBOX_PutFrontBlocked()

Description

Stores a new message of a predefined size at the beginning of a mailbox in front of all other

messages. This new message will be retrieved first.

Prototype

void OS_MAILBOX_PutFrontBlocked(OS_MAILBOX* pMB,

OS_CONST_PTR void *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Additional information

If the mailbox is full, the calling task is suspended. Because this routine might require a

suspension, it must not be called from an interrupt routine. Use OS_MAILBOX_PutFront()/

OS_MAILBOX_PutFront1() instead if you need to store data in a mailbox from within an ISR.

This function is useful to store “emergency” messages into a mailbox which must be handled

quickly. It may also be used in general instead of OS_MAILBOX_PutBlocked() to change

the FIFO structure of a mailbox into a LIFO structure.

Example

static OS_MAILBOX _MBData;

void AddMessage(struct Data* pSomeData) {

OS_MAILBOX_PutFrontBlocked(&_MBData, pSomeData);

}

207 CHAPTER 8 API functions

8.2.22 OS_MAILBOX_PutFrontBlocked1()

Description

Stores a new message of size 1 at the beginning of a mailbox in front of all other messages.

This new message will be retrieved first.

Prototype

void OS_MAILBOX_PutFrontBlocked1(OS_MAILBOX* pMB,

OS_CONST_PTR char *pMail);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Additional information

If the mailbox is full, the calling task is suspended. Because this routine might require a

suspension, it must not be called from an interrupt routine. Use OS_MAILBOX_PutFront()/

OS_MAILBOX_PutFront1() instead if you need to store data in a mailbox from within an ISR.

This function is useful to store “emergency” messages into a mailbox which must be handled

quickly. It may also be used in general instead of OS_MAILBOX_PutBlocked() to change

the FIFO structure of a mailbox into a LIFO structure.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Put-

FrontBlocked() and OS_MAILBOX_PutFrontBlocked1().

Example

Single-byte mailbox as keyboard buffer which will follow the LIFO pattern:

static OS_MAILBOX _MBCmd;

static char _MBCmdBuffer[6];

void KEYMAN_StoreCommand(char k) {

OS_MAILBOX_PutFrontBlocked1(&_MBCmd, &k); /* Store command, wait if no space in

buffer*/

}

void KEYMAN_Init(void) {

/* Create mailbox for command buffer */

OS_MAILBOX_Create(&_MBCmd, 1, sizeof(_MBCmdBuffer), &_MBCmdBuffer);

}

208 CHAPTER 8 API functions

8.2.23 OS_MAILBOX_PutTimed()

Description

Stores a new message of a predefined size in a mailbox if the mailbox is able to accept one

more message within a given time. Returns when a new message has been stored in the

mailbox (mailbox not full) or a timeout occurred.

Prototype

OS_BOOL OS_MAILBOX_PutTimed(OS_MAILBOX* pMB,

OS_CONST_PTR void *pMail,

OS_TIME Timeout);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Timeout

Maximum time in embOS system ticks until the given mail

must be stored Timer period in embOS system ticks. The da-

ta type OS_TIME is defined as an integer, therefore valid val-

ues are:

1 ≤ Timeout ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Timeout ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success; message stored.

1 Message could not be stored within the given timeout (mailbox is full). destina-

tion remains unchanged.

Additional information

If the mailbox is full, no message is stored and the task is suspended for the given timeout.

The task continues execution according to the rules of the scheduler as soon as a new mail

is accepted within the given timeout, or after the timeout value has expired.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that the mailbox accepts new messages after the timeout expired,

but before the calling task is resumed. Anyhow, the function returns with timeout, because

the mailbox was not available within the requested time. In this case, no mail is stored

in the mailbox.

Example

static OS_MAILBOX _MBData;

void AddMessage(struct Data* pSomeData) {

OS_MAILBOX_PutTimed(&_MBData, pSomeData, 10); // Wait maximum 10 system ticks

}

209 CHAPTER 8 API functions

8.2.24 OS_MAILBOX_PutTimed1()

Description

Stores a new message of size 1 in a mailbox if the mailbox is able to accept one more

message within a given time. Returns when a new message has been stored in the mailbox

(mailbox not full) or a timeout occurred.

Prototype

OS_BOOL OS_MAILBOX_PutTimed1(OS_MAILBOX* pMB,

OS_CONST_PTR char *pMail,

OS_TIME Timeout);

Parameters

Parameter Description

pMB Pointer to the mailbox.

pMail Pointer to the message to store.

Timeout

Maximum time in embOS system ticks until the given mail

must be stored Timer period in embOS system ticks. The da-

ta type OS_TIME is defined as an integer, therefore valid val-

ues are:

1 ≤ Timeout ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Timeout ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success; message stored.

1 Message could not be stored within the given timeout (mailbox is full). destina-

tion remains unchanged.

Additional information

If the mailbox is full, no message is stored and the task is suspended for the given timeout.

The task continues execution according to the rules of the scheduler as soon as a new mail

is accepted within the given timeout, or after the timeout value has expired.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that the mailbox accepts new messages after the timeout expired,

but before the calling task is resumed. Anyhow, the function returns with timeout, because

the mailbox was not available within the requested time. In this case, no mail is stored

in the mailbox.

See Single-byte mailbox functions on page 182 for differences between OS_MAILBOX_Put-

Timed() and OS_MAILBOX_PutTimed1().

Example

static OS_MAILBOX _MBKey;

void SetKey(char c) {

OS_MAILBOX_PutTimed1(&_MBKey, &c, 10); // Wait maximum 10 system ticks

}

210 CHAPTER 8 API functions

8.2.25 OS_MAILBOX_WaitBlocked()

Description

Waits until a mail is available, but does not retrieve the message from the mailbox.

Prototype

void OS_MAILBOX_WaitBlocked(OS_MAILBOX* pMB);

Parameters

Parameter Description

pMB Pointer to the mailbox.

Additional information

If the mailbox is empty, the task is suspended until a mail is available, otherwise the task

continues. The task continues execution according to the rules of the scheduler as soon as

a mail is available, but the mail is not retrieved from the mailbox.

Example

static OS_MAILBOX _MBData;

void Task(void) {

while (1) {

OS_MAILBOX_WaitBlocked(&_MBData);

...

}

211 CHAPTER 8 API functions

8.2.26 OS_MAILBOX_WaitTimed()

Description

Waits until a mail is available or the timeout has expired, but does not retrieve the message

from the mailbox.

Prototype

char OS_MAILBOX_WaitTimed(OS_MAILBOX* pMB,

OS_TIME Timeout);

Parameters

Parameter Description

pMB Pointer to the mailbox.

Timeout

Maximum time in embOS system ticks until the requested

mail must be available. Timer period in embOS system ticks.

The data type OS_TIME is defined as an integer, therefore

valid values are:

1 ≤ Timeout ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Timeout ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success; message available.

1Timeout; no message available within the given timeout time.

Additional information

If the mailbox is empty, the task is suspended for the given timeout. The task continues

execution according to the rules of the scheduler as soon as a mail is available within the

given timeout, or after the timeout value has expired.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that mail becomes available after the timeout expired, but before the

calling task is resumed. Anyhow, the function returns with timeout, because the mail was

not available within the requested time.

Example

static OS_MAILBOX _MBData;

void Task(void) {

char Result;

Result = OS_MAILBOX_WaitTimed(&_MBData, 10);

if (Result == 0) {

// Compute message

} else {

// Timeout

}

Chapter 9

Queues

213 CHAPTER 9 Introduction

9.1 Introduction

In the preceding chapter, inter-task communication using mailboxes was described. Mail-

boxes can handle small messages with fixed data size only. Queues enable inter-task com-

munication with larger messages or with messages of differing lengths.

A queue consists of a data buffer and a control structure that is managed by the realtime

operating system. The queue behaves like a normal buffer; you can deposit something

(called a message) in the queue and retrieve it later. Queues work as FIFO: first in, first out.

So a message that is deposited first will be retrieved first. There are three major differences

between queues and mailboxes:

1. Queues accept messages of differing lengths. When depositing a message into a queue,

the message size is passed as a parameter.

2. Retrieving a message from the queue does not copy the message, but returns a pointer

to the message and its size. This enhances performance because the data is copied only

when the message is written into the queue.

3. The retrieving function must delete every message after processing it.

4. A new message can only be retrieved from the queue when the previous message was

deleted from the queue.

The queue data buffer contains the messages and some additional management infor-

mation. Each message has a message header containing the message size. The define

OS_Q_SIZEOF_HEADER defines the size of the message header. Additionally, the queue buffer

will be aligned for those CPUs which need data alignment. Therefore the queue data buffer

size must be bigger than the sum of all messages.

Limitations:

Both the number of queues and buffers are limited only by the amount of available memory.

However, the individual message size and the buffer size per queue are limited by software

design.

Message size in bytes on 8 or 16bit CPUs:

1 <= x <= 215 - (1 + OS_Q_SIZEOF_HEADER + MESSAGE_ALIGNMENT)

Message size in bytes on 32bit CPUs:

1 <= x <= 231 - (1 + OS_Q_SIZEOF_HEADER + MESSAGE_ALIGNMENT)

Maximum buffer size in bytes for one queue on 8 or 16bit CPUs:

216 = 0xFFFF

Maximum buffer size in bytes for one queue on 32bit CPUs:

232 = 0xFFFFFFFF

Similar to mailboxes, queues can be used by more than one producer, but must be used

by one consumer only. This means that more than one task or interrupt handler is allowed

to deposit new data into the queue, but it does not make sense to retrieve messages by

multiple tasks.

214 CHAPTER 9 Introduction

Example

#define MESSAGE_ALIGNMENT (4u) // Depends on core/compiler

#define MESSAGES_SIZE_HELLO (7u + OS_Q_SIZEOF_HEADER+ MESSAGE_ALIGNMENT)

#define MESSAGES_SIZE_WORLD (9u + OS_Q_SIZEOF_HEADER+ MESSAGE_ALIGNMENT)

#define QUEUE_SIZE (MESSAGES_SIZE_HELLO + MESSAGES_SIZE_WORLD)

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task-control-blocks

static OS_QUEUE MyQueue;

static char MyQBuffer[QUEUE_SIZE];

static void HPTask(void) {

char* pData;

int Len;

while (1) {

Len = OS_QUEUE_GetPtrBlocked(&MyQueue, (void**)&pData);

OS_TASK_Delay(10);

// Evaluate Message

if (Len) {

OS_COM_SendString(pData);

OS_QUEUE_Purge(&MyQueue);

}

static void LPTask(void) {

while (1) {

OS_QUEUE_Put(&MyQueue, "\nHello\0", 7);

OS_QUEUE_Put(&MyQueue, "\nWorld !\0", 9);

OS_TASK_Delay(500);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_QUEUE_Create(&MyQueue, &MyQBuffer, sizeof(MyQBuffer));

OS_COM_SendString("embOS OS_Queue example");

OS_COM_SendString("\n\nDemonstrating message passing\n");

OS_Start(); // Start embOS

return 0;

}

215 CHAPTER 9 API functions

9.2 API functions

Routine Description

main

Task

ISR

Timer

OS_QUEUE_Clear() Clears all messages in the specified queue. ● ● ● ●

OS_QUEUE_Create() Creates and initializes a message queue. ● ● ● ●

OS_QUEUE_Delete() Deletes a specific message queue. ● ● ● ●

OS_QUEUE_GetMessageCnt() Returns the number of messages that are

currently stored in a queue. ●●●●

OS_QUEUE_GetMessageSize() Returns the size of the first message in the

queue. ●●●●

OS_QUEUE_GetPtr() Retrieve the pointer to a message from the

message queue if a message is available. ●●●●

OS_QUEUE_GetPtrBlocked() Retrieve the pointer to a message from the

message queue. ● ●

OS_QUEUE_GetPtrTimed() Retrieve the pointer to a message from the

message queue within a specified time if a

message is available.

● ●

OS_QUEUE_IsInUse() Delivers information whether the queue is

actually in use. ●●●●

OS_QUEUE_PeekPtr() Retrieve the pointer to a message from the

message queue. ●●●●

OS_QUEUE_Purge() Deletes the last retrieved message in a

queue. ●●●●

OS_QUEUE_Put() Stors a new message of given size in a

queue. ●●●●

OS_QUEUE_PutEx()

Stores a new message, of which the dis-

tinct parts are distributed in memory as in-

dicated by a OS_QUEUE_SRCLIST structure,

in a queue.

●●●●

OS_QUEUE_PutBlocked() Stores a new message of given size in a

queue. ●

OS_QUEUE_PutBlockedEx()

Stores a new message, of which the dis-

tinct parts are distributed in memory as in-

dicated by a OS_QUEUE_SRCLIST structure,

in a queue.

●

OS_QUEUE_PutTimed() Stores a new message of given size in a

queue if space is available within a given

time.

● ●

OS_QUEUE_PutTimedEx()

Stores a new message, of which the dis-

tinct parts are distributed in memory as in-

dicated by a OS_QUEUE_SRCLIST structure,

in a queue.

● ●

216 CHAPTER 9 API functions

9.2.1 OS_QUEUE_Clear()

Description

Clears all messages in the specified queue.

Prototype

void OS_QUEUE_Clear(OS_QUEUE* pQ);

Parameters

Parameter Description

pQ Pointer to the queue.

Additional information

When the queue is in use, a debug build of embOS will call OS_Error() with error code

OS_ERR_QUEUE_INUSE.

OS_QUEUE_Clear() may cause a task switch.

Example

static OS_QUEUE _Queue;

void ClearQueue() {

OS_QUEUE_Clear(&_Queue);

}

217 CHAPTER 9 API functions

9.2.2 OS_QUEUE_Create()

Description

Creates and initializes a message queue.

Prototype

void OS_QUEUE_Create(OS_QUEUE* pQ,

void* pData,

OS_UINT Size);

Parameters

Parameter Description

pQ Pointer to a data structure of type OS_QUEUE reserved for the

management of the message queue.

pData Pointer to a memory area used as data buffer for the queue.

Size Size in bytes of the data buffer.

Additional information

The define OS_Q_SIZEOF_HEADER can be used to calculate the additional management in-

formation bytes needed for each message in the queue data buffer. But it does not account

for the additional space needed for data alignment. Thus the number of messages that can

actually be stored in the queue buffer depends on the message sizes.

Example

#define MESSAGE_CNT 100

#define MESSAGE_SIZE 100

#define MEMORY_QSIZE (MESSAGE_CNT * (MESSAGE_SIZE + OS_Q_SIZEOF_HEADER))

static OS_QUEUE _MemoryQ;

static char _acMemQBuffer[MEMORY_QSIZE];

void MEMORY_Init(void) {

OS_QUEUE_Create(&_MemoryQ, &_acMemQBuffer, sizeof(_acMemQBuffer));

}

218 CHAPTER 9 API functions

9.2.3 OS_QUEUE_Delete()

Description

Deletes a specific message queue.

Prototype

void OS_QUEUE_Delete(OS_QUEUE* pQ);

Parameters

Parameter Description

pQ Pointer to the queue.

Additional information

To keep the system fully dynamic, it is essential that queues can be created dynamically.

This also means there must be a way to delete a queue when it is no longer needed. The

memory that has been used by the queue for the control structure and the buffer can then

be reused or reallocated.

It is the programmer’s responsibility to:

• make sure that the program no longer uses the queue to be deleted

• make sure that the queue to be deleted actually exists (i.e. has been created first).

When the queue is in use, a debug build of embOS will call OS_Error() with error code

OS_ERR_QUEUE_INUSE.

When tasks are waiting, a debug build of embOS will call OS_Error() with error code

OS_ERR_QUEUE_DELETE is called.

Example

static OS_QUEUE _QSerIn;

void Cleanup(void) {

OS_QUEUE_Delete(&_QSerIn);

}

219 CHAPTER 9 API functions

9.2.4 OS_QUEUE_GetMessageCnt()

Description

Returns the number of messages that are currently stored in a queue.

Prototype

int OS_QUEUE_GetMessageCnt(OS_CONST_PTR OS_QUEUE *pQ);

Parameters

Parameter Description

pQ Pointer to the queue.

Return value

The number of messages in the queue.

Example

static OS_QUEUE _Queue;

void PrintNumberOfMessages() {

int Cnt;

Cnt = OS_QUEUE_GetMessageCnt(&_Queue);

printf("%d messages available.\n", Cnt);

}

220 CHAPTER 9 API functions

9.2.5 OS_QUEUE_GetMessageSize()

Description

Returns the size of the first message in the queue.

Prototype

int OS_QUEUE_GetMessageSize(OS_CONST_PTR OS_QUEUE *pQ);

Parameters

Parameter Description

pQ Pointer to the queue.

Return value

= 0 No data available.

> 0 Size of message in bytes.

Additional information

If the queue is empty OS_QUEUE_GetMessageSize() returns zero. If a message is avail-

able OS_QUEUE_GetMessageSize() returns the size of that message. The message is not

retrieved from the queue.

Example

static OS_QUEUE _MemoryQ;

static void _MemoryTask(void) {

int Len;

while (1) {

Len = OS_QUEUE_GetMessageSize(&_MemoryQ); // Get message length

if (Len > 0) {

printf("Message with size %d retrieved\n", Len);

OS_QUEUE_Purge(&_MemoryQ); // Delete message

}

OS_TASK_Delay(10);

}

221 CHAPTER 9 API functions

9.2.6 OS_QUEUE_GetPtr()

Description

Retrieve the pointer to a message from the message queue if a message is available.

Prototype

int OS_QUEUE_GetPtr(OS_QUEUE* pQ,

void** ppData);

Parameters

Parameter Description

pQ Pointer to the queue.

ppData Address of the pointer which will be set to the addr. of the

message.

Return value

= 0 No message available in queue.

> 0 Size of the message that was retrieved from the queue.

Additional information

If the queue is empty, the function returns zero and the value of ppData is undefined.

This function never suspends the calling task. It may therefore be called from an interrupt

routine or timer. If a message could be retrieved it is not removed from the queue, this

must be done by a call of OS_QUEUE_Purge() after the message was processed. Only one

message can be processed at a time. As long as the message is not removed from the

queue, the queue is marked “in use”.

Following calls of OS_QUEUE_Clear(), OS_QUEUE_Delete(), OS_QUEUE_GetPtr(),

OS_QUEUE_GetPtrBlocked() and OS_QUEUE_GetPtrTimed() functions are not allowed until

OS_QUEUE_Purge() is called and will call OS_Error() in debug builds of embOS.

Example

static OS_QUEUE _MemoryQ;

static void _MemoryTask(void) {

int Len;

char* pData;

while (1) {

Len = OS_QUEUE_GetPtr(&_MemoryQ, &pData); // Check message

if (Len > 0) {

Memory_WritePacket(*(U32*)pData, Len); // Process message

OS_QUEUE_Purge(&_MemoryQ); // Delete message

} else {

DoSomethingElse();

}

222 CHAPTER 9 API functions

9.2.7 OS_QUEUE_GetPtrBlocked()

Description

Retrieve the pointer to a message from the message queue.

Prototype

int OS_QUEUE_GetPtrBlocked(OS_QUEUE* pQ,

void** ppData);

Parameters

Parameter Description

pQ Pointer to the queue.

ppData Addr. of the pointer which will be set to the addr. of the

message.

Return value

Size of the message in bytes.

Additional information

If the queue is empty, the calling task is suspended until the queue receives a new message.

Because this routine might require a suspension, it must not be called from an interrupt

routine or timer. Use OS_GetPtrCond() instead. The retrieved message is not removed

from the queue, this must be done by a call of OS_QUEUE_Purge() after the message was

processed. Only one message can be processed at a time. As long as the message is not

removed from the queue, the queue is marked “in use”.

Following calls of OS_QUEUE_Clear(), OS_QUEUE_Delete(), OS_QUEUE_GetPtr(),

OS_QUEUE_GetPtrBlocked() and OS_QUEUE_GetPtrTimed() functions are not allowed until

OS_QUEUE_Purge() is called and will call OS_Error() in debug builds of embOS.

Example

static OS_QUEUE _MemoryQ;

static void _MemoryTask(void) {

int Len;

char* pData;

while (1) {

Len = OS_QUEUE_GetPtrBlocked(&_MemoryQ, &pData); // Get message

Memory_WritePacket(*(U32*)pData, Len); // Process message

OS_QUEUE_Purge(&_MemoryQ); // Delete message

}

223 CHAPTER 9 API functions

9.2.8 OS_QUEUE_GetPtrTimed()

Description

Retrieve the pointer to a message from the message queue within a specified time if a

message is available.

Prototype

int OS_QUEUE_GetPtrTimed(OS_QUEUE* pQ,

void** ppData,

OS_TIME Timeout);

Parameters

Parameter Description

pQ Pointer to the queue.

ppData Address of the pointer which will be set to the addr. of the

message.

Timeout

Maximum time until the requested message must be avail-

able. Timer period in embOS system ticks. The data type

OS_TIME is defined as an integer, therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

= 0 No message available in queue.

> 0 Size of the message that was retrieved from the queue.

Sets the pointer ppData to the message that should be retrieved.

Additional information

If the queue is empty no message is retrieved, the task is suspended for the given timeout

and the value of ppData is undefined. The task continues execution according to the rules

of the scheduler as soon as a message is available within the given timeout, or after the

timeout value has expired.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that a message becomes available after the timeout expired, but

before the calling task is resumed. Anyhow, the function returns with timeout, because the

message was not available within the requested time. In this case the state of the queue is

not modified by OS_QUEUE_GetPtrTimed() and a pointer to the message is not delivered.

As long as a message was retrieved and the message is not removed from the queue, the

queue is marked “in use”.

Following calls of OS_QUEUE_Clear(), OS_QUEUE_Delete(), OS_QUEUE_GetPtr(),

OS_QUEUE_GetPtrBlocked() and OS_QUEUE_GetPtrTimed() functions are not allowed until

OS_QUEUE_Purge() is called and will call OS_Error() in debug builds of embOS.

Example

static OS_QUEUE _MemoryQ;

static void _MemoryTask(void) {

int Len;

char* pData;

while (1) {

Len = OS_QUEUE_GetPtrTimed(&_MemoryQ, &pData, 10); // Check message

if (Len > 0) {

Memory_WritePacket(*(U32*)pData, Len); // Process message

224 CHAPTER 9 API functions

OS_QUEUE_Purge(&_MemoryQ); // Delete message

} else { // Timeout

DoSomethingElse();

}

225 CHAPTER 9 API functions

9.2.9 OS_QUEUE_IsInUse()

Description

Delivers information whether the queue is actually in use.

Prototype

OS_BOOL OS_QUEUE_IsInUse(OS_CONST_PTR OS_QUEUE *pQ);

Parameters

Parameter Description

pQ Pointer to the queue.

Return value

= 0 Queue is not in use.

≠ 0 Queue is in use and may not be deleted or cleared.

Additional information

A queue must not be cleared or deleted when it is in use. In use means a task or function

actually accesses the queue and holds a pointer to a message in the queue.

OS_QUEUE_IsInUse() can be used to examine the state of the queue before it can be cleared

or deleted, as these functions must not be performed as long as the queue is used.

Example

void DeleteQ(OS_QUEUE* pQ) {

OS_INT_IncDI(); // Avoid state change of the queue by task or interrupt

// Wait until queue is not used

while (OS_QUEUE_IsInUse(pQ) != 0) {

OS_TASK_Delay(1);

}

OS_QUEUE_Delete(pQ);

OS_INT_DecRI();

}

226 CHAPTER 9 API functions

9.2.10 OS_QUEUE_PeekPtr()

Description

Retrieve the pointer to a message from the message queue. The message must not be

purged.

Prototype

int OS_QUEUE_PeekPtr(OS_CONST_PTR OS_QUEUE *pQ,

void** ppData);

Parameters

Parameter Description

pQ Pointer to the queue.

ppData Address of the pointer which will be set to the address of the

message.

Return value

= 0 No message available.

≠ 0 Size of message in bytes.

Sets the pointer ppData to the message that should be retrieved.

Additional information

Note

Ensure the queues state is not altered as long as a message is processed. That is the

reason for calling OS_INT_IncDI() in the sample. Ensure no cooperative task switch is

performed, as this may also alter the queue state and buffer. OS_TASK_EnterRegion()

does not inhibit cooperative task switches!

Example

static OS_QUEUE _MemoryQ;

static void _MemoryTask(void) {

int Len;

char* pData;

while (1) {

OS_INT_IncDI();

// Avoid state changes of the queue by task or interrupt

Len = OS_QUEUE_PeekPtr(&_MemoryQ, &pData); // Get message

if (Len > 0) {

Memory_WritePacket(*(U32*)pData, Len); // Process message

}

OS_INT_DecRI();

}

227 CHAPTER 9 API functions

9.2.11 OS_QUEUE_Purge()

Description

Deletes the last retrieved message in a queue.

Prototype

void OS_QUEUE_Purge(OS_QUEUE* pQ);

Parameters

Parameter Description

pQ Pointer to the queue.

Additional information

This routine should be called by the task that retrieved the last message from the queue,

after the message is processed.

Once a message was retrieved by a call of OS_QUEUE_GetPtrBlocked(), OS_QUEUE_GetP-

tr() or OS_QUEUE_GetPtrTimed(), the message must be removed from the queue by a

call of OS_QUEUE_Purge() before a following message can be retrieved from the queue.

Consecutive calls of OS_QUEUE_Purge() or calling OS_QUEUE_Purge() without having re-

trieved a message from the queue will call the embOS error handler OS_Error() in embOS

debug builds.

Example

static OS_QUEUE _MemoryQ;

static void _MemoryTask(void) {

int Len;

char* pData;

while (1) {

Len = OS_QUEUE_GetPtrBlocked(&_MemoryQ, &pData); // Get message

Memory_WritePacket(*(U32*)pData, Len); // Process message

OS_QUEUE_Purge(&_MemoryQ); // Delete message

}

228 CHAPTER 9 API functions

9.2.12 OS_QUEUE_Put()

Description

Stors a new message of given size in a queue.

Prototype

int OS_QUEUE_Put(OS_QUEUE* pQ,

OS_CONST_PTR void *pSrc,

OS_UINT Size);

Parameters

Parameter Description

pQ Pointer to a data structure of type OS_QUEUE.

pSrc Pointer to the message to store.

Size Size of the message to store. Valid values are:

1 ≤ Size ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Size ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success, message stored.

1 Message could not be stored (queue is full).

Additional information

This routine never suspends the calling task and may therefore be called from an interrupt

routine.

When the message is deposited into the queue, the entire message is copied into the queue

buffer, not only the pointer to the data. Therefore the message content is protected and

remains valid until it is retrieved and accessed by a task reading the message.

Example

static OS_QUEUE _MemoryQ;

int MEMORY_Write(const char* pData, OS_UINT Len) {

return OS_QUEUE_Put(&_MemoryQ, pData, Len);

}

229 CHAPTER 9 API functions

9.2.13 OS_QUEUE_PutEx()

Description

Stores a new message, of which the distinct parts are distributed in memory as indicated

by a OS_QUEUE_SRCLIST structure, in a queue.

Prototype

int OS_QUEUE_PutEx(OS_QUEUE* pQ,

OS_CONST_PTR OS_QUEUE_SRCLIST *pSrcList,

OS_UINT NumSrc);

Parameters

Parameter Description

pQ Pointer to the queue.

pSrcList Pointer to an array of OS_QUEUE_SRCLIST structures which

contain pointers to the data to store.

NumSrc Number of OS_QUEUE_SRCLIST structures at pSrcList.

Return value

0 Success, message stored.

1 Message could not be stored (queue is full).

Additional information

This routine never suspends the calling task and may therefore be called from main(), an

interrupt routine or a software timer.

When the message is deposited into the queue, the entire message is copied into the queue

buffer, not only the pointer(s) to the data. Therefore the message content is protected and

remains valid until it is retrieved and accessed by a task reading the message.

Example

OS_CONST_PTR OS_QUEUE_SRCLIST aDataList[] = { {"Hello ", 6},

{"World!", 6}

};

OS_QUEUE_PutEx(&_MemoryQ, aDataList, 2);

9.2.13.1 The OS_QUEUE_SRCLIST structure

The OS_QUEUE_SRCLIST structure consists of two elements:

Parameter Description

pSrc Pointer to a part of the message to store.

Size

Size of the part of the message. Valid values are:

1 ≤ Size ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Size ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Note

The total size of all parts of the message must not exceed 0x7FFF on 8/16 bit CPUs,

or 0x7FFFFFFF on 32 bit CPUs, respectively.

230 CHAPTER 9 API functions

9.2.14 OS_QUEUE_PutBlocked()

Description

Stores a new message of given size in a queue.

Prototype

void OS_QUEUE_PutBlocked(OS_QUEUE* pQ,

OS_CONST_PTR void *pSrc,

OS_UINT Size);

Parameters

Parameter Description

pQ Pointer to the queue.

pSrc Pointer to the message to store.

Size Size of the message to store. Valid values are:

1 ≤ Size ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Size ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Additional information

If the queue is full, the calling task is suspended.

When the message is deposited into the queue, the entire message is copied into the queue

buffer, not only the pointer(s) to the data. Therefore the message content is protected and

remains valid until it is retrieved and accessed by a task reading the message.

Example

static OS_QUEUE _MemoryQ;

void StoreMessage(const char* pData, OS_UINT Len)

OS_QUEUE_PutBlocked(&_MemoryQ, pData, Len);

}

231 CHAPTER 9 API functions

9.2.15 OS_QUEUE_PutBlockedEx()

Description

Stores a new message, of which the distinct parts are distributed in memory as indicated

by a OS_QUEUE_SRCLIST structure, in a queue. Blocks the calling task when queue is full.

Prototype

void OS_QUEUE_PutBlockedEx(OS_QUEUE* pQ,

OS_CONST_PTR OS_QUEUE_SRCLIST *pSrcList,

OS_UINT NumSrc);

Parameters

Parameter Description

pQ Pointer to the queue.

pSrcList Pointer to an array of OS_QUEUE_SRCLIST structures which

contain pointers to the data to store.

NumSrc Number of OS_QUEUE_SRCLIST structures at pSrcList.

Additional information

If the queue is full, the calling task is suspended.

When the message is deposited into the queue, the entire message is copied into the queue

buffer, not only the pointer(s) to the data. Therefore the message content is protected and

remains valid until it is retrieved and accessed by a task reading the message.

For more information on the OS_QUEUE_SRCLIST structure, refer to The OS_QUEUE_SRCLIST

structure in the chapter The OS_QUEUE_SRCLIST structure on page 229.

Example

OS_CONST_PTR OS_QUEUE_SRCLIST aDataList[] = { {"Hello ", 6},

{"World!", 6}

};

OS_QUEUE_PutEx(&_MemoryQ, aDataList, 2);

232 CHAPTER 9 API functions

9.2.16 OS_QUEUE_PutTimed()

Description

Stores a new message of given size in a queue if space is available within a given time.

Prototype

char OS_QUEUE_PutTimed(OS_QUEUE* pQ,

OS_CONST_PTR void *pSrc,

OS_UINT Size,

OS_TIME Timeout);

Parameters

Parameter Description

pQ Pointer to the queue.

pSrc Pointer to the message to store.

Size Size of the message to store. Valid values are:

1 ≤ Size ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ Size ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Timeout

Maximum time until the given message must be stored.

Timer period in embOS system ticks. The data type OS_TIME

is defined as an integer, therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

0 Success, message stored.

1 Message could not be stored within the specified time (insufficient space).

Additional information

If the queue holds insufficient space, the calling task is suspended until space for the mes-

sage is available, or the specified timeout time has expired. If the message could be de-

posited into the queue within the sepcified time, the function returns zero.

When the message is deposited into the queue, the entire message is copied into the queue

buffer, not only the pointer(s) to the data. Therefore the message content is protected and

remains valid until it is retrieved and accessed by a task reading the message.

Example

static OS_QUEUE _MemoryQ;

int MEMORY_WriteTimed(const char* pData, OS_UINT Len, OS_TIME Timeout) {

return OS_QUEUE_PutTimed(&_MemoryQ, pData, Len, Timeout);

}

233 CHAPTER 9 API functions

9.2.17 OS_QUEUE_PutTimedEx()

Description

Stores a new message, of which the distinct parts are distributed in memory as indicated by

a OS_QUEUE_SRCLIST structure, in a queue. Suspends the calling task for a given timeout

when the queue is full.

Prototype

char OS_QUEUE_PutTimedEx(OS_QUEUE* pQ,

OS_CONST_PTR OS_QUEUE_SRCLIST *pSrcList,

OS_UINT NumSrc,

OS_TIME Timeout);

Parameters

Parameter Description

pQ Pointer to the queue.

pSrcList Pointer to an array of OS_QUEUE_SRCLIST structures which

contain pointers to the data to store.

NumSrc Number of OS_QUEUE_SRCLIST structures at pSrcList.

Timeout

Maximum time until the given message must be stored.

Timer period in embOS system ticks. The data type OS_TIME

is defined as an integer, therefore valid values are:

1 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

1 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

= 0 Success, message stored.

≠ 0 Message could not be stored within the specified time (insufficient space).

Additional information

If the queue holds insufficient space, the calling task is suspended until space for the mes-

sage is available or the specified timeout time has expired. If the message could be de-

posited into the queue within the sepcified time, the function returns zero.

When the message is deposited into the queue, the entire message is copied into the queue

buffer, not only the pointer(s) to the data. Therefore the message content is protected and

remains valid until it is retrieved and accessed by a task reading the message.

For more information on the OS_QUEUE_SRCLIST structure, refer to The OS_QUEUE_SRCLIST

structure in the chapter The OS_QUEUE_SRCLIST structure on page 229.

Example

OS_CONST_PTR OS_QUEUE_SRCLIST aDataList[] = { {"Hello ", 6},

{"World!", 6}

};

OS_QUEUE_PutEx(&MemoryQ, aDataList, 2, 100);

Chapter 10

Watchdog

235 CHAPTER 10 Introduction

10.1 Introduction

A watchdog timer is a hardware timer that is used to reset a microcontroller after a speci-

fied amount of time. During normal operation, the microcontroller application periodically

restarts (“triggers”) the watchdog timer to prevent it from timing out. In case of malfunc-

tion, however, the watchdog timer will eventually time out and subsequently reset the mi-

crocontroller. This allows to detect and recover from microcontroller malfunctions.

For example, in a system without an RTOS, the watchdog timer would be triggered period-

ically from a single point in the application. When the application does not run properly,

the watchdog timer will not be triggered and thus the watchdog will cause a reset of the

microcontroller.

In a system that includes an RTOS, on the other hand, multiple tasks run at the same time.

It may happen that one or more of these tasks runs properly, while other tasks fail to run as

intended. Hence it may be insufficient to trigger the watchdog from one of these tasks only.

Therefore, embOS offers a watchdog support module that allows to automatically check if

all tasks, software timers, or even interrupt routines are executing properly.

Example

#include "RTOS.h"

static OS_STACKPTR int StackHP[128], StackLP[128];

static OS_TASK TCBHP, TCBLP;

static OS_WD WatchdogHP, WatchdogLP;

static OS_TICK_HOOK Hook;

static void _TriggerWatchDog(void) {

WD_REG = TRIGGER_WD; // Trigger the hardware watchdog.

}

static void _Reset(OS_CONST_PTR OS_WD* pWD) {

OS_USEPARA(pWD);

// Applications can use pWD to detect WD expiration cause.

SYSTEM_CTRL_REG = PERFORM_RESET; // Reboot microcontroller.

}

static void HPTask(void) {

OS_WD_Add(&WatchdogHP, 50);

while (1) {

OS_TASK_Delay(50);

OS_WD_Trigger(&WatchdogHP);

}

static void LPTask(void) {

OS_WD_Add(&WatchdogLP, 200);

while (1) {

OS_TASK_Delay(200);

OS_WD_Trigger(&WatchdogLP);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_WD_Config(&_TriggerWatchDog, &_Reset);

OS_TICK_AddHook(&Hook, OS_WD_Check);

OS_Start(); // Start embOS

return 0;

}

236 CHAPTER 10 API functions

10.2 API functions

Routine Description

main

Task

ISR

Timer

OS_WD_Add() Adds a software watchdog timer to the watchdog list. ● ●

OS_WD_Check() Checks if a watchdog timer expired. ● ● ● ●

OS_WD_Config() Sets the watchdog callback functions. ● ●

OS_WD_Remove() Removes a watchdog timer from the watchdog list. ● ●

OS_WD_Trigger() Triggers a watchdog timer. ● ● ● ●

237 CHAPTER 10 API functions

10.2.1 OS_WD_Add()

Description

Adds a software watchdog timer to the watchdog list.

Prototype

void OS_WD_Add(OS_WD* pWD,

OS_TIME Timeout);

Parameters

Parameter Description

pWD Pointer to a watchdog timer object.

Timeout

Watchdog timer timeout.

Must be within the following range:

0 ≤ t ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs

0 ≤ t ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs

Please note that these are signed values.

Example

static OS_WD _myWD;

void HPTask(void) {

OS_WD_Add(&_myWD, 50);

while (1) {

OS_WD_Trigger(&_myWD);

OS_TASK_Delay(50);

}

238 CHAPTER 10 API functions

10.2.2 OS_WD_Check()

Description

Checks if a watchdog timer expired. If no watchdog timer expired the hardware watchdog

is triggered. If a watchdog timer expired, the callback function is called.

Prototype

void OS_WD_Check(void);

Additional information

OS_WD_Check() must be called periodically. It is good practice to call it from the system

tick handler.

Example

void SysTick_Handler(void) {

OS_INT_Enter();

OS_Tick_Handle();

OS_WD_Check();

OS_INT_Leave();

}

239 CHAPTER 10 API functions

10.2.3 OS_WD_Config()

Description

Sets the watchdog callback functions.

Prototype

void OS_WD_Config(voidRoutine* pfTriggerFunc,

OS_WD_RESET_CALLBACK* pfResetFunc);

Parameters

Parameter Description

pfTriggerFunc Function pointer to hardware watchdog trigger callback func-

tion.

pfResetFunc Function pointer to callback function which is called in case

of an expired watchdog timer. pfResetFunc is optional and

may be NULL.

Additional information

pfResetFunc may be used to perform additional operations inside a callback function prior

to the reset of the microcontroller. For example, a message may be written to a log file. If

pfResetFunc is NULL, no callback function gets executed, but the hardware watchdog will

still cause a reset of the microcontroller.

Example

static void _TriggerWatchDog(void) {

WD_REG = TRIGGER_WD; // Trigger the hardware watchdog

}

static void _Reset(OS_CONST_PTR OS_WD* pWD) {

_WriteLogMessage(pWD);

// Store information about expired watchdog prior to reset.

SYSTEM_CTRL_REG = PERFORM_RESET; // Reboot microcontroller

}

int main(void) {

...

OS_WD_Config(&_TriggerWatchDog, &_Reset);

OS_Start();

}

Note

In previous versions of embOS, OS_WD_Config() expected the parameter pfReset-

Func to be of a different type.

Since embOS V4.40, instead of a callback of the type voidRoutine*, OS_WD_Config()

expects a callback of type OS_WD_RESET_CALLBACK*. This allows for passing the rele-

vant OS_WD structure to the routine, e.g. for further examination by the application.

240 CHAPTER 10 API functions

10.2.4 OS_WD_Remove()

Description

Removes a watchdog timer from the watchdog list.

Prototype

void OS_WD_Remove(OS_CONST_PTR OS_WD *pWD);

Parameters

Parameter Description

pWD Pointer to a watchdog timer object.

Example

int main(void) {

OS_WD_Add(&_myWD);

OS_WD_Remove(&_myWD);

}

241 CHAPTER 10 API functions

10.2.5 OS_WD_Trigger()

Description

Triggers a watchdog timer.

Prototype

void OS_WD_Trigger(OS_WD* pWD);

Parameters

Parameter Description

pWD Pointer to a watchdog timer object.

Additional information

Each software watchdog timer must be triggered periodically. If not, the timeout expires

and OS_WD_Check() will no longer trigger the hardware watchdog timer, but will call the

reset callback function (if any).

Example

static OS_WD _myWD;

static void HPTask(void) {

OS_WD_Add(&_myWD, 50);

while (1) {

OS_TASK_Delay(50);

OS_WD_Trigger(&_myWD);

}

Chapter 11

Multi-core Support

243 CHAPTER 11 Introduction

11.1 Introduction

embOS can be utilized on multi-core processors by running separate embOS instances on

each individual core. For synchronization purposes and in order to exchange data between

the cores, embOS includes a comprehensive spinlock API which can be used to control

access to shared memory, peripherals, etc.

Spinlocks

Spinlocks constitute a general purpose locking mechanism in which any process trying to

acquire the lock is caused to actively wait until the lock becomes available. To do so, the

process trying to acquire the lock remains active and repeatedly checks the availability of

the lock in a loop. Effectively, the process will “spin” until it acquires the lock.

Once acquired by a process, spinlocks are usually held by that process until they are ex-

plicitly released. If held by one process for longer duration, spinlocks may severely impact

the runtime behavior of other processes trying to acquire the same spinlock. Therefore,

spinlocks should be held by one process for short periods of time only.

Usage of spinlocks with embOS

embOS spinlocks are intended for inter-core synchronization and communication. They are

not intended for synchronization of individual tasks running on the same core, on which

semaphores, queues and mailboxes should be used instead.

However, multitasking still has to be taken into consideration when using embOS spinlocks.

Specifically, an embOS task holding a spinlock should not be preempted, for this would

prevent that task from releasing the spinlock as fast as possible, which may in return

impact the runtime behavior of other cores attempting to acquire the spinlock. Declaration

of critical regions therefore is explicitly recommended while holding spinlocks.

embOS spinlocks are usually implemented using hardware instructions specific to one ar-

chitecture, but a portable software implementation is provided in addition. If appropriate

hardware instructions are unavailable for the specific architecture in use, the software im-

plementation is provided exclusively.

Note

It is important to use matching implementations on each core of the multicore proces-

sor that shall access the same spinlock.

For example, a core supporting a hardware implementation may use that implementation

to access a spinlock that is shared with another core that supports the same hardware

implementation. At the same time, that core may use the software implementation to access

a different spinlock that is shared with a different core that does not support the same

hardware implementation. However, in case all three cores in this example should share

the same spinlock, each of them has to use the software implementation.

To know the spinlock’s location in memory, each core’s application must declare the ap-

propriate OS_SPINLOCK variable (or OS_SPINLOCK_SW, respectively) at an identical memory

address. Initialization of the spinlock, however, must be performed by one core only. This

API is not available in embOS library mode OS_LIBMODE_SAFE.

Example of using spinlocks

Two cores of a multi-core processor shall access an hardware peripheral, e.g. a LC display.

To avoid situations in which both cores access the LCD simultaneously, access must be

restricted through usage of a spinlock: Every time the LCD is used by one core, it must first

claim the spinlock through the respective embOS API call. After the LCD has been written

to, the spinlock is released by another embOS API call.

Data exchange between cores can be implemented analogously, e.g. through declaration

of a buffer in shared memory: Here, every time a core shall write data to the buffer, it

must acquire the spinlock first. After the data has been written to the buffer, the spinlock

244 CHAPTER 11 Introduction

is released. This ensures that neither core can interfere with the writing of data by the

other core.

Core 0:

#include "RTOS.h"

static OS_STACKPTR int Stack[128]; // Task stack

static OS_TASK TCB; // Task-control-block

static OS_SPINLOCK MySpinlock @ ".shared_mem";

static void Task(void) {

while (1) {

OS_TASK_EnterRegion(); // Inhibit preemptive task switches

OS_SPINLOCK_Lock(&MySpinlock); // Acquire spinlock

// Perform critical operation

OS_SPINLOCK_Unlock(&MySpinlock); // Release spinlock

OS_TASK_LeaveRegion(); // Re-allow preemptive task switches

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize Hardware for OS

OS_SPINLOCK_Create(&MySpinlock); // Initialize Spinlock

OS_TASK_CREATE(&TCB, "Task", 100, Task, Stack);

OS_Start(); // Start multitasking

return 0;

}

Core 1:

#include "RTOS.h"

static OS_STACKPTR int Stack[128]; // Task stack

static OS_TASK TCB; // Task-control-block

static OS_SPINLOCK MySpinlock @ ".shared_mem";

static void Task(void) {

while (1) {

OS_TASK_EnterRegion(); // Inhibit preemptive task switches

OS_SPINLOCK_Lock(&MySpinlock); // Acquire spinlock

// Perform critical operation

OS_SPINLOCK_Unlock(&MySpinlock); // Release spinlock

OS_TASK_LeaveRegion(); // Re-allow preemptive task switches

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize Hardware for OS

OS_TASK_CREATE(&TCB, "Task", 100, Task, Stack);

OS_Start(); // Start multitasking

return 0;

}

245 CHAPTER 11 API functions

11.2 API functions

Routine Description

main

Task

ISR

Timer

OS_SPINLOCK_Create() Creates a hardware-specific spinlock. ● ●

OS_SPINLOCK_Lock()

Acquires a hardware-specific spinlock. Busy

waiting until the spinlock becomes available.

This function is unavailable for some architec-

tures.

● ●

OS_SPINLOCK_Unlock() Releases a hardware-specific spinlock. ● ●

OS_SPINLOCK_SW_Create() Creates a software-implementation spinlock. ● ●

OS_SPINLOCK_SW_Lock() Acquires a software-implementation spinlock. ● ●

OS_SPINLOCK_SW_Unlock() Releases a software-implementation spinlock. ● ●

246 CHAPTER 11 API functions

11.2.0.1 OS_SPINLOCK_Create()

Description

Creates a hardware-specific spinlock.

This function is unavailable for architectures that do not support an appropriate instruction

set.

Prototype

void OS_SPINLOCK_Create(OS_SPINLOCK* pSpinlock);

Parameters

Parameter Description

pSpinlock Pointer to a variable of type OS_SPINLOCK reserved for the

management of the spinlock. The variable must reside in

shared memory.

Additional information

After creation, the spinlock is not locked.

247 CHAPTER 11 API functions

11.2.0.2 OS_SPINLOCK_Lock()

Description

OS_SPINLOCK_Lock() acquires a hardware-specific spinlock. If the spinlock is unavailable,

the calling task will not be blocked, but will actively wait until the spinlock becomes avail-

able.

This function is unavailable for architectures that do not support an appropriate instruction

set.

Prototype

void OS_SPINLOCK_Lock (OS_SPINLOCK* pSpinlock);

Parameters

Parameter Description

pSpinlock Pointer to a variable of type OS_SPINLOCK reserved for the manage-

ment of the spinlock.

Additional information

A task that has acquired a spinlock must not call OS_SPINLOCK_Lock() for that spinlock

again. The spinlock must first be released by a call to OS_SPINLOCK_Unlock().

The following diagram illustrates how OS_SPINLOCK_Lock() works:

248 CHAPTER 11 API functions

11.2.0.3 OS_SPINLOCK_Unlock()

Description

Releases a hardware-specific spinlock.

This function is unavailable for architectures that do not support an appropriate instruction

set.

Prototype

void OS_SPINLOCK_Unlock(OS_SPINLOCK* pSpinlock);

Parameters

Parameter Description

pSpinlock Pointer to a variable of type OS_SPINLOCK reserved for the

management of the spinlock.

249 CHAPTER 11 API functions

11.2.0.4 OS_SPINLOCK_SW_Create()

Description

Creates a software-implementation spinlock.

Prototype

void OS_SPINLOCK_SW_Create(OS_SPINLOCK_SW* pSpinlock);

Parameters

Parameter Description

pSpinlock Pointer to a data structure of type OS_SPINLOCK_SW reserved

for the management of the spinlock. The variable must re-

side in shared memory.

Additional information

After creation, the spinlock is not locked.

250 CHAPTER 11 API functions

11.2.0.5 OS_SPINLOCK_SW_Lock()

Description

Acquires a software-implementation spinlock. If the spinlock is unavailable, the calling task

will not be blocked, but will actively wait until the spinlock becomes available.

Prototype

void OS_SPINLOCK_SW_Lock(OS_SPINLOCK_SW* pSpinlock,

OS_UINT Id);

Parameters

Parameter Description

pSpinlock Pointer to a data structure of type OS_SPINLOCK_SW reserved

for the management of the spinlock.

Unique identifier to specify the core accessing the spinlock.

Valid values are 0 ≤ Id < OS_SPINLOCK_MAX_CORES. By de-

fault, OS_SPINLOCK_MAX_CORES is defined to 4 and may be

changed when using source code. An embOS debug build

calls OS_Error() in case invalid values are used.

Additional information

A task that has acquired a spinlock must not call OS_SPINLOCK_SW_Lock() for that spinlock

again. The spinlock must first be released by a call to OS_SPINLOCK_SW_Unlock().

OS_SPINLOCK_SW_Lock() implements Lamport’s bakery algorithm, published by Leslie Lam-

port in “Communications of the Association for Computing Machinery”, 1974, Volume 17,

Number 8. An excerpt is publicly available at research.microsoft.com.

The following diagram illustrates how OS_SPINLOCK_SW_Lock() works:

251 CHAPTER 11 API functions

11.2.0.6 OS_SPINLOCK_SW_Unlock()

Description

Releases a software-implementation spinlock.

Prototype

void OS_SPINLOCK_SW_Unlock(OS_SPINLOCK_SW* pSpinlock,

OS_UINT Id);

Parameters

Parameter Description

pSpinlock Pointer to a data structure of type OS_SPINLOCK_SW reserved

for the management of the spinlock.

Unique identifier to specify the core accessing the spinlock.

Valid values are 0 ≤ Id < OS_SPINLOCK_MAX_CORES. By de-

fault, OS_SPINLOCK_MAX_CORES is defined to 4 and may be

changed when using source code. An embOS debug build

calls OS_Error() in case invalid values are used.

Chapter 12

Interrupts

253 CHAPTER 12 What are interrupts?

12.1 What are interrupts?

This chapter explains how to use interrupt service routines (ISRs) in cooperation with em-

bOS. Specific details for your CPU and compiler can be found in the CPU & Compiler Specifics

manual of the embOS documentation.

Interrupts are interruptions of a program caused by hardware. When an interrupt occurs,

the CPU saves its registers and executes a subroutine called an interrupt service routine,

or ISR. After the ISR is completed, the program returns to the highest-priority task in the

READY state. Normal interrupts are maskable. Maskable interrupts can occur at any time

unless they are disabled. ISRs are also nestable – they can be recognized and executed

within other ISRs.

There are several good reasons for using interrupt routines. They can respond very quickly

to external events such as the status change on an input, the expiration of a hardware

timer, reception or completion of transmission of a character via serial interface, or other

types of events. Interrupts effectively allow events to be processed as they occur.

254 CHAPTER 12 Interrupt latency

12.2 Interrupt latency

Interrupt latency is the time between an interrupt request and the execution of the first

instruction of the interrupt service routine. Every computer system has an interrupt latency.

The latency depends on various factors and differs even on the same computer system. The

value that one is typically interested in is the worst case interrupt latency. The interrupt

latency is the sum of a number of individual smaller delays explained below.

Note

Interrupt latency caused by embOS can be avoided entirely when using zero latency

interrupts, which are explained in chapter Zero interrupt latency on page 256.

12.2.1 Causes of interrupt latencies

• The first delay is typically in the hardware: The interrupt request signal needs to be

synchronized to the CPU clock. Depending on the synchronization logic, typically up to

three CPU cycles can be lost before the interrupt request reaches the CPU core.

• The CPU will typically complete the current instruction. This instruction can take

multiple cycles to complete; on most systems, divide, push-multiple, or memory-copy

instructions are the instructions which require most clock cycles. On top of the cycles

required by the CPU, there are in most cases additional cycles required for memory

access. In an ARM7 system, the instruction STMDB SP!,{R0-R11,LR}; typically is the

worst case instruction. It stores thirteen 32 bit registers to the stack, which, in an ARM7

system, takes 15 clock cycles to complete.

• The memory system may require additional cycles for wait states.

• After the current instruction is completed, the CPU performs a mode switch or pushes

registers (typically, PC and flag registers) to the stack. In general, modern CPUs (such

as ARM) perform a mode switch, which requires fewer CPU cycles than saving registers.

• Pipeline fill

Most modern CPUs are pipelined. Execution of an instruction happens in various stages

of the pipeline. An instruction is executed when it has reached its final stage of the

pipeline. Because the mode switch flushes the pipeline, a few extra cycles are required

to refill the pipeline.

12.2.2 Additional causes for interrupt latencies

There can be additional causes for interrupt latencies. These depend on the type of system

used, but we list a few of them.

• Latencies caused by cache line fill. If the memory system has one or multiple caches,

these may not contain the required data. In this case, not only the required data is

loaded from memory, but in a lot of cases a complete line fill needs to be performed,

reading multiple words from memory.

• Latencies caused by cache write back. A cache miss may cause a line to be replaced.

If this line is marked as dirty, it needs to be written back to main memory, causing an

additional delay.

• Latencies caused by MMU translation table walks. Translation table walks can take a

considerable amount of time, especially as they involve potentially slow main memory

accesses. In real-time interrupt handlers, translation table walks caused by the TLB not

containing translations for the handler and/or the data it accesses can increase interrupt

latency significantly.

• Application program. Of course, the application program can cause additional latencies

by disabling interrupts. This can make sense in some situations, but of course causes

additional latencies.

• Interrupt routines. On most systems, one interrupt disables further interrupts. Even if

the interrupts are re-enabled in the ISR, this takes a few instructions, causing additional

latency.

• Real-time Operating system (RTOS). An RTOS also needs to temporarily disable the

interrupts which can call API-functions of the RTOS. Some RTOSes disable all interrupts,

255 CHAPTER 12 Interrupt latency

effectively increasing interrupt latency for all interrupts, some (like embOS) disable only

low-priority interrupts and do thereby not affect the latency of high priority interrupts.

12.2.3 How to measure latency and detect its cause

It is sometimes desirable to detect the cause for high interrupt latency. High interrupt

latency may occur if interrupts are disabled for extended periods of time, or if a low level

interrupt handler is executed before the actual interrupt handler. In these regards, embOS

related functions like OS_INT_Enter() add to interrupt latency as well.

To measure interrupt latency and detect its cause, a timer interrupt may be used. For ex-

ample, if the hardware timer counts upwards starting from zero after each compare-match-

interrupt, its current counter value may be read from within the interrupt service routine

to evaluate how many timer cycles (and thus how much time) have lapsed between the

interrupt’s occurance and the actual execution of the interrupt handler:

static int Latency = 0;

void TimerIntHandler(void) {

OS_INT_Enter();

Latency = TIMER_CNT_VALUE; // Get current timer value

OS_INT_Leave();

}

If this measurement is repeated several times, different results will occur. This is for the

reason that the interrupt will sometimes be asserted while interrupts have been disabled

by the application, while at other times interrupts are enabled when this interrupt request

occurs. Thus, an application may keep track of minimum and maximum latency as shown

below:

static int Latency = 0;

static int MaxLatency = 0;

static int MinLatency = 0xFFFFFFFF;

void TimerIntHandler(void) {

OS_INT_Enter();

Latency = TIMER_CNT_VALUE; // Get current timer value

MinLatency = (Latency < MinLatency) ? Latency : MinLatency;

MaxLatency = (Latency > MaxLatency) ? Latency : MaxLatency;

OS_INT_Leave();

}

Using this method, MinLatency will hold the latency that was caused by hardware (and

any low-level interrupt handler, if applicable). On the other hand, MaxLatency will hold

the latency caused both by hardware and interrupt-masking in software. Therefore, by

substracting MaxLatency - MinLatency, it is possible to calculate the exact latency that

was caused by interrupt-masking (typcially performed by the operating system).

Based on this information, a threshold may be defined to detect the cause of high interrupt

latency. E.g., a breakpoint may be set for when the current timer value exceeds a pre-

defined threshold as shown below:

static int Latency = 0;

void TimerIntHandler(void) {

OS_INT_Enter();

Latency = TIMER_CNT_VALUE; // Get current timer value

if (Latency > LATENCY_THRESHOLD) {

while (1); // Set a breakpoint here

}

OS_INT_Leave();

}

256 CHAPTER 12 Interrupt latency

If code trace information is available upon hitting the breakpoint, the exact cause for the

latency may be checked through a trace log.

Note

If the hardware timer interrupt is the only interrupt in the system, its priority may be

chosen arbitrarily. Otherwise, in case other interrupts occur during measurement as

well, the timer interrupt should be configured to match the specific priority for which

to measure latency. This is important, for other (possibly non-nestable) interrupts

will influence the results depending on their priority relative to the timer interrupt’s

priority, which may or may not be desired on a case-to-case basis.

Also, in order to provide meaningful results, the interrupt should occur quite frequent-

ly. Hence, the timer reload value typically is configured for small periods of time, but

must ensure that interrupt execution will not consume the entire CPU time.

12.2.4 Zero interrupt latency

Zero interrupt latency in the strict sense is not possible as explained above. What we mean

when we say “Zero interrupt latency” is that the latency of high-priority interrupts is not

affected by the RTOS; a system using embOS will have the same worst case interrupt

latency for high priority interrupts as a system running without embOS.

Why is Zero latency important?

In some systems, a maximum interrupt response time or latency can be clearly defined.

This maximum latency can arise from requirements such as maximum reaction time for a

protocol or a software UART implementation that requires very precise timing.

For example a UART receiving at up to 800 kHz in software using ARM FIQ on a 48 MHz

ARM7. This would be impossible to do if FIQ were disabled even for short periods of time.

In many embedded systems, the quality of the product depends on event reaction time

and therefore latency. Typical examples would be systems which periodically read a value

from an A/D converter at high speed, where the accuracy depends on accurate timing. Less

jitter means a better product.

Why can a high priority ISR not use the OS API?

embOS disables low priority interrupts when embOS data structures are modified. During

this time high priority ISR are enabled. If they would call an embOS function, which also

modifies embOS data, the embOS data structures would be corrupted.

How can a high priority ISR communicate with a task?

The most common way is to use global variables, e.g. a periodical read from an ADC and

the result is stored in a global variable.

Another way is to assert an interrupt request for a low priority interrupt from within the high

priority ISR, which may then communicate or wake up one or more tasks. This is helpful

if you want to receive high amounts of data in your high priority ISR. The low priority ISR

may then store the data bytes e.g. in a message queue or in a mailbox.

12.2.5 High / low priority interrupts

Most CPUs support interrupts with different priorities. Different priorities have two effects:

• If different interrupts occur simultaneously, the interrupt with higher priority takes

precedence and its ISR is executed first.

• Interrupts can never be interrupted by other interrupts of the same or lower priority.

The number of interrupt levels depends on the CPU and the interrupt controller. Details

are explained in the CPU/MCU/SoC manuals and the CPU & Compiler Specifics manual of

embOS. embOS distinguishes two different levels of interrupts: High and low priority in-

terrupts. The embOS port-specific documentations explain which interrupts are considered

257 CHAPTER 12 Interrupt latency

high and which are considered low priority for that specific port. In general, the differences

between those two are as follows:

Low priority interrupts

• May call embOS API functions

• Latencies caused by embOS

• Also called “embOS interrupts”

High priority interrupts

• May not call embOS API functions

• No latencies caused by embOS (Zero latency)

• Also called “Zero latency interrupts”

Example of different interrupt priority levels

Let’s assume we have a CPU which supports eight interrupt priority levels. With embOS,

the interrupt levels are divided per default equal in low priority and high priority interrupt

levels. The four highest priority levels are considered “High priority interrupts” and the four

lowest priority interrupts are considered as “Low priority interrupts”. For ARM CPUs, which

support regular interrupts (IRQ) and fast interrupt (FIQ), FIQ is considered as “High priority

interrupt” when using embOS.

For most implementations the high-priority threshold is adjustable. For details, refer to the

processor specific embOS manual.

12.2.5.1 Using embOS API from zero latency interrupts

High priority interrupts are prohibited from using embOS functions. This is a consequence

of embOS’s zero-latency design, according to which embOS never disables high priority

interrupts. This means that high priority interrupts can interrupt the operating system at any

time, even in critical sections such as the modification of RTOS-maintained linked lists. This

design decision has been made because zero interrupt latencies for high priority interrupts

usually are more important than the ability to call OS functions.

However, high priority interrupts may use OS functions in an indirect manner: The high

priority interrupt triggers a low priority interrupt by setting the appropiate interrupt request

flag. Subsequently, that low priority interrupt may call the OS functions that the high priority

interrupt was not allowed to use.

The task 1 is interrupted by a high priority interrupt. This high priority interrupt is not

allowed to call an embOS API function directly. Therefore the high priority interrupt triggers

a low priority interrupt, which is allowed to call embOS API functions. The low priority

interrupt calls an embOS API function to resume task 2.

258 CHAPTER 12 Rules for interrupt handlers

12.3 Rules for interrupt handlers

12.3.1 General rules

There are some general rules for interrupt service routines (ISRs). These rules apply to

both single-task programming as well as to multitask programming using embOS.

• ISR preserves all registers.

Interrupt handlers must restore the environment of a task completely. This environment

normally consists of the registers only, so the ISR must make sure that all registers

modified during interrupt execution are saved at the beginning and restored at the end

of the interrupt routine

• Interrupt handlers must finish quickly.

Intensive calculations should be kept out of interrupt handlers. An interrupt handler

should only be used for storing a received value or to trigger an operation in the regular

program (task). It should not wait in any form or perform a polling operation.

12.3.2 Additional rules for preemptive multitasking

A preemptive multitasking system like embOS needs to know if the code that is executing

is part of the current task or an interrupt handler. This is necessary because embOS cannot

perform a task switch during the execution but only at the end of an ISR.

If a task switch was to occur during the execution of an ISR, the ISR would continue as soon

as the interrupted task became the current task again. This is not a problem for interrupt

handlers that do not allow further interruptions (which do not enable interrupts) and that

do not call any embOS functions.

This leads us to the following rule:

• ISRs that re-enable interrupts or use any embOS function need to call OS_INT_Enter()

at the beginning, before executing anything else, and call OS_INT_Leave() immediately

before returning.

If a higher priority task is made ready by the ISR, the task switch will be performed in the

routine OS_INT_Leave(). The end of the ISR is executed later on, when the interrupted

task has been made ready again. Please consider this behaviour if you debug an interrupt

routine, this has proven to be the most efficient way of initiating a task switch from within

an interrupt service routine.

12.3.3 Nesting interrupt routines

By default, interrupts are disabled in an ISR because most CPU disables interrupts with the

execution of the interrupt handler. Re-enabling interrupts in an interrupt handler allows

the execution of further interrupts with equal or higher priority than that of the current

interrupt. These are known as nested interrupts, illustrated in the diagram below:

259 CHAPTER 12 Rules for interrupt handlers

For applications requiring short interrupt latency, you may re-enable interrupts inside an

ISR by using OS_INT_EnterNestable() and OS_INT_LeaveNestable() within the interrupt

handler.

Nested interrupts can lead to problems that are difficult to debug; therefore it is not rec-

ommended to enable interrupts within an interrupt handler. As it is important that embOS

keeps track of the status of the interrupt enable/disable flag, enabling and disabling of

interrupts from within an ISR must be done using the functions that embOS offers for this

purpose.

The routine OS_INT_EnterNestable() enables interrupts within an ISR and prevents fur-

ther task switches; OS_INT_LeaveNestable() disables interrupts immediately before end-

ing the interrupt routine, thus restoring the default condition. Re-enabling interrupts will

make it possible for an embOS scheduler interrupt to interrupt this ISR. In this case, embOS

needs to know that another ISR is still active and that it may not perform a task switch.

260 CHAPTER 12 Rules for interrupt handlers

12.3.4 API functions

Routine Description

main

Task

ISR

Timer

OS_INT_Call() Entry function for use in an embOS interrupt

handler. ●

OS_INT_CallNestable() Entry function for use in an embOS interrupt

handler. ●

OS_INT_Enter() Informs embOS that interrupt code is execut-

ing. ●

OS_INT_EnterNestable() Informs embOS that interrupt code is execut-

ing and reenables interrupts. ●

OS_INT_InInterrupt() Checks if the calling function runs in an inter-

rupt context. ●●●●

OS_INT_Leave() Informs embOS that the end of the inter-

rupt routine has been reached; executes task

switching within ISR.

●

OS_INT_LeaveNestable() Informs embOS that the end of the inter-

rupt routine has been reached; executes task

switching within ISR.

●

261 CHAPTER 12 Rules for interrupt handlers

12.3.4.1 OS_INT_Call()

Description

Entry function for use in an embOS interrupt handler. Nestable interrupts are disabled.

Prototype

void OS_INT_Call(void ( *pRoutine)());

Parameters

Parameter Description

pRoutine Pointer to a routine that should run on interrupt.

Additional information

OS_INT_Call() can be used as an entry function in an embOS interrupt handler, when the

corresponding interrupt should not be interrupted by another embOS interrupt.

OS_INT_Call() sets the interrupt priority of the CPU to the user definable ’fast’ interrupt

priority level, thus locking any other embOS interrupt. Fast interrupts are not disabled.

Note

For some specific CPUs OS_INT_Call() must be used to call an interrupt handler

because OS_INT_Enter()/OS_INT_Leave() may not be available.

OS_INT_Call() must not be used when OS_INT_Enter()/OS_INT_Leave() is available

Please refer to the CPU/compiler specific embOS manual.

Example

#pragma interrupt

void SysTick_Handler(void) {

OS_INT_Call(_IsrTickHandler);

}

262 CHAPTER 12 Rules for interrupt handlers

12.3.4.2 OS_INT_CallNestable()

Description

Entry function for use in an embOS interrupt handler. Nestable interrupts are enabled.

Prototype

void OS_INT_CallNestable(void ( *pRoutine)());

Parameters

Parameter Description

pRoutine Pointer to a routine that should run on interrupt.

Additional information

OS_INT_CallNestable() can be used as an entry function in an embOS interrupt handler,

when interruption by higher prioritized embOS interrupts should be allowed.

OS_INT_CallNestable() does not alter the interrupt priority of the CPU, thus keeping all

interrupts with higher priority enabled.

Note

For some specific CPUs OS_INT_CallNestable() must be used to call an interrupt han-

dler because OS_INT_EnterNestable()/OS_INT_LeaveNestable() may not be avail-

able.

OS_INT_CallNestable() must not be used when OS_INT_EnterNestable()/OS_IN-

T_LeaveNestable() is available

Please refer to the CPU/compiler specific embOS manual.

Example

#pragma interrupt

void SysTick_Handler(void) {

OS_INT_CallNestable(_IsrTickHandler);

}

263 CHAPTER 12 Rules for interrupt handlers

12.3.4.3 OS_INT_Enter()

Description

Informs embOS that interrupt code is executing.

Prototype

void OS_INT_Enter(void);

Additional information

Note

This function is not available in all ports.

If OS_INT_Enter() is used, it should be the first function to be called in the interrupt

handler. It must be paired with OS_INT_Leave() as the last function called. The use of this

function has the following effects:

• disables task switches

• keeps interrupts in internal routines disabled.

Example

Refer to the example of OS_INT_Leave().

264 CHAPTER 12 Rules for interrupt handlers

12.3.4.4 OS_INT_EnterNestable()

Description

Re-enables interrupts and increments the embOS internal critical region counter, thus dis-

abling further task switches.

Prototype

void OS_INT_EnterNestable(void);

Additional information

Note

This function is not available in all ports.

This function should be the first call inside an interrupt handler when nested interrupts are

required. The function OS_INT_EnterNestable() is implemented as a macro and offers the

same functionality as OS_INT_Enter() in combination with OS_INT_DecRI(), but is more

efficient, resulting in smaller and faster code.

Example

Refer to the example of OS_INT_LeaveNestable().

265 CHAPTER 12 Rules for interrupt handlers

12.3.4.5 OS_INT_InInterrupt()

Description

This function can be called to examine if the calling function is running in an interrupt

context. For application code, it may be useful to know if it is called from interrupt or task,

because some functions must not be called from an interrupt-handler.

Prototype

OS_BOOL OS_INT_InInterrupt(void);

Return value

= 0 Code is not executed in an interrupt handler.

≠ 0 Code is executed in an interrupt handler.

Additional information

Note

This function is not available in all ports.

The function delivers the interrupt state by checking the according CPU registers. It is

only implemented for those CPUs where it is possible to read the interrupt state from CPU

registers. In case of doubt please contact the embOS support.

Example

void foo() {

if (OS_INT_InInterrupt() == 1) {

// Do something within the ISR

} else {

printf("No interrupt context.\n")

}

266 CHAPTER 12 Rules for interrupt handlers

12.3.4.6 OS_INT_Leave()

Description

Informs embOS that the end of the interrupt routine has been reached; executes task

switching within ISR.

Prototype

void OS_INT_Leave(void);

Additional information

Note

This function is not available in all ports.

If OS_INT_Leave() is used, it should be the last function to be called in the interrupt handler.

If the interrupt has caused a task switch, that switch is performed immediately (unless the

program which was interrupted was in a critical region).

Example

void ISR_Timer(void) {

OS_INT_Enter();

OS_TASKEVENT_Set(1, &Task); // Any functionality could be here

OS_INT_Leave();

}

267 CHAPTER 12 Rules for interrupt handlers

12.3.4.7 OS_INT_LeaveNestable()

Description

Disables further interrupts, then decrements the embOS internal critical region count, thus

re-enabling task switches if the counter has reached zero.

Prototype

void OS_INT_LeaveNestable(void);

Additional information

Note

This function is not available in all ports.

This function is the counterpart of OS_INT_EnterNestable(), and must be the last function

call inside an interrupt handler when nested interrupts have been enabled by OS_INT_En-

terNestable().

The function OS_INT_LeaveNestable() is implemented as a macro and offers the same

functionality as OS_INT_Leave() in combination with OS_INT_IncDI(), but is more efficient,

resulting in smaller and faster code.

Example

_interrupt void ISR_Timer(void) {

OS_INT_EnterNestable();

OS_TASKEVENT_Set(1,&Task); // Any functionality could be here

OS_INT_LeaveNestable();

}

268 CHAPTER 12 Interrupt control

12.4 Interrupt control

12.4.1 Enabling / disabling interrupts

During the execution of a task, maskable interrupts are normally enabled. In certain sec-

tions of the program, however, it can be necessary to disable interrupts for short periods

of time to make a section of the program an atomic operation that cannot be interrupted.

An example would be the access to a global volatile variable of type long on an 8/16 bit

CPU. To make sure that the value does not change between the two or more accesses that

are needed, interrupts must be temporarily disabled:

Bad example:

volatile long lvar;

void IntHandler(void) {

lvar++;

}

void routine (void) {

lvar++;

}

Good example:

volatile long lvar;

void IntHandler(voi

lvar++;

}

void routine (void) {

OS_INT_Disable();

lvar++;

OS_INT_Enable();

}

The problem with disabling and re-enabling interrupts is that functions that disable/ enable

the interrupt cannot be nested.

Your C compiler offers two intrinsic functions for enabling and disabling interrupts. These

functions can still be used, but it is recommended to use the functions that embOS offers

(to be precise, they only look like functions, but are macros in reality). If you do not use

these recommended embOS functions, you may run into a problem if routines which require

a portion of the code to run with disabled interrupts are nested or call an OS routine.

We recommend disabling interrupts only for short periods of time, if possible. Also, you

should not call functions when interrupts are disabled, because this could lead to long

interrupt latency times (the longer interrupts are disabled, the higher the interrupt latency).

You may also safely use the compiler-provided intrinsics to disable interrupts but you must

ensure to not call embOS functions with disabled interrupts.

12.4.2 Global interrupt enable / disable

The embOS interrupt enable and disable functions enable and disable embOS interrupts

only. If a system is set up to support high and low priority interrupts and embOS is con-

figured to support “zero latency” interrupts, the embOS functions to enable and disable in-

terrupts affect the low priority interrupts only. High priority interrupts, called “zero latency

interrupts” are never enabled or disabled by embOS functions.

In an application it may be required to disable and enable all interrupts. Since version 3.90,

embOS has API functions which allow enabling and disabling all interrupts. These functions

269 CHAPTER 12 Interrupt control

have the suffix All and allow a “global” handling of the interrupt enable state of the CPU.

These functions affect the state of the CPU unconditionally and should be used with care.

12.4.3 Non-maskable interrupts (NMIs)

embOS performs atomic operations by disabling interrupts. However, a non-maskable in-

terrupt (NMI) cannot be disabled, meaning it can interrupt these atomic operations. There-

fore, NMIs should be used with great care and are prohibited from calling any embOS rou-

tines.

12.4.4 API functions

Routine Description

main

Task

ISR

Timer

OS_INT_DecRI() Decrements the counter and enables

interrupts if the counter reaches 0. ●●●●

OS_INT_Disable() Disables interrupts. Does not change

the interrupt disable counter. ●●●●

OS_INT_Enable() Unconditionally enables interrupts. ● ● ● ●

OS_INT_EnableConditional() Restores the state of the interrupt

flag, based on the interrupt disable

counter.

●●●●

OS_INT_IncDI() Increments the interrupt disable

counter (OS_Global.Counters.DI)

and disables interrupts.

●●●●

OS_INT_Preserve() Preserves the embOS interrupt

state. ●●●●

OS_INT_Restore() Restores the embOS interrupt state. ● ● ● ●

OS_INT_DisableAll() Disable all interrupts (high and low

priority) unconditionally. ●●●●

OS_INT_PreserveAndDisableAll() Preserves the current interrupt en-

able state and then disables all in-

terrupts.

●●●●

OS_INT_PreserveAll() Preserves the current interrupt en-

able state. ●●●●

OS_INT_RestoreAll() Restores the interrupt enable state

which was preserved before. ●●●●

OS_INT_EnableAll() Enable all interrupts (high and low

priority) unconditionally. ●●●●

270 CHAPTER 12 Interrupt control

12.4.4.1 OS_INT_IncDI() / OS_INT_DecRI()

Description

The following functions are actually macros defined in RTOS.h, so they execute very quickly

and are very efficient. It is important that they are used as a pair: first OS_INT_IncDI(),

then OS_INT_DecRI().

12.4.4.1.1 OS_INT_IncDI()

Short for Increment and Disable Interrupts. Increments the interrupt disable counter

(OS_Global.Counters.DI) and disables interrupts.

12.4.4.1.2 OS_INT_DecRI()

Short for Decrement and Restore Interrupts. Decrements the counter and enables inter-

rupts if the disable counter reaches zero.

Additional information

OS_INT_IncDI() increments the interrupt disable counter, interrupts will not be switched

on within the running task before the matching OS_INT_DecRI() is executed. The counter

is task specific, a task switch may change the value, so if interrupts are disabled they could

be enabled in the next task and vice versa.

If you need to disable interrupts for a instant only where no routine is called, as in the

example above, you could also use the pair OS_INT_Disable() and OS_INT_EnableCondi-

tional(). These are slightly more efficient because the interrupt disable counter OS_DICnt

is not modified twice, but only checked once. They have the disadvantage that they do not

work with functions because the status of OS_DICnt is not actually changed, and they should

therefore be used with great care. In case of doubt, use OS_INT_IncDI() and OS_INT_De-

cRI(). You can safely call embOS API between OS_INT_IncDI() and OS_INT_DecRI(). The

embOS API will not enable interrupts.

Example

volatile long lvar;

void routine (void) {

OS_INT_IncDI();

lvar ++;

OS_INT_DecRI();

}

271 CHAPTER 12 Interrupt control

12.4.4.2 OS_INT_Disable()

OS_INT_Disable() disables embOS interrupts but does not change the interrupt disable

counter OS_Global.Counters.Cnt.DI.

12.4.4.3 OS_INT_Enable()

OS_INT_Enable() enables embOS interrupts but does not check the interrupt disable

counter OS_Global.Counters.Cnt.DI. Refrain from using this function directly unless you

are sure that the interrupt disable count has the value zero, because it does not take the

interrupt disable counter into account. OS_INT_Disable() / OS_INT_Enable() can be used

when no embOS API functions are called between which could enable interrupts before the

actual call to OS_INT_Enable() and the interrupt disable count is zero.

12.4.4.4 OS_INT_EnableConditional()

Restores the interrupt status, based on the interrupt disable counter. interrupts are only

enabled if the interrupt disable counter OS_Global.Counters.Cnt.DI is zero.

Example

volatile long lvar;

void routine (void) {

OS_INT_Disable();

lvar++;

OS_INT_EnableConditional();

}

You cannot safely call embOS API between OS_INT_Disable() and OS_INT_Enable()/

OS_INT_EnableConditional(). The embOS API might already enable interrupts because

OS_INT_Disable() does not change the interrupt disable counter. In that case please use

OS_INT_IncDI() and OS_INT_DecRI() instead.

272 CHAPTER 12 Interrupt control

12.4.4.5 OS_INT_Preserve()

Description

This function can be called to preserve the current embOS interrupt enable state of the CPU.

Prototype

void OS_INT_Preserve(OS_U32* pState);

Parameters

Parameter Description

pState Pointer to an OS_U32 variable that receives the interrupt

state.

Additional information

If the interrupt enable state is not known and interrupts should be disabled by a call of

OS_INT_Disable(), the current embOS interrupt enable state can be preserved and re-

stored later by a call of OS_INT_Restore().

Example

void Sample(void) {

OS_U32 IntState;

OS_INT_Preserve(&IntState); // Remember the interrupt enable state.

OS_INT_Disable(); // Disable embOS interrupts

// Execute any code that should be executed with embOS interrupts disabled

...

OS_INT_Restore(&IntState); // Restore the interrupt enable state

}

273 CHAPTER 12 Interrupt control

12.4.4.6 OS_INT_Restore()

Description

This function must be called to restore the embOS interrupt enable state of the CPU which

was preserved before.

Prototype

void OS_INT_Restore (OS_U32* pState);

Parameters

Parameter Description

pState Pointer to an OS_U32 variable that holds the interrupt enable

state.

Additional information

Restores the embOS interrupt enable state which was saved before by a call of OS_IN-

T_Preserve(). If embOS interrupts were enabled before they were disabled, the function

reenables them.

Example

void Sample(void) {

OS_U32 IntState;

OS_INT_Preserve(&IntState); // Remember the interrupt enable state.

OS_INT_Disable(); // Disable embOS interrupts

// Execute any code that should be executed with embOS interrupts disabled

...

OS_INT_Restore(&IntState); // Restore the interrupt enable state

}

274 CHAPTER 12 Interrupt control

12.4.4.7 OS_INT_DisableAll()

Description

This function disables embOS and zero latency interrupts unconditionally.

Prototype

void OS_INT_DisableAll(void);

Additional information

OS_INT_DisableAll() disables all interrupts (including zero latency interrupts) in a fast

and efficient way. Note that the system does not track the interrupt state when calling the

function. Therefore the function should not be called when the state is unknown. Interrupts

can be re-enabled by calling OS_INT_EnableAll(). After calling OS_INT_DisableAll(),

no embOS function except the interrupt enable function OS_INT_EnableAll() should be

called, because the interrupt state is not saved by the function. An embOS API function

may re-enable interrupts. The exact interrupt enable behaviour depends on the CPU.

275 CHAPTER 12 Interrupt control

12.4.4.8 OS_INT_PreserveAndDisableAll()

Description

This function preserves the current interrupt enable state of the CPU and then disables

embOS and zero latency interrupts.

Prototype

void OS_INT_PreserveAndDisableAll (OS_U32* pState);

Parameters

Parameter Description

pState Pointer to an OS_U32 variable that receives the interrupt

state.

Additional information

The function store the current interrupt enable state into the variable pointed to by pState

and then disables embOS and zero latency interrupts. The interrupt state can be restored

later by a corresponding call of OS_INT_RestoreAll().

The pair of function calls OS_INT_PreserveAndDisableAll() and OS_INT_RestoreAll()

can be nested, as long as the interrupt enable state is stored into an individual variable on

each call of OS_INT_PreserveAndDisableAll(). This function pair should be used when

the interrupt enable state is not known when interrupts shall be enabled.

Example

void Sample(void) {

OS_U32 IntState;

// Remember the interrupt enable state and disables interrupts.

OS_INT_PreserveAndDisableAll(&IntState);

// Execute any code that should be executed with interrupts disabled

// No embOS function should be called

...

OS_INT_RestoreAll(&IntState); // Restore the interrupt enable state

}

276 CHAPTER 12 Interrupt control

12.4.4.9 OS_INT_PreserveAll()

Description

This function can be called to preserve the current interrupt enable state of the CPU.

Prototype

void OS_INT_PreserveAll (OS_U32* pState);

Parameters

Parameter Description

pState Pointer to an OS_U32 variable that receives the interrupt

state.

Additional information

If the interrupt enable state is not known and interrupts should be disabled by a call of

OS_INT_DisableAll(), the current interrupt enable state can be preserved and restored

later by a call of OS_INT_RestoreAll(). Note that the interrupt state is not stored by

embOS. After disabling the interrupts using a call of OS_INT_DisableAll(), no embOS API

function should be called because embOS functions might re-enable interrupts.

Example

void Sample(void) {

OS_U32 IntState;

// Remember the interrupt enable state.

OS_INT_PreserveAll(&IntState);

OS_INT_DisableAll(); // Disable interrupts

// Execute any code that should be executed with interrupts disabled

// No embOS function should be called

...

OS_INT_RestoreAll(&IntState); // Restore the interrupt enable state

}

277 CHAPTER 12 Interrupt control

12.4.4.10 OS_INT_RestoreAll()

Description

This function must be called to restore the interrupt enable state of the CPU which was

preserved before.

Prototype

void OS_INT_RestoreAll (OS_U32* pState);

Parameters

Parameter Description

pState Pointer to an OS_U32 variable that holds the interrupt enable

state.

Additional information

Restores the interrupt enable state which was saved before by a call of OS_INT_Pre-

serveAll() or OS_INT_PreserveAndDisableAll(). If interrupts were enabled before they

were disabled globally, the function reenables them.

Example

void Sample(void) {

OS_U32 IntState;

// Remember the interrupt enable state.

OS_INT_PreserveAll(&IntState);

OS_INT_DisableAll(); // Disable interrupts

// Execute any code that should be executed with interrupts disabled

// No embOS function should be called

...

OS_INT_RestoreAll(&IntState); // Restore the interrupt enable state

}

278 CHAPTER 12 Interrupt control

12.4.4.11 OS_INT_EnableAll()

Description

This function enables high and low priority interrupts unconditionally.

Prototype

void OS_INT_EnableAll(void);

Additional information

This function re-enables interrupts which were disabled before by a call of OS_INT_Dis-

ableAll(). The function re-enables embOS and zero latency interrupts unconditionally.

OS_INT_DisableAll() and OS_INT_EnableAll() should be used as a pair. The call cannot

be nested, because the state is not saved. This kind of global interrupt disable/enable should

only be used when the interrupt enable state is well known and interrupts are enabled.

Between OS_INT_DisableAll() and OS_INT_EnableAll(), no function should be called

when it is not known if the function alters the interrupt enable state.

If the interrupt state is not known, the functions OS_INT_PreserveAll() or OS_INT_Pre-

serveAndDisableAll() and OS_INT_RestoreAll() shall be used as decribed later on.

Example

void Sample(void) {

OS_INT_DisableAll(); // Disable interrupts

// Execute any code that should be executed with interrupts disabled

// No embOS function should be called

...

OS_INT_EnableAll(); // Re-enable interrupts unconditionally

}

Chapter 13

Critical Regions

280 CHAPTER 13 Introduction

13.1 Introduction

Critical regions are program sections during which preemptive task switches are disabled,

meaning that no task switch and no execution of software timers are allowed except in

situations where the running task must wait. Cooperative task switches are not affected

and will be executed in critical regions.

A typical example for a critical region would be the execution of a program section that

handles a time-critical hardware access (for example writing multiple bytes into an EEPROM

where the bytes must be written in a certain amount of time), or a section that writes data

into global variables used by a different task and therefore needs to make sure the data

is consistent.

A critical region can be defined anywhere during the execution of a task. Critical regions

can be nested; the scheduler will be switched on again after the outermost region is left.

Interrupts are still legal in a critical region. Software timers and interrupts are executed

as critical regions anyhow, so it does not hurt but does not do any good either to declare

them as such. If a task switch becomes due during the execution of a critical region, it will

be performed immediately after the region is left.

Example

void HPTask(void) {

OS_TASK_EnterRegion();

DoSomething(); // This code will not be interrupted by other tasks

OS_TASK_LeaveRegion();

}

Note

Cooperative task switches will still be executed although preemptive task switches are

disabled in a critical section.

void HPTask(void) {

OS_TASK_EnterRegion();

OS_TASK_Delay(100); // OS_TASK_Delay() will cause a cooperative task switch

OS_TASK_LeaveRegion();

}

281 CHAPTER 13 API functions

13.2 API functions

Routine Description

main

Task

ISR

Timer

OS_TASK_EnterRegion() Indicates to embOS the beginning of a critical

region. ●●●●

OS_TASK_LeaveRegion() Indicates to embOS the end of a critical region. ● ● ● ●

282 CHAPTER 13 API functions

13.2.1 OS_TASK_EnterRegion()

Description

Indicates to embOS the beginning of a critical region.

Prototype

void OS_TASK_EnterRegion(void);

Additional information

A critical region counter (OS_Global.Counters.Cnt.Region), which is zero by default, is

incremented so that critical regions can be nested. The counter will be decremented by

a call to the routine OS_TASK_LeaveRegion(). When this counter reaches zero again, the

critical region ends.

Interrupts are not disabled using OS_TASK_EnterRegion(). However, preemptive task

switches are disabled in a critical region. If any interrupt triggers a task switch, the task

switch is delayed and kept pending until the final call of OS_TASK_LeaveRegion(). When

the counter reaches zero, any pending task switch is executed.

Cooperative task switches are not affected and will be executed in critical regions. When a

task is running in a critical region and calls any blocking embOS function, the task will be

suspended. When the task is resumed, the task-specific critical region counter is restored,

the task continues to run in a critical region until OS_TASK_LeaveRegion() is called.

283 CHAPTER 13 API functions

13.2.2 OS_TASK_LeaveRegion()

Description

Indicates to embOS the end of a critical region. Decrements the critical region counter and

checks if a task switch is pending if the counter reaches 0.

Prototype

void OS_TASK_LeaveRegion(void);

Additional information

A critical region counter (OS_Global.Counters.Cnt.Region), which is zero by default, is

decremented. If this counter reaches zero, the critical region ends. A task switch which

became pending during a critical region will be executed in OS_TASK_EnterRegion() when

the counter reaches zero.

Chapter 14

Time Measurement

285 CHAPTER 14 Introduction

14.1 Introduction

embOS supports two basic types of run-time measurement which may be used for calcu-

lating the execution time of any section of user code. Low-resolution measurements are

based on system ticks, while high-resolution measurements are based on a time unit called

cycle. The length of a cycle depends on the timer clock frequency.

Example

OS_TIME BenchmarkLoRes(void) {

OS_TIME t;

t = OS_TIME_GetTicks();

DoSomething(); // Code to be benchmarked

t = OS_TIME_GetTicks() - t;

return t;

}

OS_U32 BenchmarkHiRes(void) {

OS_TIMING t;

OS_TIME_StartMeasurement(&t);

DoSomething(); // Code to be benchmarked

OS_TIME_StopMeasurement(&t);

return OS_TIME_GetResultus(&t);

}

286 CHAPTER 14 Low-resolution measurement

14.2 Low-resolution measurement

The global system time variable OS_Global.Time is measured in system ticks, which

typically equal milliseconds. The low-resolution functions OS_TIME_GetTicks() and

OS_TIME_GetTicks32() are used for returning the current contents of this variable. The

basic concept behind low-resolution measurement is quite simple: The system time is re-

turned once before the section of code to be timed and once after, and the first value is

subtracted from the second to obtain the time it took for the code to execute.

The term low-resolution is used because the time values returned are measured in com-

pleted system ticks. Consider the following: The global variable OS_Global.Time is incre-

mented with every system tick interrupt, with a default tick of one msec that means once

each msec. This means that the actual system time can potentially be later than the low-

resolution function returns (for example, if an interrupt actually occurs at system 1.4 ticks,

the system will assume only one tick having elapsed). The problem even gets worse when

concerning runtime measurement, because the system time must be measured twice. Since

each measurement can, potentially, be up to one tick less than the actual time, the differ-

ence between two measurements could theoretically be inaccurate by up to one tick.

The following diagram illustrates how low-resolution measurement works. We can see that

the section of code begins at 0.5 msec and ends at 5.2 msec, which means that its exact

execution time is 5.2 msec - 0.5 mesec = 4.7 msec. However, assuming one system tick per

msec, the first call to OS_TIME_GetTicks() will return 0, while the second call will return

5. The measured execution time would therefore be returned as 5 system ticks - 0 system

ticks = 5 system ticks.

For many applications, low-resolution measurement is sufficient for most of all cases. In

those cases, its ease of use as well as its faster computation time are clear benefits when

compared to high-resolution measurement. Still, high-resolution measurement may be nec-

essary when highly accurate measurements are mandatory.

14.2.1 API functions

Routine Description

main

Task

ISR

Timer

OS_TIME_GetTicks() Returns the current system time in sytem ticks

as a native integer value. ●●●●

OS_TIME_GetTicks32() Returns the current system time in system ticks

as a 32 bit integer value. ●●●●

287 CHAPTER 14 Low-resolution measurement

14.2.1.1 OS_TIME_GetTicks()

Description

Returns the current system time in ticks as a native integer value.

Prototype

int OS_TIME_GetTicks(void);

Return value

The system variable OS_Global.Time as a 16 bit integer value on 8/16 bit CPUs, and as

a 32 bit integer value on 32 bit CPUs.

Additional information

The OS_Global.Time variable is a 32 bit integer value. Therefore, if the return value is 32

bit, it holds the entire contents of the OS_Global.Time variable. If the return value is 16

bit, it holds the lower 16 bits of the OS_Global.Time variable.

Example

void PrintTask(void) {

int Time;

Time = OS_TIME_GetTicks();

printf("System Time: %d\n", Time);

}

288 CHAPTER 14 Low-resolution measurement

14.2.1.2 OS_TIME_GetTicks32()

Description

Returns the current system time in system ticks as a 32 bit integer value.

Prototype

OS_I32 OS_TIME_GetTicks32(void);

Return value

The system variable OS_Global.Time as a 32 bit integer value.

Additional information

This function always returns the system time as a 32 bit value. Because the OS_Glob-

al.Time variable is also a 32 bit value, the return value is simply the entire contents of

the OS_Global.Time variable.

Example

void PrintTask(void) {

OS_I32 Time;

Time = OS_TIME_GetTicks32();

printf("System Time: %d\n", Time);

}

289 CHAPTER 14 High-resolution measurement

14.3 High-resolution measurement

High-resolution measurement uses the same routines as those used in profiling builds of

embOS, allowing fine-tuning of time measurement. While system resolution depends on

the CPU used, it is typically about one microsecond, making high-resolution measurement

1000 times more accurate than low-resolution calculations.

Instead of measuring the number of completed system ticks at a given time, an internal

count is kept of the number of cycles that have been completed at a given time. Please

refer to the illustration below, which measures the execution time of the same code that

was used during the low-resolution calculation. For this example, we assume that the CPU

has a timer running at 10 MHz and counts upwards. The number of cycles per tick therefore

equals (10 MHz / 1 kHz) = 10,000. This means that with each tick-interrupt, the timer

restarts at zero and counts up to 10,000.

The call to OS_TIME_StartMeasurement() calculates the starting value at 5,000 cycles,

while the call to OS_TIME_StopMeasurement() calculates the ending value at 52,000 cycles

(both values are kept track of internally). The measured execution time of the code in this

example would therefore be (52,000 cycles - 5,000 cycles) = 47,000 cycles, which equals

4.7 msec.

Although the function OS_TIME_GetResult() may be used for returning the execution time

in cycles as above, it is typically more common to use the function OS_TIME_GetResultus(),

which returns the value in microseconds. In the above example, the return value would

be 4,700 usec.

290 CHAPTER 14 High-resolution measurement

14.3.1 API functions

Routine Description

main

Task

ISR

Timer

OS_TIME_StartMeasure-

ment() Marks the beginning of a code section to be

timed. ●●●●

OS_TIME_StopMeasure-

ment() Marks the end of a code section to be timed. ● ● ● ●

OS_TIME_GetResult() Returns the execution time of the code between

OS_TIME_StartMeasurement() and OS_TIME_S-

topMeasurement() in timer cycles.

●●●●

OS_TIME_GetResultus() Returns the execution time of the code between

OS_TIME_StartMeasurement() and OS_TIME_S-

topMeasurement() in microseconds.

●●●●

291 CHAPTER 14 High-resolution measurement

14.3.1.1 OS_TIME_StartMeasurement()

Description

Marks the beginning of a code section to be timed.

Prototype

void OS_TIME_StartMeasurement(OS_TIMING* pCycle);

Parameters

Parameter Description

pCycle Pointer to a data structure of type OS_TIMING.

Additional information

This function must be used with OS_TIME_StopMeasurement().

Example

Please refer to the Example on page 295.

292 CHAPTER 14 High-resolution measurement

14.3.1.2 OS_TIME_StopMeasurement()

Description

Marks the end of a code section to be timed.

Prototype

void OS_TIME_StopMeasurement(OS_TIMING* pCycle);

Parameters

Parameter Description

pCycle Pointer to a data structure of type OS_TIMING.

Additional information

This function must be used with OS_TIME_StartMeasurement().

Example

Please refer to the Example on page 295.

293 CHAPTER 14 High-resolution measurement

14.3.1.3 OS_TIME_GetResult()

Description

Returns the execution time of the code between OS_TIME_StartMeasurement() and

OS_TIME_StopMeasurement() in timer cycles.

Prototype

OS_U32 OS_TIME_GetResult(OS_TIMING* pCycle);

Parameters

Parameter Description

pCycle Pointer to a data structure of type OS_TIMING.

Return value

The execution time in timer cycles as a 32 bit integer value.

Additional information

Cycle length depends on the timer clock frequency.

Example

Please refer to the Example of OS_TIME_GetResultus(), with the only difference that this

function returns cycles instead of microseconds.

294 CHAPTER 14 High-resolution measurement

14.3.1.4 OS_TIME_GetResultus()

Description

Returns the execution time of the code between OS_TIME_StartMeasurement() and

OS_TIME_StopMeasurement() in microseconds.

Prototype

OS_U32 OS_TIME_GetResultus(OS_CONST_PTR OS_TIMING *pCycle);

Parameters

Parameter Description

pCycle Pointer to a data structure of type OS_TIMING.

Return value

The execution time in microseconds (usec) as a 32-bit integer value.

Example

Please refer to the Example on page 295.

295 CHAPTER 14 Example

14.4 Example

The following sample demonstrates the use of low-resolution and high-resolution measure-

ment to return the execution time of a section of code:

#include "RTOS.h"

#include <stdio.h>

static OS_STACKPTR int Stack[1000]; // Task stacks

static OS_TASK TCB; // Task-control-blocks

static volatile int Dummy;

void UserCode(void) {

for (Dummy=0; Dummy < 11000; Dummy++); // Burn some time

}

// Measure the execution time with low resolution

int BenchmarkLoRes(void) {

OS_TIME t;

t = OS_TIME_GetTicks();

UserCode(); /* Execute the user code to be benchmarked */

t = OS_TIME_GetTicks() - t;

return (int)t;

}

// Measure the execution time with high resolution

OS_U32 BenchmarkHiRes(void) {

OS_TIMING t;

OS_TIME_StartMeasurement(&t);

UserCode(); // Execute the user code to be benchmarked

OS_TIME_StopMeasurement(&t);

return OS_TIME_GetResultus(&t);

}

void Task(void) {

int tLo;

OS_U32 tHi;

char ac[80];

while (1) {

tLo = BenchmarkLoRes();

tHi = BenchmarkHiRes();

sprintf(ac, "LoRes: %d system ticks\n", tLo);

OS_COM_SendString(ac);

sprintf(ac, "HiRes: %d usec\n", tHi);

OS_COM_SendString(ac);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize hardware for embOS

OS_TASK_CREATE(&TCB, "HP Task", 100, Task, Stack);

OS_Start(); // Start multitasking

return 0;

}

The output of the sample is as follows:

LoRes: 7 system ticks

HiRes: 6641 usec

296 CHAPTER 14 Microsecond precise system time

14.5 Microsecond precise system time

The following functions return the current system time in microsecond resolution. The func-

tion OS_TIME_ConfigSysTimer() sets up the necessary parameters.

14.5.1 API functions

Routine Description

main

Task

ISR

Timer

OS_TIME_ConfigSysTimer() Configures the system time parameters

for the functions OS_TIME_Getus() and

OS_TIME_Getus64().

●

OS_TIME_Getus() Returns the current system time in mi-

croseconds as a 32 bit value. ●●●●

OS_TIME_Getus64() Returns the current system time in mi-

croseconds as a 64 bit value. ●●●●

297 CHAPTER 14 Microsecond precise system time

14.5.1.1 OS_TIME_ConfigSysTimer()

Description

Configures the system time parameters for the functions OS_TIME_Getus() and

OS_TIME_Getus64().

This function usually is called once from OS_InitHW() (implemented in RTOSInit.c).

Prototype

void OS_TIME_ConfigSysTimer(OS_CONST_PTR OS_SYSTIMER_CONFIG *pConfig);

Parameters

Parameter Description

pConfig Pointer to a data structure of type OS_SYSTIMER_CONFIG.

14.5.1.1.1 The OS_SYSTIMER_CONFIG struct

OS_TIME_ConfigSysTimer() uses the struct OS_SYSTIMER_CONFIG:

Member Description

TimerFreq Timer frequency in Hz

TickFreq Tick frequency in Hz

IsUpCounter 0: for hardware timer which counts down

1: for hardware timer which counts up

pfGetTimerCycles Pointer to a function which returns the current

hardware timer count value

pfGetTimerIntPending Pointer to a function which indicates whether the

hardware timer interrupt pending flag is set

pfGetTimerCycles()

Description

This callback function must be implemented by the user. It returns the current hardware

timer count value.

Prototype

unsigned int (*pfGetTimerCycles)(void);

Return value

The current hardware timer count value.

pfGetTimerIntPending()

Description

This callback function must be implemented by the user. It returns a value unequal to zero

if the hardware timer interrupt pending flag is set.

Prototype

unsigned int (*pfGetTimerIntPending)(void);

Return value

= 0 Hardware timer interrupt pending flag is not set.

298 CHAPTER 14 Microsecond precise system time

≠ 0 The pending flag is set.

Example

#define OS_FSYS 72000000u // 72 MHz CPU main clock

#define OS_PCLK_TIMER (OS_FSYS) // HW timer runs at CPU speed

#define OS_TICK_FREQ 1000u // 1 KHz => 1 msc per system tick

static unsigned int _OS_GetHWTimer_Cycles(void) {

return HW_TIMER_VALUE_REG;

}

static unsigned int _OS_GetHWTimer_IntPending(void) {

return HW_TIMER_INT_REG & (1uL << PENDING_BIT);

}

const OS_SYSTIMER_CONFIG Tick_Config = { OS_PCLK_TIMER,

OS_TICK_FREQ,

_OS_GetHWTimer_Cycles

_OS_GetHWTimer_IntPending };

void OS_InitHW(void) {

OS_TIME_ConfigSysTimer(&Tick_Config);

...

}

299 CHAPTER 14 Microsecond precise system time

14.5.1.2 OS_TIME_Getus()

Description

Returns the current system time in microseconds as a 32 bit value.

Prototype

OS_U32 OS_TIME_Getus(void);

Return value

The current system time in microseconds (usec) as a 32-bit integer value.

Additional information

OS_TIME_Getus() returns correct values only if OS_TIME_ConfigSysTimer() was called

during initialization. All embOS board support packages already call OS_TIME_ConfigSys-

Timer(). With this 32 bit value OS_TIME_Getus() can return up to 4249 seconds or ~71

minutes.

Example

void PrintTime(void) {

OS_U32 Time;

Time = OS_TIME_Getus();

printf("System Time: %u usec\n", Time);

}

300 CHAPTER 14 Microsecond precise system time

14.5.1.3 OS_TIME_Getus64()

Description

Returns the current system time in microseconds as a 64 bit value.

Prototype

OS_U64 OS_TIME_Getus64(void);

Return value

The current system time in microseconds (usec) as a 64-bit integer value.

Additional information

This function is unavailable for compilers that do not support a 64 bit data type (long long).

This is the case only for very rare older 8/16 bit compiler. All 32 bit compiler support a

64 bit data type.

OS_TIME_Getus64() returns correct values only if OS_TIME_ConfigSysTimer() was called

during initialization. All embOS board support packages already call OS_TIME_ConfigSys-

Timer(). With this 64 bit value OS_TIME_Getus64() can return up to 18446744073709

seconds or ~584942 years.

Example

void MeasureTime(void) {

OS_U64 t0, t1;

OS_U32 delta;

t0 = OS_TIME_Getus64();

DoSomething();

t1 = OS_TIME_Getus64();

delta = (OS_U32)(t1 - t0);

printf("Delta: %u usec\n", delta);

}

Chapter 15

Low Power Support

302 CHAPTER 15 Introduction

15.1 Introduction

embOS provides several means to control the power consumption of your target hardware.

These include

• The possibility to enter power save modes with the embOS function OS_Idle().

• The embOS tickless support, allowing the microcontroller to remain in a power save

mode for extended periods of time.

• The embOS peripheral power control module, which allows control of the power

consumption of specific peripherals.

The following chapter explains each of these in more detail.

303 CHAPTER 15 Starting power save modes in OS_Idle()

15.2 Starting power save modes in OS_Idle()

In case your controller supports some kind of power save mode, it is possible to use it with

embOS. To enter that mode, you would usually implement the respective functionality in

the function OS_Idle(), which is located inside the embOS source file RTOSInit.c.

OS_Idle() is executed whenever no task is ready for execution. With many embOS start

projects it is preconfigured to activate a power save mode of the target CPU. Please note

that the available power save modes are hardware-dependant. For example with Cortex-M

CPUs, the wfi instruction is executed per default in OS_Idle() to put the CPU into a power

save mode:

void OS_Idle(void) { // Idle loop: No task is ready to execute

while (1) {

__asm(" wfi"); // Enter sleep mode

}

For further information on OS_Idle(), please also refer to OS_Idle() on page 304.

304 CHAPTER 15 Tickless support

15.3 Tickless support

The embOS tickless support stops the periodic system tick interrupt during idle periods.

Idle periods are periods of time when there are no tasks and no software timer ready

for execution and no interrupt request is pending. Stopping the system tick allows the

microcontroller to remain in a power save mode until an interrupt occurs.

The embOS tickless support comes with the functions OS_TICKLESS_GetNumIdleTicks(),

OS_TICKLESS_AdjustTime(), OS_TICKLESS_Start() and OS_TICKLESS_Stop(). These can

be used to add tickless support to any embOS start project.

15.3.1 OS_Idle()

In order to use the tickless support the OS_Idle() function needs to be modified. The

default OS_Idle() function is just an endless loop which starts a power save mode:

void OS_Idle(void) {

while (1) {

_EnterLowPowerMode();

}

The tickless OS_Idle() function depends on the hardware:

void OS_Idle(void) {

OS_TIME IdleTicks;

OS_INT_Disable();

IdleTicks = OS_TICKLESS_GetNumIdleTicks();

if (IdleTicks > 1) {

if ((OS_U32)IdleTicks > TIMER1_MAX_TICKS) {

IdleTicks = TIMER1_MAX_TICKS;

}

OS_TICKLESS_Start(IdleTicks, &_EndTicklessMode);

_SetHWTimer(IdleTicks);

}

OS_INT_Enable();

while (1) {

_EnterLowPowerMode();

}

The following description explains the tickless OS_Idle() function step by step:

void OS_Idle(void) {

OS_TIME IdleTicks;

OS_INT_Disable();

Interrupts are disabled to avoid a timer interrupt.

IdleTicks = OS_TICKLESS_GetNumIdleTicks();

if (IdleTicks > 1) {

The OS_Idle() function evaluates the number of idle system ticks by calling OS_TICK-

LESS_GetNumIdleTicks(). The tickless mode is only used when there is more than one idle

system tick: If there is one (or none) idle system tick only, the scheduler will be executed

with the next system tick, hence it makes no sense to enter the tickless mode in that case.

if ((OS_U32)IdleTicks > TIMER_MAX_TICKS) {

IdleTicks = TIMER_MAX_TICKS;

}

If it is not possible to generate the timer interrupt at the specified time, e.g. due to hardware

timer limitations, the idle system ticks can be reduced to any lower value. For example, if

305 CHAPTER 15 Tickless support

OS_TICKLESS_GetNumIdleTicks() returns 200 idle system ticks, but the hardware timer’s

duration is limited to 100 ticks maximum, the variable IdleTicks will initially be set to 100

system ticks. The system will then wake up after 100 system ticks, OS_Idle() will be

executed once more and OS_TICKLESS_GetNumIdleTicks() now returns the remaining 100

idle systems ticks, for which tickless mode is entered once again. This means that the

system wakes up two times for the entire 200 idle system ticks.

if (IdleTicks > 1) {

...

OS_TICKLESS_Start(IdleTicks, &_EndTicklessMode);

_SetHWTimer(IdleTicks);

}

OS_TICKLESS_Start() sets the idle system ticks and the callback function. IdleTicks is later

used in the callback function, which is described in more detail below. _SetHWTimer() is

a hardware-dependent function that reprograms the hardware timer to generate a system

tick interrupt at the time defined by IdleTicks.

OS_INT_Enable();

while (1) {

_EnterLowPowerMode();

}

Interrupts are reenabled and the CPU continually enters power save mode. _EnterLowPow-

erMode() is a hardware-dependent function that activates the power save mode.

15.3.2 Callback Function

The callback function calculates how long the processor slept in power save mode and

corrects the system time accordingly.

static void _EndTicklessMode(void) {

OS_U32 NumTicks;

if (OS_Global.TicklessExpired) {

OS_TICKLESS_AdjustTime(OS_Global.TicklessFactor);

} else {

NumTicks = _GetLowPowerTicks();

OS_TICKLESS_AdjustTime(NumTicks);

}

_SetHWTimer(OS_TIMER_RELOAD);

}

The following description explains the callback function step by step:

static void _EndTicklessMode(void) {

OS_U32 NumTicks;

if (OS_Global.TicklessExpired) {

OS_TICKLESS_AdjustTime(OS_Global.TicklessFactor);

If the hardware timer expired and the system tick interrupt was executed the flag OS_Glob-

al.TicklessExpired is set. This can be used to determine if the system slept in power save

mode for the entire idle time. If this flag is set we can use the value in OS_Global.Tick-

lessFactor to adjust the system time.

} else {

NumTicks = _GetLowPowerTicks();

OS_TICKLESS_AdjustTime(NumTicks);

}

306 CHAPTER 15 Tickless support

_GetLowPowerTicks() is a hardware-dependent function which returns the expired idle

ticks if the power save mode was interrupted by any other interrupt than the system tick.

We use that value to adjust the system time.

_SetHWTimer(OS_TIMER_RELOAD);

}

_SetHWTimer() is a hardware-dependent function which reprograms the hardware timer

to its default value for one system tick.

15.3.3 API functions

Routine Description

main

Task

ISR

Timer

Idle

OS_TICKLESS_AdjustTime() Adjusts the embOS internal time

variable by the specified amount of

system ticks.

●●●●

OS_TICKLESS_GetNumIdleTicks()

Retrieves the number of embOS

embOS system ticks until the next

time-scheduled action will be start-

ed.

●

OS_TICKLESS_Start() Start the tickless mode. ●

OS_TICKLESS_Stop() Prematurely stops the tickless

mode. ●

307 CHAPTER 15 Tickless support

15.3.3.1 OS_TICKLESS_AdjustTime()

Description

Adjusts the embOS internal time variable by the specified amount of system ticks.

Prototype

void OS_TICKLESS_AdjustTime(OS_TIME Time);

Parameters

Parameter Description

Time The amount of time which should be added to the embOS in-

ternal time variable.

Additional information

The function may be useful when the embOS system timer was halted for any interval

of time with a well-known duration. When the embOS timer is subsequently re-started,

the internal time variable must be adjusted to that duration in order to guarantee time-

scheduled actions are performed accuratetely.

Example

Please refer to the example described in OS_Idle() on page 304.

308 CHAPTER 15 Tickless support

15.3.3.2 OS_TICKLESS_GetNumIdleTicks()

Description

Retrieves the number of embOS embOS system ticks until the next time-scheduled action

will be started.

Prototype

OS_TIME OS_TICKLESS_GetNumIdleTicks(void);

Return value

> 0 Number of system ticks until next time scheduled action.

= 0 A time scheduled action is pending.

Additional information

The function may be useful when the embOS timer and CPU shall be halted by the appli-

cation and restarted after the idle time to save power. This works when the application has

its own time base and a special interrupt that can wake up the CPU.

When the embOS timer is started again the internal time must be adjusted to guarantee

time-scheduled actions to be executed. This can be done by a call of OS_TICKLESS_Ad-

justTime().

Example

Please refer to the example described in OS_Idle() on page 304.

309 CHAPTER 15 Tickless support

15.3.3.3 OS_TICKLESS_Start()

Description

Start the tickless mode. It sets the sleep time and the user callback function which is called

from the scheduler after wakeup from power save mode.

Prototype

void OS_TICKLESS_Start(OS_TIME Time,

voidRoutine* Callback);

Parameters

Parameter Description

Time Time in ticks which will be spent in power save mode.

Callback Callback function to stop the tickless mode.

Additional information

It must be called before the CPU enters a power save mode.

The callback function must stop the tickless mode. It must calculate how many system ticks

are actually spent in lower power mode and adjust the system time by calling OS_TICK-

LESS_AdjustTime(). It also must reset the system tick timer to it’s default tick period.

Example

Please refer to the example described in OS_Idle() on page 304.

310 CHAPTER 15 Tickless support

15.3.3.4 OS_TICKLESS_Stop()

Description

Prematurely stops the tickless mode.

Prototype

void OS_TICKLESS_Stop(void);

Additional information

The tickless mode is stopped immediately even when no time-scheduled action is due.

OS_TICKLESS_Stop() calls the callback function registered when tickless mode was en-

abled.

311 CHAPTER 15 Tickless support

15.3.4 Frequently Asked Questions

Q: Can I use embOS without tickless support?

A: Yes, you can use embOS without tickless support. No changes to your project are

required.

Q: What hardware-dependent functions must be implemented and where?

A: OS_Idle() must be modified and the callback function must be implemented.

OS_Idle() is part of the RTOSInit.c file. We suggest to implement the callback function

in the same file.

Q: What triggers the callback function?

A: The callback function is executed once from the scheduler when the tickless operation

ends and normal operation resumes.

312 CHAPTER 15 Peripheral power control

15.4 Peripheral power control

The embOS peripheral power control is used to determine if a peripheral’s clock or its power

supply can be switched off to save power.

It includes three functions: OS_POWER_GetMask(), OS_POWER_UsageInc() and OS_POW-

ER_UsageDec(). These functions can be used to add peripheral power control to any em-

bOS start project.

If a peripheral gets initialized a call to OS_POWER_UsageInc() increments a specific entry in

the power management counter to signal that it is in use. When a peripheral is no longer

in use, a call to OS_POWER_UsageDec() decrements this counter. Within OS_Idle() a call of

OS_POWER_GetMask() generates a bit mask which describes which clock or power supply is

in use, and which is not and may therefore be switched off.

15.4.1 API functions

Routine Description

main

Task

ISR

Timer

Idle

OS_POWER_GetMask() Retrieves the power management counter. ● ● ● ● ●

OS_POWER_UsageDec() Decrements the power management

counter(s). ●●●●●

OS_POWER_UsageInc() Increments the power management counter(s). ● ● ● ● ●

313 CHAPTER 15 Peripheral power control

15.4.1.1 OS_POWER_GetMask()

Description

Retrieves the power management counter.

Prototype

OS_UINT OS_POWER_GetMask(void);

Return value

A bit mask which describes whether a peripheral is in use or not.

Additional information

This function generates a bit mask from the power management counter it retrieves. The

bit mask describes which peripheral is in use and which one can be turned off. Switching

off a peripheral can be done by writing this mask into the specific register. Please refer to

the Example for additional information.

314 CHAPTER 15 Peripheral power control

15.4.1.2 OS_POWER_UsageDec()

Description

Decrements the power management counter(s).

Prototype

void OS_POWER_UsageDec(OS_UINT Index);

Parameters

Parameter Description

Index

Contains a mask with bits set for those counters which

should be updated. (Bit 0 => Counter 0) The debug version

checks for underflow, overflow and undefined counter num-

ber.

Additional information

When a peripheral is no longer in use this function is called to mark the peripheral as unused

and signal that it can be switched off.

315 CHAPTER 15 Peripheral power control

15.4.1.3 OS_POWER_UsageInc()

Description

Increments the power management counter(s).

Prototype

void OS_POWER_UsageInc(OS_UINT Index);

Parameters

Parameter Description

Index

Contains a mask with bits set for those counters which

should be updated. (Bit 0 => Counter 0) The debug version

checks for underflow, overflow and undefined counter num-

ber.

Additional information

When a peripheral is in use this function is called to mark the peripheral as in use.

316 CHAPTER 15 Peripheral power control

15.4.2 Example

This is an example for the peripheral power control. As it depends on the used hardware,

its implementation is fictional: A, B and C are used to represent arbitrary peripherals.

#define OS_POWER_USE_A (1 << 0) // peripheral "A"

#define OS_POWER_USE_B (1 << 1) // peripheral "B"

#define OS_POWER_USE_C (1 << 2) // peripheral "C"

#define OS_POWER_USE_ALL (OS_POWER_USE_A | OS_POWER_USE_B | OS_POWER_USE_C)

In the following function the peripherals A and C have been initialized and were marked in-

use by a call to OS_POWER_UsageInc():

void _InitAC(void) {

...

OS_POWER_UsageInc(OS_POWER_USE_A); // Mark "A" as used

OS_POWER_UsageInc(OS_POWER_USE_C); // Mark "C" as used

...

}

After some time, C will not be used any more and can therefore be marked as unused by

a call to OS_POWER_UsageDec():

void _WorkDone(void) {

...

OS_POWER_UsageDec(OS_POWER_USE_C); // Mark "C" as unused

...

}

While in OS_Idle(), a call to OS_POWER_GetMask() retrieves a bit mask from the power

management counter. That bitmask subsequently is used to modify the corresponding bits

of a control register, leaving only those bits set that represent a peripheral which is in-use.

void OS_Idle(void) { // Idle loop: No task is ready to execute

OS_UINT PowerMask;

OS_U16 ClkControl;

// Initially disable interrupts

OS_INT_IncDI();

// Examine which peripherals may be switched off

PowerMask = OS_POWER_GetMask();

// Store the content of CTRLREG and clear all OS_POWER_USE related bits

ClkControl = CTRLREG & ~OS_POWER_USE_ALL;

// Set only bits for used peripherals and write them to the specific register

// In this case only "A" is marked as used, so "C" gets switched off

CTRLREG = ClkControl | PowerMask;

// Re-enable interrupts

OS_INT_DecRI();

for (;;) {

_do_nothing();

};

}

Chapter 16

Heap Type Memory

Management

318 CHAPTER 16 Introduction

16.1 Introduction

ANSI C offers some basic dynamic memory management functions. These are malloc, free,

and realloc. Unfortunately, these routines are not thread-safe, unless a special thread-safe

implementation exists in the compiler runtime libraries; they can only be used from one

task or by multiple tasks if they are called sequentially. Therefore, embOS offer thread

safe variants of these routines. These variants have the same names as their ANSI coun-

terparts, but are prefixed OS_HEAP_; they are called OS_HEAP_malloc(), OS_HEAP_free(),

OS_HEAP_realloc(). The thread-safe variants that embOS offers use the standard ANSI

routines, but they guarantee that the calls are serialized using a mutex.

If heap memory management is not supported by the standard C libraries, embOS heap

memory management is not implemented.

Heap type memory management is part of the embOS libraries. It does not use any re-

sources if it is not referenced by the application (that is, if the application does not use any

memory management API function).

Note that another aspect of these routines may still be a problem: the memory used for

the functions (known as heap) may fragment. This can lead to a situation where the total

amount of memory is sufficient, but there is not enough memory available in a single block

to satisfy an allocation request.

This API is not available in embOS library mode OS_LIBMODE_SAFE.

Example

void HPTask(void) {

OS_U32* p;

while (1) {

p = (OS_U32*)OS_HEAP_malloc(4);

*p = 42;

OS_HEAP_free(p);

}

void LPTask(void) {

OS_U16* p;

while (1) {

p = (OS_U16*)OS_HEAP_malloc(2);

*p = 0;

OS_HEAP_free(p);

}

319 CHAPTER 16 API functions

16.2 API functions

Routine Description

main

Task

ISR

Timer

OS_HEAP_free() Frees a block of memory previously allocated. ● ●

OS_HEAP_malloc() Allocates a block of memory on the heap. ● ●

OS_HEAP_realloc() Changes the allocation size. ● ●

320 CHAPTER 16 API functions

16.2.1 OS_HEAP_free()

Description

Frees a block of memory previously allocated.

This is the thread safe free() variant.

Prototype

void OS_HEAP_free(void* pMemBlock);

Parameters

Parameter Description

pMemBlock Pointer to a memory block previously allocated with

OS_HEAP_malloc().

Example

void UseHeapMem(void) {

char* sText;

sText = (char*)OS_HEAP_malloc(20);

strcpy(sText, "Hello World");

printf(sText);

OS_HEAP_free(p);

}

321 CHAPTER 16 API functions

16.2.2 OS_HEAP_malloc()

Description

Allocates a block of memory on the heap.

This is the thread safe malloc() variant.

Prototype

void *OS_HEAP_malloc(unsigned int Size);

Parameters

Parameter Description

Size Size of the requested memory block in bytes.

Return value

Upon successful completion with size not equal zero, OS_HEAP_malloc() returns a pointer

to the allocated space. Otherwise, it returns a NULL pointer.

Example

void UseHeapMem(void) {

char* sText;

sText = (char*)OS_HEAP_malloc(20);

strcpy(sText, "Hello World");

printf(sText);

OS_HEAP_free(p);

}

322 CHAPTER 16 API functions

16.2.3 OS_HEAP_realloc()

Description

Changes the allocation size.

This is the thread safe realloc() variant.

Prototype

void *OS_HEAP_realloc(void* pMemBlock,

unsigned int NewSize);

Parameters

Parameter Description

pMemBlock Pointer to a memory block previously allocated with

OS_HEAP_malloc().

NewSize New size for the memory block in bytes.

Return value

Upon successful completion, OS_HEAP_realloc() returns a pointer to the reallocated mem-

ory block. Otherwise, it returns a NULL pointer.

Example

void UseHeapMem(void) {

char* sText;

sText = (char*)OS_HEAP_malloc(10);

strcpy(sText, "Hello");

printf(sText);

sText = (char*)OS_HEAP_realloc(sText, 20);

strcpy(sText, "Hello World");

printf(sText);

OS_HEAP_free(p);

}

Chapter 17

Fixed Block Size Memory Pool

324 CHAPTER 17 Introduction

17.1 Introduction

Fixed block size memory pools contain a specific number of fixed-size blocks of memory.

The location in memory of the pool, the size of each block, and the number of blocks are

set at runtime by the application via a call to the OS_MEMPOOL_Create() function. The

advantage of fixed memory pools is that a block of memory can be allocated from within

any task in a very short, determined period of time.

Example

#include "RTOS.h"

#include <string.h>

#include <stdio.h>

#define BLOCK_SIZE (16)

#define NUM_BLOCKS (16)

#define POOL_SIZE (NUM_BLOCKS* BLOCK_SIZE)

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task-control-blocks

static OS_MEMPOOL MEMF;

static OS_U8 aPool[POOL_SIZE];

static void HPTask(void) {

char* a;

while (1) {

// Request one memory block

a = OS_MEMPOOL_AllocBlocked(&MEMF);

// Work with memory block

strcpy(a, "Hello World\n");

printf(a);

OS_MEMPOOL_FreeEx(&MEMF, a); // Release memory block

OS_TASK_Delay (10);

}

static void LPTask(void) {

char* b;

while (1) {

// Request one memory block when available in max. next 10 system ticks

b = OS_MEMPOOL_AllocTimed(&MEMF, 10);

if (b != 0) {

// Work with memory block

b[0] = 0x12;

b[1] = 0x34;

// Releae memory block

OS_MEMPOOL_FreeEx(&MEMF, b);

}

OS_TASK_Delay (50);

}

int main(void) {

OS_Init(); // Initialize embOS

325 CHAPTER 17 Introduction

OS_InitHW(); // Initialize hardware for embOS

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

// Create [NUM_BLOCKS] blocks with a size of [BLOCK_SIZE] each

OS_MEMPOOL_Create(&MEMF, aPool, NUM_BLOCKS, BLOCK_SIZE);

OS_Start(); // Start multitasking

return 0;

}

326 CHAPTER 17 API functions

17.2 API functions

Routine Description

main

Task

ISR

Timer

OS_MEMPOOL_Alloc() Requests allocation of a memory

block. ●●●●

OS_MEMPOOL_AllocBlocked() Allocates a memory block from pool. ● ●

OS_MEMPOOL_AllocTimed() Allocates a memory block from pool

with a timeout. ● ●

OS_MEMPOOL_Create() Creates and initializes a fixed block

size memory pool. ● ●

OS_MEMPOOL_Delete() Deletes a fixed block size memory

pool. ● ●

OS_MEMPOOL_Free() Releases a memory block that was

previously allocated. ●●●●

OS_MEMPOOL_FreeEx() Releases a memory block that was

previously allocated. ●●●●

OS_MEMPOOL_GetBlockSize() Returns the size of a single memory

block in the pool. ●●●●

OS_MEMPOOL_GetMaxUsed() Returns maximum number of blocks in

a pool that have been used simultane-

ously since creation of the pool.

●●●●

OS_MEMPOOL_GetNumBlocks() Returns the total number of memory

blocks in the pool. ●●●●

OS_MEMPOOL_GetNumFreeBlocks() Returns the number of free memory

blocks in the pool. ●●●●

OS_MEMPOOL_IsInPool()

Information routine to examine

whether a memory block reference

pointer belongs to the specified mem-

ory pool.

●●●●

327 CHAPTER 17 API functions

17.2.1 OS_MEMPOOL_Alloc()

Description

Requests allocation of a memory block. Continues execution without blocking.

Prototype

void *OS_MEMPOOL_Alloc(OS_MEMPOOL* pMEMF);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

Return value

≠ NULL Pointer to the allocated block.

= NULL If no block has been allocated.

Additional information

The calling task is never suspended by calling OS_MEMPOOL_Alloc(). The returned pointer

must be delivered to OS_MEMPOOL_FreeEx() as parameter to free the memory block. The

pointer must not be modified.

Example

static OS_MEMPOOL _MemPool;

void Task(void) {

void* pData;

pData = OS_MEMPOOL_Alloc(&_MemPool, 0);

if (pData != NULL) {

// Success: Work with the allocated memory.

} else {

// Failed: Do something else.

}

328 CHAPTER 17 API functions

17.2.2 OS_MEMPOOL_AllocBlocked()

Description

Allocates a memory block from pool. Suspends until memory is available.

Prototype

void *OS_MEMPOOL_AllocBlocked(OS_MEMPOOL* pMEMF);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

Return value

Pointer to the allocated memory block.

Additional information

If there is no free memory block in the pool, the calling task is suspended until a memory

block becomes available. The retrieved pointer must be delivered to OS_MEMPOOL_FreeEx()

as a parameter to free the memory block. The pointer must not be modified.

Example

Please refer to the example in the Introduction on page 324.

329 CHAPTER 17 API functions

17.2.3 OS_MEMPOOL_AllocTimed()

Description

Allocates a memory block from pool with a timeout. Suspends until memory is available

or a timeout occurs.

Prototype

void *OS_MEMPOOL_AllocTimed(OS_MEMPOOL* pMEMF,

OS_TIME Timeout);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

Timeout

Time limit before timeout, given in system ticks. The data

type OS_TIME is defined as an integer, therefore valid values

are:

0 ≤ TimeOut ≤ 215 - 1 = 0x7FFF for 8/16 bit CPUs.

0 ≤ TimeOut ≤ 231 - 1 = 0x7FFFFFFF for 32 bit CPUs.

Return value

= NULL No memory block could be allocated within the specified time.

≠ NULL Pointer to the allocated memory block.

Additional information

If there is no free memory block in the pool, the calling task is suspended until a memory

block becomes available or the timeout has expired. The returned pointer must be delivered

to OS_MEMPOOL_FreeEx() as parameter to free the memory block. The pointer must not

be modified.

When the calling task is blocked by higher priority tasks for a period longer than the timeout

value, it may happen that the memory block becomes available after the timeout expired,

but before the calling task is resumed. Anyhow, the function returns with timeout, because

the memory block was not available within the requested time.

Example

static OS_MEMPOOL _MemPool;

void Task(void) {

void* pData;

pData = OS_MEMPOOL_AllocTimed(&_MemPool, 20, 0);

if (pData != NULL) {

// Success: Work with the allocated memory.

} else {

// Failed: Do something else.

}

330 CHAPTER 17 API functions

17.2.4 OS_MEMPOOL_Create()

Description

Creates and initializes a fixed block size memory pool.

Prototype

void OS_MEMPOOL_Create(OS_MEMPOOL* pMEMF,

void* pPool,

OS_UINT NumBlocks,

OS_UINT BlockSize);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

pPool Pointer to memory to be used for the memory pool. Required

size is: NumBlocks * BlockSize.

NumBlocks Number of blocks in the pool.

BlockSize Size in bytes of one block.

Additional information

Before using any memory pool, it must be created. A debug build of libraries keeps track

of created and deleted memory pools. The release and stack-check builds do not. The

maximum number of blocks and the maximum block size is for 16Bit CPUs 0x7FFF and for

32Bit CPUs 0x7FFFFFFF.

Example

#define NUM_BLOCKS (16)

#define BLOCK_SIZE (16)

#define POOL_SIZE (NUM_BLOCKS * BLOCK_SIZE)

OS_U8 aPool[POOL_SIZE];

OS_MEMPOOL MyMEMF;

void Init(void) {

// Create 16 Blocks with size of 16 Bytes

OS_MEMPOOL_Create(&MyMEMF, aPool, NUM_BLOCKS, BLOCK_SIZE);

}

331 CHAPTER 17 API functions

17.2.5 OS_MEMPOOL_Delete()

Description

Deletes a fixed block size memory pool. After deletion, the memory pool and memory blocks

inside this pool can no longer be used.

Prototype

void OS_MEMPOOL_Delete(OS_MEMPOOL* pMEMF);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

Additional information

This routine is provided for completeness. It is not used in the majority of applications

since there is no need to dynamically create/delete memory pools. For most applications,

it is suggested to have a static memory pool design: memory pools are created at startup

(before calling OS_Start()) and never get deleted. A debug build of embOS will explicitly

mark a memory pool as deleted.

332 CHAPTER 17 API functions

17.2.6 OS_MEMPOOL_Free()

Description

Releases a memory block that was previously allocated. The memory pool does not need

to be denoted.

Prototype

void OS_MEMPOOL_Free(void* pMemBlock);

Parameters

Parameter Description

pMemBlock Pointer to the control data structure of the memory pool.

Additional information

This function may be used instead of OS_MEMPOOL_FreeEx(). It has the advantage that only

one parameter is needed since embOS will automatically determine the associated memory

pool. The memory block becomes available for other tasks waiting for a memory block from

the associated pool, which may cause a subsequent task switch.

Example

void Task(void) {

void* pMem;

...

OS_MEMPOOL_Free(pMem);

...

}

333 CHAPTER 17 API functions

17.2.7 OS_MEMPOOL_FreeEx()

Description

Releases a memory block that was previously allocated.

Prototype

void OS_MEMPOOL_FreeEx(OS_MEMPOOL* pMEMF,

void* pMemBlock);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

pMemBlock Pointer to memory block to free.

Additional information

The memory block becomes available for other tasks waiting for a memory block from the

associated pool, which may cause a subsequent task switch.

Example

Please refer to the example in the Introduction on page 324.

334 CHAPTER 17 API functions

17.2.8 OS_MEMPOOL_GetBlockSize()

Description

Returns the size of a single memory block in the pool.

Prototype

int OS_MEMPOOL_GetBlockSize(OS_CONST_PTR OS_MEMPOOL *pMEMF);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

Return value

Size in bytes of a single memory block in the specified memory pool. This is the value of

the parameter when the memory pool was created.

Example

static OS_MEMPOOL _MemPool;

void PrintBlockSize(void) {

int Size;

Size = OS_MEMPOOL_GetBlockSize(&_MemPool);

printf("Block Size: %d\n", Size);

}

335 CHAPTER 17 API functions

17.2.9 OS_MEMPOOL_GetMaxUsed()

Description

Returns maximum number of blocks in a pool that have been used simultaneously since

creation of the pool.

Prototype

int OS_MEMPOOL_GetMaxUsed(OS_CONST_PTR OS_MEMPOOL *pMEMF);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

Return value

Maximum number of blocks in the specified memory pool that were used simultaneously

since the pool was created.

Example

static OS_MEMPOOL _MemPool;

void PrintMemoryUsagePeak(void) {

int BlockCnt, UsedBlocks, ;

void* pData;

pData = OS_MEMPOOL_AllocBlocked(&_MemPool, 0);

BlockCnt = OS_MEMPOOL_GetNumBlocks(&_MemPool);

UsedBlocks = OS_MEMPOOL_GetMaxUsed(&_MemPool);

if (UsedBlocks != 0) {

printf("Max used Memory: %d%%\n", (int)

(((float)UsedBlocks / BlockCnt) * 100));

} else {

printf("Max used Memory: 0%%");

}

336 CHAPTER 17 API functions

17.2.10 OS_MEMPOOL_GetNumBlocks()

Description

Returns the total number of memory blocks in the pool.

Prototype

int OS_MEMPOOL_GetNumBlocks(OS_CONST_PTR OS_MEMPOOL *pMEMF);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of memory pool.

Return value

Returns the number of blocks in the specified memory pool. This is the value that was given

as parameter during creation of the memory pool.

Please refer to the example of OS_MEMPOOL_GetMaxUsed() or OS_MEMPOOL_GetNumFree-

Blocks().

337 CHAPTER 17 API functions

17.2.11 OS_MEMPOOL_GetNumFreeBlocks()

Description

Returns the number of free memory blocks in the pool.

Prototype

int OS_MEMPOOL_GetNumFreeBlocks(OS_CONST_PTR OS_MEMPOOL *pMEMF);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

Return value

The number of free blocks currently available in the specified memory pool.

Example

static OS_MEMPOOL _MemPool;

void PrintMemoryUsage(void) {

int BlockCnt;

int UnusedBlocks;

void* pData;

pData = OS_MEMPOOL_AllocBlocked(&_MemPool, 0);

BlockCnt = OS_MEMPOOL_GetNumBlocks(&_MemPool);

UnusedBlocks = OS_MEMPOOL_GetNumFreeBlocks(&_MemPool);

if (UnusedBlocks != 0) {

printf("Used Memory: %d%%\n", 100 - (int)

(((float)UnusedBlocks / BlockCnt) * 100));

} else {

printf("Used Memory: 0%%");

}

338 CHAPTER 17 API functions

17.2.12 OS_MEMPOOL_IsInPool()

Description

Information routine to examine whether a memory block reference pointer belongs to the

specified memory pool.

Prototype

OS_BOOL OS_MEMPOOL_IsInPool(OS_CONST_PTR OS_MEMPOOL *pMEMF,

OS_CONST_PTR void *pMemBlock);

Parameters

Parameter Description

pMEMF Pointer to the control data structure of the memory pool.

pMemBlock Pointer to a memory block that should be checked.

Return value

0 Pointer does not belong to the specified memory pool.

1 Pointer belongs to the specified memory pool.

Example

static OS_MEMPOOL _MemPool;

void CheckPointerLocation(OS_MEMPOOL* pMEMF, void* Pointer) {

if (OS_MEMPOOL_IsInPool(pMEMF, Pointer) == 0) {

printf("Pointer doesn't belong to the specified memory pool.\n");

} else {

printf("Pointer belongs to the specified memory pool.\n");

}

Chapter 18

System Tick

340 CHAPTER 18 Introduction

18.1 Introduction

This chapter explains the concept of the system tick, which is used as a time base for

embOS.

Typically, a hardware timer is used to generate periodic interrupts which are then utilized

as a time base for embOS. To do so, the timer’s according interrupt service routine must

call one of the embOS tick handlers.

embOS offers different tick handlers with different functionality, and also provides the

means to optionally call a user-defined hook function from within these tick handlers.

The used hardware timer usually is initialized within OS_InitHW(), which is delivered with

the respective embOS start project’s RTOSInit.c. This also includes the interupt handler

that is called by the hardware timer interrupt. Modifications to this initialization and the

respective interrupt handler are required when a different hardware timer should be used

(see Using a different timer to generate tick interrupts for embOS on page 461).

Tick handler

The interrupt service routine used as a time base must call one of the embOS tick handlers.

The reason why there are different tick handlers is simple: They differ in capabilities, code

size and execution speed. Most applications use the standard tick handler OS_TICK_Han-

dle(), which increments the tick count by one each time it is called. This tick handler is

small and efficient, but it cannot handle situations in which the interrupt rate differs from

the tick rate. OS_TICK_HandleEx() is capable of handling even fractional interrupt rates,

such as 1.6 interrupts per tick.

18.2 API functions

Routine Description

main

Task

ISR

Timer

OS_TICK_Config() Configures the tick to interrupt ratio. ● ●

OS_TICK_Handle() Default embOS timer tick handler. ●

OS_TICK_HandleEx() Alternate tick handler that may be used instead

of the default tick handler. ●

OS_TICK_HandleNoHook() Speed-optimized embOS timer tick handler

without hook functionality. ●

341 CHAPTER 18 API functions

18.2.1 OS_TICK_Config()

Description

Configures the tick to interrupt ratio. The default tick handler, OS_TICK_Handle(), assumes

a 1:1 ratio, meaning one interrupt increments the tick count (OS_Global.Time) by one.

For other ratios, OS_TICK_HandleEx() must to be used instead of the default handler and

the tick to interrupt ratio must be configured through a call to OS_TICK_Config(). Since this

must be done before the embOS timer is started, it is suggested to call OS_TICK_Config()

during OS_InitHW().

Prototype

void OS_TICK_Config(unsigned FractPerInt,

unsigned FractPerTick);

Parameters

Parameter Description

FractPerInt Number of fractions per interrupt.

FractPerTick Number of fractions per tick.

Additional information

FractPerInt/FractPerTick = Time between two tick interrupts/Time for one tick.

Fractional values are supported. For example, a 1 msec tick can be used even when an

interrupt is generated every 1.6 msec only. In that case, FractPerInt and FractPerTick

must be:

FractPerInt = 16;

FractPerTick = 10;

FractPerInt = 8;

FractPerTick = 5;

Example

OS_TICK_Config(2, 1); // 500 Hz interrupts (2 msec), 1 msec tick

OS_TICK_Config(8, 5); // Interrupts once per 1.6 msec, 1 msec tick

OS_TICK_Config(1, 10); // 10 kHz interrupts (0.1 msec), 1 msec tick

OS_TICK_Config(1, 1); // 10 kHz interrupts (0.1 msec), 0.1 msec tick

OS_TICK_Config(1, 100); // 10 kHz interrupts (0.1 msec), 1 usec tick

342 CHAPTER 18 API functions

18.2.2 OS_TICK_Handle()

Description

Default embOS timer tick handler. It assumes a 1:1 tick to interrupt ratio, i.e. one interrupt

increments the tick count by one.

Prototype

void OS_TICK_Handle(void);

Additional information

The embOS tick handler must not be called by the application, but must be called from the

hardware timer interrupt handler. OS_INT_Enter() or OS_INT_EnterNestable() must be

called before calling the embOS tick handler.

If any tick hook functions have been added by the application (see Hooking into the system

tick on page 345), these will be called by OS_TICK_Handle().

Example

__interrupt void SysTick_Handler(void) {

OS_INT_EnterNestable();

OS_TICK_Handle();

OS_INT_LeaveNestable();

}

343 CHAPTER 18 API functions

18.2.3 OS_TICK_HandleEx()

Description

Alternate tick handler that may be used instead of the default tick handler. It may be used

in situations in which the interrupt rate differs from the tick rate.

Prototype

void OS_TICK_HandleEx(void);

Additional information

The embOS tick handler must not be called by the application, but must be called from the

hardware timer interrupt handler. OS_INT_Enter() or OS_INT_EnterNestable() must be

called before calling the embOS tick handler.

If any tick hook functions have been added by the application (see Hooking into the system

tick on page 345), these will be called by OS_TICK_HandleEx().

Refer to OS_TICK_Config() for information on how to configure the tick to interrupt ratio

for OS_TICK_HandleEx().

Example

__interrupt void SysTick_Handler(void) {

OS_INT_EnterNestable();

OS_TICK_HandleEx();

OS_INT_LeaveNestable();

}

344 CHAPTER 18 API functions

18.2.4 OS_TICK_HandleNoHook()

Description

Speed-optimized embOS timer tick handler without hook functionality.

Prototype

void OS_TICK_HandleNoHook(void);

Additional information

The embOS tick handler must not be called by the application, it is only called from the

system tick interrupt handler. OS_INT_Enter() or OS_INT_EnterNestable() must be called

before calling the embOS tick handler.

OS_TICK_HandleNoHook() will not call any tick hook functions that may have been added

by the application (see Hooking into the system tick on page 345).

Example

__interrupt void SysTick_Handler(void) {

OS_INT_EnterNestable();

OS_TICK_HandleNoHook();

OS_INT_LeaveNestable();

}

345 CHAPTER 18 Hooking into the system tick

18.3 Hooking into the system tick

There are various situations in which it can be desirable to call a function from the tick

handler. Some examples are:

• Watchdog update

• Periodic status check

• Periodic I/O update

The same functionality can be achieved with a high-priority task or a software timer with

one-tick period time.

Advantage of using a hook function

Using a hook function is much faster than performing a task switch or activating a software

timer because the hook function is directly called from the embOS timer interrupt handler

and does not cause a context switch.

18.4 API functions

Routine Description

main

Task

ISR

Timer

OS_TICK_AddHook() Adds a tick hook handler. ● ●

OS_TICK_RemoveHook() Removes a tick hook handler. ● ●

346 CHAPTER 18 API functions

18.4.1 OS_TICK_AddHook()

Description

Adds a tick hook handler.

Prototype

void OS_TICK_AddHook(OS_TICK_HOOK* pHook,

OS_TICK_HOOK_ROUTINE* pfUser);

Parameters

Parameter Description

pHook Pointer to a structure of OS_TICK_HOOK.

pfUser Pointer to an OS_TICK_HOOK_ROUTINE function.

Additional information

The hook function is called directly from the interrupt handler. The function therefore should

execute as quickly as possible. The function called by the tick hook must not re-enable

interrupts.

Example

static OS_TICK_HOOK _Hook;

void HookRoutine(void) {

// Do something...

}

int main(void) {

...

OS_TICK_AddHook(&_Hook, HookRoutine);

...

}

347 CHAPTER 18 API functions

18.4.2 OS_TICK_RemoveHook()

Description

Removes a tick hook handler.

Prototype

void OS_TICK_RemoveHook(OS_CONST_PTR OS_TICK_HOOK *pHook);

Parameters

Parameter Description

pHook Pointer to a structure of OS_TICK_HOOK.

Additional information

The function may be called to dynamically remove a tick hook function installed by a call

to OS_TICK_AddHook().

Example

static OS_TICK_HOOK _Hook;

void Task(void) {

...

OS_TICK_RemoveHook(&_Hook);

...

}

348 CHAPTER 18 Disabling the system tick

18.5 Disabling the system tick

With many MCUs, power consumption may be reduced by using the embOS tickless support.

Please refer to Tickless support on page 304 for further information.

Chapter 19

Debugging

350 CHAPTER 19 Runtime application errors

19.1 Runtime application errors

Many application errors can be detected during runtime.

These are for example:

• Invalid usage of embOS API

• Usage of uninitialized embOS data structures

• Invalid pointers

• Stack overflow

Which runtime errors can be detected depends on how many checks are performed. Un-

fortunately, additional checks cost memory and performance (it is not that significant, but

there is a difference). Not all embOS library modes include the debug and stack check code.

For example OS_LIBMODE_DP includes the debug and stack check, whereas OS_LIBMODE_R

does not contain any debug or stack check code.

Note

If an application error is detected and OS_Error() is called, do not switch to another

embOS library mode which does not contain the debug checks. While doing so avoids

calls to OS_Error(), it does not fix the original application error.

When embOS detects a runtime error, it calls the following routine:

void OS_Error(OS_STATUS ErrCode);

This routine is shipped as source code as part of the module OS_Error.c. Although this

function is named OS_Error(), it does not show embOS erros but application errors. It

simply disables further task switches and then, after re-enabling interrupts, loops forever

as follows:

Example

// Run time error reaction

void OS_Error(OS_STATUS ErrCode) {

OS_TASK_EnterRegion(); // Avoid further task switches

OS_Global.Counters.DI = 0u; // Allow interrupts so we can communicate

OS_INT_Enable();

OS_Status = ErrCode;

while (OS_Status) {

// Endless loop may be left by setting OS_Status to 0

}

If you are using embOSView, you can see the value and meaning of OS_Status in the

system variable window.

When using a debugger, you should set a breakpoint at the beginning of this routine or

simply stop the program after a failure. The error code is passed to the function as a

parameter. You should add OS_Status to your watch window.

You can modify the routine to accommodate to your own hardware; this could mean that

your target hardware sets an error-indicating LED or shows a small message on the display.

Note

When modifying the OS_Error() routine, the first statement needs to be the disabling

of the scheduler via OS_TASK_EnterRegion(); the last statement needs to be the

infinite loop.

351 CHAPTER 19 Runtime application errors

If you look at the OS_Error() routine, you will see that it is more complicated than neces-

sary. The actual error code is assigned to the global variable OS_Status. The program then

waits for this variable to be reset. Simply reset this variable to 0 using your debugger, and

you can easily step back to the program sequence causing the problem. Most of the time,

looking at this part of the program will make the problem clear.

OS_DEBUG_LEVEL

The preprocessor symbol OS_DEBUG_LEVEL defines the embOS debug level. The default

value is 1. With higher debug levels more debug code is included. This define can be changed

with the embOS source code only.

19.1.1 List of error codes

Value Define Explanation

0OS_OK No error, everything ok.

100 OS_ERR_ISR_INDEX Index value out of bounds during interrupt

controller initialization or interrupt installa-

tion.

101 OS_ERR_ISR_VECTOR Default interrupt handler called, but inter-

rupt vector not initialized.

102 OS_ERR_ISR_PRIO Wrong interrupt priority.

103 OS_ERR_WRONG_STACK Wrong stack used before main().

104 OS_ERR_ISR_NO_HANDLER No interrupt handler was defined for this

interrupt.

105 OS_ERR_TLS_INIT OS_TLS_Init() called multiple times from

one task.

106 OS_ERR_MB_BUFFER_SIZE For 16bit CPUs, the maximum buffer size

for a mailbox (64KB) exceeded.

116 OS_ERR_EXTEND_CONTEXT OS_ExtendTaskContext() called multiple

times from one task.

118 OS_ERR_INTERNAL OS_ChangeTask() called without Region

Counter set (or other internal error).

119 OS_ERR_IDLE_RETURNS OS_Idle() must not return.

120 OS_ERR_STACK Task stack overflow or invalid task stack.

121 OS_ERR_SEMAPHORE_OVERFLOW Semaphore value overflow.

122 OS_ERR_POWER_OVER Counter overflows when calling OS_POW-

ER_UsageInc().

123 OS_ERR_POWER_UNDER Counter underflows when calling OS_POW-

ER_UsageDec().

124 OS_ERR_POWER_INDEX Index to high, exceeds (OS_POW-

ER_NUM_COUNTERS - 1).

125 OS_ERR_SYS_STACK System stack overflow.

126 OS_ERR_INT_STACK Interrupt stack overflow.

128 OS_ERR_INV_TASK Task control block invalid, not initialized or

overwritten.

129 OS_ERR_INV_TIMER Timer control block invalid, not initialized

or overwritten.

130 OS_ERR_INV_MAILBOX Mailbox control block invalid, not initialized

or overwritten.

132 OS_ERR_INV_SEMAPHORE Control block for semaphore invalid, not

initialized or overwritten.

352 CHAPTER 19 Runtime application errors

Value Define Explanation

133 OS_ERR_INV_MUTEX Control block for mutex invalid, not initial-

ized or overwritten.

135 OS_ERR_MAILBOX_NOT1

One of the following 1-byte mailbox func-

tions has been used on a multibyte mail-

box: OS_MAILBOX_Get1(), OS_MAIL-

BOX_GetBlocked1(), OS_MAILBOX_Get-

Timed1(), OS_MAILBOX_Put1(), OS_MAIL-

BOX_PutBlocked1(), OS_MAILBOX_Put-

Front1(), OS_MAILBOX_PutFront-

Blocked1() or OS_MAILBOX_PutTimed1().

•OS_MAILBOX_Get1()

•OS_MAILBOX_GetBlocked1()

•OS_MAILBOX_GetTimed1()

•OS_MAILBOX_Put1()

•OS_MAILBOX_PutBlocked1()

•OS_MAILBOX_PutFront1()

•OS_MAILBOX_PutFrontBlocked1()

•OS_MAILBOX_PutTimed1()

136 OS_ERR_MAILBOX_DELETE OS_MAILBOX_Delete() was called on a

mailbox with waiting tasks.

137 OS_ERR_SEMAPHORE_DELETE OS_SEMAPHORE_Delete() was called on a

semaphore with waiting tasks.

138 OS_ERR_MUTEX_DELETE OS_MUTEX_Delete() was called on a mutex

which is claimed by a task.

140 OS_ERR_MAIL-

BOX_NOT_IN_LIST

The mailbox is not in the list of mail-boxes

as expected. Possible reasons may be that

one mailbox data structure was overwrit-

ten.

142 OS_ERR_TASKLIST_CORRUPT The OS internal task list is destroyed.

143 OS_ERR_QUEUE_INUSE Queue in use.

144 OS_ERR_QUEUE_NOT_INUSE Queue not in use.

145 OS_ERR_QUEUE_INVALID Queue invalid.

146 OS_ERR_QUEUE_DELETE A queue was deleted by a call of

OS_QUEUE_Delete() while tasks are wait-

ing at the queue.

147 OS_ERR_MB_INUSE Mailbox in use.

148 OS_ERR_MB_NOT_INUSE Mailbox not in use.

149 OS_ERR_MESSAGE_SIZE_ZERO Attempt to store a message with size of

zero.

150 OS_ERR_UNUSE_BEFORE_USE OS_MUTEX_Unlock() has been called on a

mutex hasn’t been locked before.

151 OS_ERR_LEAVEREGION_BE-

FORE_ENTERREGION OS_TASK_LeaveRegion() has been called

before OS_TASK_EnterRegion().

152 OS_ERR_LEAVEINT Error in OS_INT_Leave().

153 OS_ERR_DICNT

The interrupt disable counter ( OS_Glob-

al.Counters.Cnt.DI ) is out of range

(0-15). The counter is affected by the fol-

lowing API calls:

•OS_INT_IncDI()

•OS_INT_DecRI()

•OS_INT_Enter()

•OS_INT_Leave()

353 CHAPTER 19 Runtime application errors

Value Define Explanation

154 OS_ERR_INTERRUPT_DISABLED OS_TASK_Delay() or OS_TASK_DelayUn-

til() called from inside a critical region

with interrupts disabled.

155

OS_ER-

R_TASK_ENDS_WITHOUT_TER-

MINATE

Task routine returns without 0S_TASK_Ter-

minate().

156 OS_ERR_RESOURCE_OWNER OS_MUTEX_Unlock() has been called from

a task which does not own the mutex.

157 OS_ERR_REGIONCNT The Region counter overflows (>255).

158 OS_ERR_DELAYUS_INTERRUP-

T_DISABLED OS_TASK_Delayus() called with interrupts

disabled.

160 OS_ERR_ILLEGAL_IN_ISR

Illegal function call in an interrupt service

routine: A routine that must not be called

from within an ISR has been called from

within an ISR.

161 OS_ERR_ILLEGAL_IN_TIMER

Illegal function call in a software timer: A

routine that must not be called from with-

in a software timer has been called from

within a timer.

162 OS_ERR_ILLEGAL_OUT_ISR Not a legal API outside interrupt.

163 OS_ERR_NOT_IN_ISR OS_INT_Enter() has been called, but CPU

is not in ISR state.

164 OS_ERR_IN_ISR OS_INT_Enter() has not been called, but

CPU is in ISR state.

165 OS_ERR_INIT_NOT_CALLED OS_Init() was not called.

166 OS_ERR_CPU_STATE_ISR_IL-

LEGAL embOS API called from ISR with high pri-

ority.

167 OS_ERR_CPU_STATE_ILLEGAL CPU runs in illegal mode.

168 OS_ERR_CPU_STATE_UNKNOWN CPU runs in unknown mode or mode could

not be read.

170 OS_ERR_2USE_TASK Task control block has been initialized by

calling a create function twice.

171 OS_ERR_2USE_TIMER Timer control block has been initialized by

calling a create function twice.

172 OS_ERR_2USE_MAILBOX Mailbox control block has been initialized

by calling a create function twice.

174 OS_ERR_2USE_SEMAPHORE Semaphore has been initialized by calling a

create function twice.

175 OS_ERR_2USE_MUTEX Mutex has been initialized by calling a cre-

ate function twice.

176 OS_ERR_2USE_MEMF Fixed size memory pool has been initial-

ized by calling a create function twice.

177 OS_ERR_2USE_QUEUE Queue has been initialized by calling a cre-

ate function twice.

178 OS_ERR_2USE_EVENT Event object has been initialized by calling

a create function twice.

179 OS_ERR_2USE_WATCHDOG Watchdog has been initialized by calling a

create function twice.

180 OS_ERR_NESTED_RX_INT OS_Rx interrupt handler for embOSView is

nested. Disable nestable interrupts.

354 CHAPTER 19 Runtime application errors

Value Define Explanation

185 OS_ERR_SPINLOCK_INV_CORE Invalid core ID specified for accessing a

OS_SPINLOCK_SW struct.

190 OS_ERR_MEMF_INV Fixed size memory block control structure

not created before use.

191 OS_ERR_MEMF_INV_PTR Pointer to memory block does not belong

to memory pool on Release.

192 OS_ERR_MEMF_PTR_FREE Pointer to memory block is already free

when calling OS_MEMPOOL_Release(). Pos-

sibly, same pointer was released twice.

193 OS_ERR_MEMF_RELEASE

OS_MEMPOOL_Release() was called for a

memory pool, that had no memory block

allocated (all available blocks were already

free before).

194 OS_ERR_MEMF_POOLADDR OS_MEMPOOL_Create() was called with a

memory pool base address which is not lo-

cated at a word aligned base address.

195 OS_ERR_MEMF_BLOCKSIZE OS_MEMPOOL_Create() was called with a

data block size which is not a multiple of

processors word size.

200 OS_ERR_SUSPEND_TOO_OFTEN Nested call of OS_TASK_Suspend() exceed-

ed OS_MAX_SUSPEND_CNT.

201 OS_ERR_RESUME_BE-

FORE_SUSPEND OS_TASK_Resume() called on a task that

was not suspended.

202 OS_ERR_TASK_PRIORITY

OS_TASK_Create() was called with a task

priority which is already assigned to an-

other task. This error can only occur when

embOS was compiled without round-robin

support.

203 OS_ERR_TASK_PRIORITY_IN-

VALID The value 0 was used as task priority.

205 OS_ERR_TIMER_PERIOD_IN-

VALID The value 0 was used as timer period.

210 OS_ERR_EVENT_INVALID An OS_EVENT object was used before it was

created.

212 OS_ERR_EVENT_DELETE An OS_EVENT object was deleted with wait-

ing tasks.

220 OS_ERR_WAITLIST_RING This error should not occur. Please contact

the support.

221 OS_ERR_WAITLIST_PREV This error should not occur. Please contact

the support.

222 OS_ERR_WAITLIST_NEXT This error should not occur. Please contact

the support.

223 OS_ERR_TICKHOOK_INVALID Invalid tick hook.

224 OS_ERR_TICKHOOK_FUNC_IN-

VALID Invalid tick hook function.

225 OS_ERR_NOT_IN_REGION A function was called without declaring the

necessary critical region.

226 OS_ERR_ILLEGAL_IN_MAIN Not a legal API call from main().

227 OS_ERR_ILLEGAL_IN_TASK Not a legal API after OS_Start().

228 OS_ERR_ILLEGAL_AFTER_OSS-

TART Not a legal API after OS_Start().

355 CHAPTER 19 Runtime application errors

Value Define Explanation

230 OS_ERR_NON_ALIGNED_IN-

VALIDATE Cache invalidation needs to be cache line

aligned.

234 OS_ERR_HW_NOT_AVAILABLE Hardware unit is not implemented or en-

abled.

235 OS_ERR_NON_TIMERCY-

CLES_FUNC

Callback function for timer counter

value has not been set. Required by

OS_TIME_Getus().

236 OS_ERR_NON_TIMERINT-

PENDING_FUNC

Callback function for timer interrupt pend-

ing flag has not been set. Required by

OS_TIME_Getus().

240 OS_ERR_MPU_NOT_PRESENT MPU unit not present in the device.

241 OS_ERR_MPU_INVALID_REGION Invalid MPU region index number.

242 OS_ERR_MPU_INVALID_SIZE Invalid MPU region size.

243 OS_ERR_MPU_INVALID_PER-

MISSION Invalid MPU region permission.

244 OS_ERR_MPU_INVALID_ALIGN-

MENT Invalid MPU region alignment.

245 OS_ERR_MPU_INVALID_OBJECT OS object is directly accessible from the

task which is not allowed.

250 OS_ERR_CONFIG_OSSTOP OS_Stop() is called without using OS_Con-

figStop() before.

251 OS_ERR_OSSTOP_BUFFER Buffer is too small to hold a copy of the

main() stack.

253 OS_ERR_VERSION_MISMATCH OS library and RTOS have different version

numbers. Please ensure both are from the

same embOS shipment.

19.1.2 Application defined error codes

The embOS error codes begin at 100. The range 1 - 99 can be used for application defined

error codes. With it you can call OS_Error() with your own defined error code from your

application.

Example

#define OS_ERR_APPL (0x02u)

void UserAppFunc(void) {

int r;

r = DoSomething()

if (r == 0) {

OS_Error(OS_ERR_APPL)

}

356 CHAPTER 19 Human readable object identiﬁers

19.2 Human readable object identifiers

embOS objects like mailbox or semaphore are handled via separate control structures. Each

OS object is identified by the address of the according control structure. For debugging

purpose this address is displayed in external tools like embOSView or IDE RTOS plugins.

Tasks always have a human readable task name (except in OS_LIBMODE_XR) which is set

at task creation. It can be helpful to have human readable identifiers for other OS objects,

as well.

Example

static OS_MAILBOX Mailbox;

static OS_OBJNAME MailboxName;

static char Buffer[100];

OS_MAILBOX_Create(&Mailbox, 10, 10, &Buffer);

OS_DEBUG_SetObjName(&MailboxName, &Mailbox, "My Mailbox");

With the following API you can easily add human readable identifiers to an unlimited amount

of OS objects. Human readable object identifiers are not supported in embOS library mode

OS_LIBMODE_XR.

19.2.1 API functions

Routine Description

main

Task

ISR

Timer

OS_DEBUG_SetObjName() Sets an OS object name. ● ●

OS_DEBUG_GetObjName() Returns the name of an OS object. ● ●

357 CHAPTER 19 Human readable object identiﬁers

19.2.2 OS_DEBUG_SetObjName()

Description

Sets an OS object name.

Prototype

void OS_DEBUG_SetObjName(OS_OBJNAME* pObjName,

OS_CONST_PTR void *pOSObjID,

OS_CONST_PTR char *sName);

Parameters

Parameter Description

pObjName Pointer to a OS_OBJNAME control structure.

pOSObjID ID of the OS object.

sName Name of the OS object.

Additional information

With OS_DEBUG_SetObjName() every OS object like mailbox can have a name. This name

can be shown in debug tools like IDE RTOS plug-ins. Every object name needs a control

structure of type OS_OBJNAME. This function is not available in OS_LIBMODE_XR.

Example

#include "RTOS.h"

#include <stdio.h>

static OS_STACKPTR int StackHP[128];

static OS_TASK TCBHP;

static OS_MAILBOX Mailbox;

static OS_OBJNAME MailboxName;

static char Buffer[100];

static void HPTask(void) {

const char* s;

s = OS_DEBUG_GetObjName(&Mailbox);

printf(s);

while (1) {

OS_TASK_Delay(50);

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize required hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_MAILBOX_Create(&Mailbox, 10, 10, &Buffer);

OS_DEBUG_SetObjName(&MailboxName, &Mailbox, "My Mailbox");

OS_Start(); // Start embOS

return 0;

}

358 CHAPTER 19 Human readable object identiﬁers

19.2.3 OS_DEBUG_GetObjName()

Description

Returns the name of an OS object.

Prototype

char *OS_DEBUG_GetObjName(OS_CONST_PTR void *pOSObjID);

Parameters

Parameter Description

pOSObjID Pointer to the OS object.

Return value

= NULL Name was not set for this object.

≠ NULL Pointer to the OS object name.

Additional information

OS_DEBUG_GetObjName() returns the object name which was set before with OS_DEBUG_Se-

tObjName(). This function is not available in OS_LIBMODE_XR.

Example

For an example, see OS_DEBUG_SetObjName().

Chapter 20

Profiling

360 CHAPTER 20 Introduction

20.1 Introduction

This chapter explains the profiling functions that can be used by an application.

In software engineering, profiling (“program profiling”, “software profiling”) is a form of

dynamic program analysis that measures, for example, the time complexity of a program

and duration of function calls.

Example

#include "RTOS.h"

#include <stdio.h>

static OS_STACKPTR int StackHP[128], StackLP[128], StackSample[128];

static OS_TASK TCBHP, TCBLP, TCBSample;

static void HPTask(void) {

while (1) {

OS_TASK_Delayus(500); // Do something.

OS_TASK_Delay(1); // Give other tasks a chance to run.

}

static void LPTask(void) {

while (1) {

OS_TASK_Delayus(250); // Do something.

OS_TASK_Delay(1); // Give other tasks a chance to run.

}

static void SampleTask(void) {

while (1) {

OS_STAT_Sample(); // Calculate CPU load.

printf("CPU usage of HP Task: %d\n", OS_STAT_GetLoad(&TCBHP));

printf("CPU usage of LP Task: %d\n\n", OS_STAT_GetLoad(&TCBLP));

OS_TASK_Delay(1000); // Wait for at least 1 second before next sampling.

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize the hardware

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_TASK_CREATE(&TCBSample, "Sample Task", 1, SampleTask, StackSample);

OS_Start(); // Start multitasking

return 0;

}

Output

CPU usage of HP Task: 520

CPU usage of LP Task: 268

361 CHAPTER 20 API functions

20.2 API functions

Routine Description

main

Task

ISR

Timer

OS_STAT_AddLoadMeasurement() Initializes the periodic CPU load mea-

surement. ● ●

OS_STAT_AddLoadMeasure-

mentEx() Initializes the periodic CPU load mea-

surement. ● ●

OS_STAT_Disable() Disables the kernel profiling. ● ● ● ●

OS_STAT_Enable() Enables the kernel profiling (for an in-

definite time). ●●●●

OS_STAT_GetExecTime() Returns the total task execution time. ● ● ● ●

OS_STAT_GetLoadMeasurement() Retrieves the result of the CPU load

measurement. ●●●●

OS_STAT_GetLoad() Calculates the current task’s CPU load in

permille. ●●●●

OS_STAT_Sample() Starts the kernel profiling and calculates

the absolute task run time since the last

call to OS_STAT_Sample().

●●●●

362 CHAPTER 20 API functions

20.2.1 OS_STAT_AddLoadMeasurement()

Description

Initializes the periodic CPU load measurement. May be used to start the calculation of the

total CPU load of an application.

Note

OS_STAT_AddLoadMeasurement() starts a CPU load task with a predefined task stack

size of 48 integers. The stack size is sufficient for most applications. However, in

some situations more task stack may be required. In that case please use OS_S-

TAT_AddLoadMeasurementEx() which allows to use an application defined stack size.

Prototype

void OS_STAT_AddLoadMeasurement(int Period,

OS_U8 AutoAdjust,

OS_I32 DefaultMaxValue);

Parameters

Parameter Description

Period Measurement period in embOS system ticks.

AutoAdjust If not zero, the measurement is autoadjusted once initially.

DefaultMaxValue May be used to set a default counter value when AutoAdjust

is not used. (See additional information)

The CPU load is the percentage of CPU time that was not spent in OS_Idle(). To measure

it, OS_STAT_AddLoadMeasurement() creates a task running at highest priority. This task

periodically suspends itself by calling OS_TASK_Delay(Period). Each time it is resumed, it

calculates the CPU load through comparison of two counter values.

For this calculation, it is required that OS_Idle() gets executed and increments a counter

by calling OS_INC_IDLE_CNT(). Furthermore, the calculation will fail if OS_Idle() starts a

power save mode of the CPU. OS_Idle() must therefore be similar to:

void OS_Idle(void) {

while (1) {

OS_INC_IDLE_CNT();

}

The maximum value of the idle counter is stored once at the beginning and is subsequently

used for comparison with the current value of the counter each time the measurement task

gets activated. For this comparison, it is assumed that the maximum value of the counter

represents a CPU load of 0%, whereas a value of zero represents a CPU load of 100%. The

maximum value of the counter can either be examined automatically, or may else be set

manually. When AutoAdjust is non-zero, the task will examine the maximum value of the

counter automatically. To do so, it will initially suspend all other tasks for the Period-time

and will subsequently call OS_TASK_Delay(Period). This way, the entire period is spent in

OS_Idle() and the counter incremented in OS_Idle() reaches its maximum value, which

is then saved and used for comparisons. Especially when the initial suspension of all tasks

for the Period-time is not desired, the maximum counter value may also be configured

manually via the parameter DefaultMaxValue when AutoAdjust is zero.

363 CHAPTER 20 API functions

20.2.1.1 OS_IdleCnt

Description

This global variable holds the counter value used for CPU load measurement. It may be

helpful when examining the appropiate DefaultMaxValue for the manual configuration of

OS_STAT_AddLoadMeasurement().

Declaration

volatile OS_I32 OS_IdleCnt;

Additional information

The appropiate DefaultMaxValue may, for example, be examined prior to creating any

other task, similar to the given sample below:

void MainTask(void) {

OS_I32 DefaultMax;

OS_TASK_Delay(100);

DefaultMax = OS_IdleCnt; /* This value can be used as DefaultMaxValue. */

/* Now other tasks can be created and started. */

}

This function is not available in OS_LIBMODE_SAFE.

364 CHAPTER 20 API functions

20.2.2 OS_STAT_AddLoadMeasurementEx()

Description

Initializes the periodic CPU load measurement. May be used to start the calculation of the

total CPU load of an application.

OS_STAT_AddLoadMeasurementEx() allows to define the stack location and size for the CPU

load task which is started automatically by OS_STAT_AddLoadMeasurementEx()

Prototype

void OS_STAT_AddLoadMeasurementEx(int Period,

OS_U8 AutoAdjust,

OS_I32 DefaultMaxValue,

void OS_STACKPTR *pStack,

OS_UINT StackSize);

Parameters

Parameter Description

Period Measurement period in embOS system ticks.

AutoAdjust If not zero, the measurement is autoadjusted once initially.

DefaultMaxValue May be used to set a default counter value when AutoAdjust

is not used. (See additional information)

pStack Pointer to the stack.

StackSize Size of the stack.

Additional information

Please refer to the description of OS_STAT_AddLoadMeasurement() for more details.

This function is not available in OS_LIBMODE_SAFE.

365 CHAPTER 20 API functions

20.2.3 OS_STAT_Disable()

Description

Disables the kernel profiling.

Prototype

void OS_STAT_Disable(void);

Additional information

The function OS_STAT_Enable() may be used to start profiling.

366 CHAPTER 20 API functions

20.2.4 OS_STAT_Enable()

Description

Enables the kernel profiling (for an indefinite time).

Prototype

void OS_STAT_Enable(void);

Additional information

The function OS_STAT_Disable() may be used to stop profiling.

367 CHAPTER 20 API functions

20.2.5 OS_STAT_GetExecTime()

Description

Returns the total task execution time.

Prototype

OS_U32 OS_STAT_GetExecTime(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask Pointer to a task control block.

Return value

The total task execution time in timer cycles.

Additional information

This function only returns valid values when profiling was enabled before by a call to OS_S-

TAT_Enable(). If pTask is a NULL pointer, the function returns the total task execution

time of the currently running task. If pTask does not specify a valid task, a debug build

of embOS calls OS_Error().

Example

OS_U32 ExecTime;

void MyTask(void) {

OS_STAT_Enable();

while (1) {

ExecTime = OS_STAT_GetExecTime(NULL);

OS_TASK_Delay(100);

}

368 CHAPTER 20 API functions

20.2.6 OS_STAT_GetLoadMeasurement()

Description

Retrieves the result of the CPU load measurement.

Prototype

int OS_STAT_GetLoadMeasurement(void);

Return value

The total CPU load in percent.

Additional information

OS_STAT_GetLoadMeasurement() delivers correct results if

• the CPU load measurement was started before by calling

OS_STAT_AddLoadMeasurement() with auto-adjustment or else with a correct default

value, and

•OS_Idle() updates the measurement by calling OS_INC_IDLE_CNT().

20.2.6.1 OS_CPU_Load

Description

The global variable OS_CPU_Load holds the total CPU load as a percentage. It may prove

helpful to monitor the variable in a debugger with live-watch capability during development.

Declaration

volatile OS_INT OS_CPU_Load;

Additional information

This variable will not contain correct results unless the CPU load measurement was started

by a call to OS_STAT_AddLoadMeasurement(). This function is not available in OS_LIBMOD-

E_SAFE.

369 CHAPTER 20 API functions

20.2.7 OS_STAT_GetLoad()

Description

Calculates the current task’s CPU load in permille.

Prototype

int OS_STAT_GetLoad(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask Pointer to a task control block.

Return value

The current task’s CPU load in permille.

Additional information

OS_STAT_GetLoad() requires OS_STAT_Sample() to be periodically called by the task for

which to measure the CPU load.

OS_STAT_GetLoad() cannot be used from multiple tasks simultaneously for it uses a global

variable.

370 CHAPTER 20 API functions

20.2.8 OS_STAT_Sample()

Description

Starts the kernel profiling and calculates the absolute task run time since the last call to

OS_STAT_Sample().

Prototype

void OS_STAT_Sample(void);

Additional information

OS_STAT_Sample() enables profiling for five consecutive seconds. The next call to OS_S-

TAT_Sample() must be performed within these five seconds. To retrieve the calculated CPU

load in permille, use the embOS function OS_STAT_GetLoad(). OS_STAT_Sample() cannot

be used from multiple tasks simultaneously because it uses a global variable.

Chapter 21

embOSView

372 CHAPTER 21 Overview

21.1 Overview

The embOSView utility is a helpful tool for the analysis of the running target application. It

is shipped as embOSView.exe with embOS and runs on Windows.

Most often, a serial interface (UART) is used for the communication with the target hard-

ware. Alternative communication channels include Ethernet, memory read/write for Cor-

tex-M and RX CPUs, and DCC for ARM7/9 and Cortex-A CPUs. The hardware dependent

routines and defines available for communication with embOSView are implemented inside

the source file RTOSInit.c. Details on how to modify this file are also included in How to

change settings on page 461.

The communication API is not available in embOS library mode OS_LIBMODE_SAFE.

373 CHAPTER 21 Task list window

21.2 Task list window

embOSView shows the state of every task created by the target application in the Task list

window. The information shown depends on the library used in your application.

Item Description Builds

Prio Current priority of task. All

Id Task ID, which is the address of the task con-

trol block. All

Name Name assigned during creation. All

Status Current state of task (ready, executing, delay,

reason for suspension). All

Data Depends on status. All

Timeout Time of next activation. All

Stack Used stack size/max. stack size/stack location. S, SP, D, DP, DT

CPULoad Percentage CPU load caused by task. SP, DP, DT

Run Count Number of activations since reset. SP, DP, DT

Time slice Round-robin time slice All

The Task list window is helpful in analysis of stack usage and CPU load for every running

task.

374 CHAPTER 21 System variables window

21.3 System variables window

embOSView shows the state of major system variables in the System variables window.

The information shown also depends on the library used by your application:

Item Description Builds

OS_VERSION Current version of embOS. All

CPU Target CPU and compiler. All

LibMode Library mode used for target application. All

OS_Time Current system time in system ticks. All

OS_NumTasks Current number of defined tasks. All

OS_Status Current error code (or O.K.). All

OS_pActiveTask Active task that should be running. SP, D, DP, DT

OS_pCurrentTask Actual currently running task. SP, D, DP, DT

SysStack Used size/max. size/location of system

stack. SP, DP, DT

IntStack Used size/max. size/location of interrupt

stack. SP, DP, DT

TraceBuffer Current count/maximum size and current

state of trace buffer. All trace builds

375 CHAPTER 21 Sharing the SIO for terminal I/O

21.4 Sharing the SIO for terminal I/O

The serial input/output (SIO) used by embOSView may also be used by the application at

the same time for both input and output. Terminal input is often used as keyboard input,

where terminal output may be used for outputting debug messages. Input and output is

done via the Terminal window, which can be shown by selecting View/Terminal from

the menu.

To ensure communication via the Terminal window in parallel with the viewer functions,

the application uses the function OS_COM_SendString() for sending a string to the Termi-

nal window and the function OS_COM_SetRxCallback() to hook a reception-routine that

receives one byte.

21.4.1 API functions

Routine Description

main

Task

ISR

Timer

OS_COM_SendString() Sends a string to the embOSView terminal

window. ● ●

OS_COM_SetRxCallback() Sets a callback hook to a routine for receiving

one character from embOSView. ● ● ●

376 CHAPTER 21 Sharing the SIO for terminal I/O

21.4.1.1 OS_COM_SendString()

Description

Sends a string to the embOSView terminal window.

Prototype

void OS_COM_SendString(const char* s);

Parameters

Parameter Description

sPointer to a null-terminated string that should be sent to the

terminal window.

Additional information

This function utilizes the target-specific function OS_COM_Send1() (see OS_COM_Send1()).

377 CHAPTER 21 Sharing the SIO for terminal I/O

21.4.1.2 OS_COM_SetRxCallback()

Description

Sets a callback hook to a routine for receiving one character from embOSView.

Prototype

OS_RX_CALLBACK *OS_COM_SetRxCallback(OS_RX_CALLBACK* cb);

Parameters

Parameter Description

cb Pointer to the application routine that should be called when

one character is received over the serial interface.

Return value

This is the pointer to the callback function that was hooked before the call.

Additional information

The user function is called from embOS. The received character is passed as parameter.

See the example below.

The callback function is defined as:

typedef void OS_RX_CALLBACK (OS_U8 Data);

Example

void GUI_X_OnRx(OS_U8 Data); /* Callback ... called from Rx-interrupt */

void GUI_X_Init(void) {

OS_COM_SetRxCallback(&GUI_X_OnRx);

}

378 CHAPTER 21 Enable communication to embOSView

21.5 Enable communication to embOSView

The communication to embOSView can be enabled by setting the compile time switch

OS_VIEW_IFSELECT to an interface define which may be defined in the project settings or in

the configuration file OS_Config.h. If OS_VIEW_IFSELECT is defined as OS_VIEW_DISABLED,

the communication is disabled. In the RTOSInit files the OS_VIEW_IFSELECT switch is set

to a specific interface if not defined as project option.

The OS_Config.h file sets the compile time switch OS_VIEW_IFSELECT to

OS_VIEW_DISABLED when DEBUG=1 is not defined. Therefore, in the embOS start projects,

the communication is enabled per default when using the Debug configuration, and is dis-

abled when using the Release configuration.

OS_VIEW_IFSELECT Communication interface

OS_VIEW_DISABLED Disabled

OS_VIEW_IF_UART UART

OS_VIEW_IF_JLINK J-Link

OS_VIEW_IF_ETHERNET Ethernet

379 CHAPTER 21 Select the communication channel

21.6 Select the communication channel

When the communication to embOSView is enabled by setting the compile time switch

OS_VIEW_IFSELECT, the communication can be handled via UART, J-Link or ethernet.

21.6.1 Select a UART for communication

Set the compile time switch OS_VIEW_IFSELECT to OS_VIEW_IF_UART by project option/com-

piler preprocessor or in RTOSInit.c to enable the communication via UART.

21.6.2 Select J-Link for communication

Per default, J-Link is selected as communication device in most embOS start projects, if

available.

The compile time switch OS_VIEW_IFSELECT is predefined to OS_VIEW_IF_JLINK in the CPU

specific RTOSInit.c files, thus J-Link communication is selected per default unless over-

written by project / compiler preprocessor options.

21.6.3 Select Ethernet for communication

Set the compile time switch OS_VIEW_IFSELECT to OS_VIEW_IF_ETHERNET by project / com-

piler preprocessor options or in RTOSInit.c to switch the communication to Ethernet.

This communication mode is only available when embOS/IP or a different TCP/IP stack is

included with the project. Also, the file UDP_Process.c must be added to your project and

the file UDPCOM.h to your Start\Inc folder. These files are not shipped with embOS, but

are available on request.

Using a different TCP/IP stack than embOS/IP requires modifications to UDP_Process.c.

380 CHAPTER 21 Setup embOSView for communication

21.7 Setup embOSView for communication

When the communication to embOSView is enabled in the target application, embOSView

can be used to analyze the running application. The communication channel of embOSView

has to be setup according to the communication channel which was selected in the project.

21.7.1 Select a UART for communication

Start embOSView and chose menu Setup:

In the Communication tab, choose UART in the Type selection listbox.

In the Host interface box, select the baud rate for communication and the COM port of the

PC which should be connected to the target board. The default baud rate of all projects is

38,400. The COM port list box lists all currently available COM ports of the PC.

The serial communication will work when the target is running stand-alone or during a

debug session, when the target is connected to a debugger.

The serial connection can be used when the target board has a spare UART port and the

UART functions are included in the application.

381 CHAPTER 21 Setup embOSView for communication

21.7.2 Select J-Link for communication

embOS supports communication channel to embOSView which uses J-Link to communicate

with the running application. embOSView version 3.82g or higher and a J-Link DLL is re-

quired to use J-Link for communication.

To select this communication channel, start embOSView and open the Setup menu:

In the Communication tab, choose J-Link Cortex-M (memory access), J-Link RX (memory

access) or J-Link ARM7/9/11 (DCC) in the Type selection listbox.

In the Host interface box, select the USB or TCP/IP channel used to communicate with

your J-Link.

In the Target interface box, select the communication speed of the target interface and the

physical target connection, which may be a JTAG, SWD or FINE connection.

In the Log File box, choose whether a log file should be created and define its file name

and location.

The JTAG Chain box allows the selection of a specific device in a JTAG scan chain with

multiple devices. Currently, up to eight devices in the scan chain are supported. Two values

must be configured: the position of the target device in the scan chain and the total number

of bits in the instruction registers of the devices before the target device (IR len). Target

position is numbered in descending order, which means the target that is closest to J-Link’s

TDI is in the highest position (max. 7), while the target closest to J-Link’s TDO is in the

lowest position (which is always 0). Upon selecting the position, the according IR len is

determined automatically, which should succeed for most target devices. IR len can also

be written manually, which is mandatory in case automatic detection was not successful.

For further information, please refer to the J-Link / J-Trace User Guide (UM08001, Chapter

5.3 “JTAG interface”).

382 CHAPTER 21 Setup embOSView for communication

21.7.3 Select Ethernet for communication

embOS supports communication channel to embOSView which uses Ethernet to communi-

cate with the running application. embOS/IP, or a different TCP/IP stack, is required to use

Ethernet for communication.

To select this communication channel, start embOSView and open the Setup menu:

In the Communication tab, choose Ethernet in the Type selection listbox.

In the Host interface box, select the IP address of your target and the port number 50021.

383 CHAPTER 21 Setup embOSView for communication

21.7.4 Use J-Link for communication and debugging in paral-

lel

J-Link can be used to communicate with embOSView during a running debug session that

uses the same J-Link as debug probe. To avoid potential incompatibilites, the target inter-

face settings for J-Link should be the same in the debugger settings and in the embOSView

Target interface settings.

To use embOSView during a debug session, proceed as follows:

• Examine the target interface settings in the Debugger settings of the project.

• Before starting the debugger, start embOSView and set the same target interface as

found in the debugger settings.

• Close embOSView.

• Start the debugger.

• Restart embOSView.

J-Link will now communicate with the debugger and embOSView will simultaneously com-

municate with embOS via J-Link.

21.7.5 Restrictions for using J-Link with embOSView

With the current version of embOSView, J-Link communication with Cortex-M (memory

access) can only be used when the Cortex-M vector table of the target application is located

at address 0x0.

384 CHAPTER 21 Using the API trace

21.8 Using the API trace

embOS contains a trace feature for API calls. This requires the use of the trace build libraries

in the target application.

The trace build libraries implement a buffer for 100 trace entries. Tracing of API calls can be

started and stopped from embOSView via the Trace menu, or from within the application

by using the functions OS_TRACE_Enable() and OS_TRACE_Disable(). Individual filters may

be defined to determine which API calls should be traced for different tasks or from within

interrupt or timer routines. Once the trace is started, the API calls are recorded in the trace

buffer, which is periodically read by embOSView. The result is shown in the Trace window:

Every entry in the Trace list is recorded with the actual system time. In case of calls

or events from tasks, the task ID (TaskId) and task name (TaskName) (limited to 15

characters) are also recorded. Parameters of API calls are recorded if possible, and are

shown as part of the APIName column. In the example above, this can be seen with

OS_TASK_Delay(10). Once the trace buffer is full, trace is automatically stopped. The Trace

list and buffer can be cleared from embOSView.

21.8.1 Settings up trace from embOSView

Three different kinds of trace filters are defined for tracing. These filters can be set up from

embOSView via the menu Options/Setup/Trace.

Filter 0 is not task-specific and records all specified events regardless of the task. As the

Idle loop is not a task, calls from within the idle loop are not traced.

Filter 1 is specific for interrupt service routines, software timers and all calls that occur

outside a running task. These calls may come from the idle loop or during startup when

no task is running.

Filters 2 to 4 allow trace of API calls from named tasks.

385 CHAPTER 21 Using the API trace

To enable or disable a filter, simply check or uncheck the corresponding checkboxes labeled

Filter 4 Enable to Filter 0 Enable. For any of these five filters, individual API functions can

be enabled or disabled by checking or unchecking the corresponding checkboxes in the list.

To speed up the process, there are two buttons available:

•Select all - enables trace of all API functions for the currently enabled (checked) filters.

•Deselect all - disables trace of all API functions for the currently enabled (checked)

filters.

Filter 2, Filter 3, and Filter 4 allow tracing of task-specific API calls. A task name can

therefore be specified for each of these filters. In the example above, Filter 4 is configured

to trace calls of OS_TASK_Delay() from the task called MainTask. After the settings are

saved (via the Apply or OK button), the new settings are sent to the target application.

386 CHAPTER 21 Trace ﬁlter setup functions

21.9 Trace filter setup functions

Tracing of API or user function calls can be started or stopped from embOSView. By default,

trace is initially disabled in an application program. It may be helpful to control recording

of trace events directly from the application, using the following functions.

21.9.1 API functions

Routine Description

main

Task

ISR

Timer

OS_TRACE_Enable() Enables tracing of filtered API calls. ● ● ● ●

OS_TRACE_EnableAll() Sets up Filter 0 (any task), enables trac-

ing of all API calls and then enables the

trace function.

●●●●

OS_TRACE_EnableId()

Sets the specified ID value in Filter 0

(any task), thus enabling trace of the

specified function, but does not start

trace.

●●●●

OS_TRACE_EnableFilterId()

Sets the specified ID value in the spec-

ified trace filter, thus enabling trace of

the specified function, but does not start

trace.

●●●●

OS_TRACE_Disable() Disables tracing of filtered API and user

function calls. ●●●●

OS_TRACE_DisableAll() Sets up Filter 0 (any task), disables

tracing of all API calls and also disables

trace.

●●●●

OS_TRACE_DisableId()

Resets the specified ID value in Filter 0

(any task), thus disabling trace of the

specified function, but does not stop

trace.

●●●●

OS_TRACE_DisableFilterId()

Resets the specified ID value in the spec-

ified trace filter, thus disabling trace of

the specified function, but does not stop

trace.

●●●●

387 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.1 OS_TRACE_Enable()

Description

Enables tracing of filtered API calls.

Prototype

void OS_TRACE_Enable(void);

Additional information

The trace filter conditions must be set up before calling this function. This functionality

is available in trace builds only. In non-trace builds, the API call is removed by the pre-

processor.

388 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.2 OS_TRACE_EnableAll()

Description

Sets up Filter 0 (any task), enables tracing of all API calls and then enables the trace

function.

Prototype

void OS_TRACE_EnableAll(void);

Additional information

The trace filter conditions of all the other trace filters are not affected. This functionality

is available in trace builds only. In non-trace builds, the API call is removed by the pre-

processor.

389 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.3 OS_TRACE_EnableId()

Description

Sets the specified ID value in Filter 0 (any task), thus enabling trace of the specified func-

tion, but does not start trace.

Prototype

void OS_TRACE_EnableId(OS_U8 id);

Parameters

Parameter Description

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

Additional information

To enable trace of a specific embOS API function, you must use the correct Id value. These

values are defined as symbolic constants in RTOS.h. This function may also enable trace of

your own functions. This functionality is available in trace builds only. In non-trace builds,

the API call is removed by the preprocessor.

390 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.4 OS_TRACE_EnableFilterId()

Description

Sets the specified ID value in the specified trace filter, thus enabling trace of the specified

function, but does not start trace.

Prototype

void OS_TRACE_EnableFilterId(OS_U8 FilterIndex,

OS_U8 id);

Parameters

Parameter Description

FilterIndex Index of the filter that should be affected:

0 ≤ FilterIndex ≤ 4

0 affects Filter 0 (any task) and so on.

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 are reserved for embOS.

Additional information

To enable trace of a specific embOS API function, you must use the correct Id value. These

values are defined as symbolic constants in RTOS.h. This function may also be used for

enabling trace of your own functions. This functionality is available in trace builds only. In

non-trace builds, the API call is removed by the preprocessor.

391 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.5 OS_TRACE_Disable()

Description

Disables tracing of filtered API and user function calls.

Prototype

void OS_TRACE_Disable(void);

Additional information

This functionality is available in trace builds only. In non-trace builds, the API call is removed

by the preprocessor.

392 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.6 OS_TRACE_DisableAll()

Description

Sets up Filter 0 (any task), disables tracing of all API calls and also disables trace.

Prototype

void OS_TRACE_DisableAll(void);

Additional information

The trace filter conditions of all the other trace filters are not affected, but tracing is stopped.

This functionality is available in trace builds only. In non-trace builds, the API call is removed

by the preprocessor.

393 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.7 OS_TRACE_DisableId()

Description

Resets the specified ID value in Filter 0 (any task), thus disabling trace of the specified

function, but does not stop trace.

Prototype

void OS_TRACE_DisableId(OS_U8 id);

Parameters

Parameter Description

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

Additional information

To disable trace of a specific embOS API function, you must use the correct Id value. These

values are defined as symbolic constants in RTOS.h. This function may also be used for

disabling trace of your own functions. This functionality is available in trace builds only. In

non-trace builds, the API call is removed by the preprocessor.

394 CHAPTER 21 Trace ﬁlter setup functions

21.9.1.8 OS_TRACE_DisableFilterId()

Description

Resets the specified ID value in the specified trace filter, thus disabling trace of the specified

function, but does not stop trace.

Prototype

void OS_TRACE_DisableFilterId(OS_U8 FilterIndex,

OS_U8 id);

Parameters

Parameter Description

FilterIndex Index of the filter that should be affected:

0 ≤ FilterIndex ≤ 4

0 affects Filter 0 (any task) and so on.

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

Additional information

To disable trace of a specific embOS API function, you must use the correct Id value. These

values are defined as symbolic constants in RTOS.h. This function may also be used for

disabling trace of your own functions. This functionality is available in trace builds only. In

non-trace builds, the API call is removed by the preprocessor.

395 CHAPTER 21 Trace record functions

21.10 Trace record functions

The following functions write data into the trace buffer. As long as only embOS API calls

should be recorded, these functions are used internally by the trace build libraries. If, for

some reason, you want to trace your own functions with your own parameters, you may

call one of these routines.

All of these functions have the following points in common:

• To record data, trace must be enabled.

• An ID value in the range 100 to 127 must be used as the ID parameter. ID values from

0 to 99 and 128 to 255 are internally reserved for embOS.

• The events specified as ID must be enabled in trace filters.

• Active system time and the current task are automatically recorded together with the

specified event.

21.10.1 API functions

Routine Description

main

Task

ISR

Timer

OS_TRACE_Data() Writes an entry with ID and an integer as para-

meter into the trace buffer. ●●●●

OS_TRACE_DataPtr() Writes an entry with ID, an integer, and a pointer

as parameter into the trace buffer. ●●●●

OS_TRACE_Ptr() Writes an entry with ID and a pointer as parame-

ter into the trace buffer. ●●●●

OS_TRACE_U32Ptr() Writes an entry with ID, a 32 bit unsigned inte-

ger, and a pointer as parameter into the trace

buffer.

●●●●

OS_TRACE_Void() Writes an entry identified only by its ID into the

trace buffer. ●●●●

396 CHAPTER 21 Trace record functions

21.10.1.1 OS_TRACE_Data()

Description

Writes an entry with ID and an integer as parameter into the trace buffer.

Prototype

void OS_TRACE_Data(OS_U8 id,

int v);

Parameters

Parameter Description

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

vAny integer value that should be recorded as parameter.

Additional information

The value passed as parameter will be displayed in the trace list window of embOSView. This

functionality is available in trace builds only. In non-trace builds, the API call is removed

by the preprocessor.

397 CHAPTER 21 Trace record functions

21.10.1.2 OS_TRACE_DataPtr()

Description

Writes an entry with ID, an integer, and a pointer as parameter into the trace buffer.

Prototype

void OS_TRACE_DataPtr( OS_U8 id,

int v,

volatile OS_CONST_PTR void *p);

Parameters

Parameter Description

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

vAny integer value that should be recorded as parameter.

pAny void pointer that should be recorded as parameter.

Additional information

The values passed as parameters will be displayed in the trace list window of embOSView.

This functionality is available in trace builds only. In non-trace builds, the API call is removed

by the preprocessor.

398 CHAPTER 21 Trace record functions

21.10.1.3 OS_TRACE_Ptr()

Description

Writes an entry with ID and a pointer as parameter into the trace buffer.

Prototype

void OS_TRACE_Ptr( OS_U8 id,

volatile OS_CONST_PTR void *p);

Parameters

Parameter Description

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

pAny void pointer that should be recorded as parameter.

Additional information

The pointer passed as parameter will be displayed in the trace list window of embOSView.

This functionality is available in trace builds only. In non-trace builds, the API call is removed

by the preprocessor.

399 CHAPTER 21 Trace record functions

21.10.1.4 OS_TRACE_U32Ptr()

Description

Writes an entry with ID, a 32 bit unsigned integer, and a pointer as parameter into the

trace buffer.

Prototype

void OS_TRACE_U32Ptr( OS_U8 id,

OS_U32 p0,

volatile OS_CONST_PTR void *p1);

Parameters

Parameter Description

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

p0 Any unsigned 32 bit value that should be recorded as para-

meter.

p1 Any void pointer that should be recorded as parameter.

Additional information

This function may be used for recording two pointers. The values passed as parameters will

be displayed in the trace list window of embOSView. This functionality is available in trace

builds only. In non-trace builds, the API call is removed by the preprocessor.

400 CHAPTER 21 Trace record functions

21.10.1.5 OS_TRACE_Void()

Description

Writes an entry identified only by its ID into the trace buffer.

Prototype

void OS_TRACE_Void(OS_U8 id);

Parameters

Parameter Description

id ID value of API call that should be enabled for trace:

0 ≤ id ≤ 255

Values from 0 to 99 and 128 to 255 are reserved for embOS.

Additional information

This functionality is available in trace builds only, and the API call is not removed by the

preprocessor.

401 CHAPTER 21 Application-controlled trace example

21.11 Application-controlled trace example

As described in the previous section, the user application can enable and set up the trace

conditions without a connection or command from embOSView. The trace record functions

can also be called from any user function to write data into the trace buffer, using ID

numbers from 100 to 127.

Controlling trace from the application can be useful for tracing API and user functions just

after starting the application, when the communication to embOSView is not yet available

or when the embOSView setup is not complete.

The example below shows how a trace filter can be set up by the application. The func-

tion OS_TRACE_EnableID() sets trace filter 0 which affects calls from any running task.

Therefore, the first call to SetState() in the example would not be traced because there

is no task running at that moment. The additional filter setup routine OS_TRACE_Enable-

FilterId() is called with filter 1, which results in tracing calls from outside running tasks.

Example code

#include "RTOS.h"

#define APP_TRACE_ID_SETSTATE 100 // Application specific trace id

char MainState;

void SetState(char* pState, char Value) {

#if (OS_TRACE != 0)

OS_TRACE_DataPtr(APP_TRACE_ID_SETSTATE, Value, pState);

#endif

*pState = Value;

}

int main(void) {

OS_Init();

OS_InitHW();

#if (OS_TRACE != 0)

OS_TRACE_DisableAll(); // Disable all API trace calls

OS_TRACE_EnableId(APP_TRACE_ID_SETSTATE); // User trace

OS_TRACE_EnableFilterId(0, APP_TRACE_ID_SETSTATE); // User trace

OS_TRACE_Enable();

#endif

SetState(&MainState, 1);

OS_TASK_CREATE(&TCBMain, "MainTask", 100, MainTask, MainStack);

OS_Start(); // Start multitasking

return 0;

}

By default, embOSView lists all user function traces in the trace list window as Routine,

followed by the specified ID and two parameters as hexadecimal values. The example above

would result in the following:

Routine100(0xabcd, 0x01)

where 0xabcd is the pointer address and 0x01 is the parameter recorded from

OS_TRACE_DataPtr().

402 CHAPTER 21 User-deﬁned functions

21.12 User-defined functions

To use the built-in trace (available in trace builds of embOS) for application program user

functions, embOSView can be customized. This customization is done in the setup file em-

bOS.ini.

This setup file is parsed at the startup of embOSView. It is optional; you will not see an

error message if it cannot be found.

To enable trace setup for user functions, embOSView needs to know an ID number, the

function name and the type of two optional parameters that can be traced. The format is

explained in the following sample embOS.ini file:

Example code

# File: embOS.ini

# embOSView Setup file

# embOSView loads this file at startup. It must reside in the same

# directory as the executable itself.

# Note: The file is not required to run embOSView. You will not get

# an error message if it is not found. However, you will get an error message

# if the contents of the file are invalid.

# Define add. API functions.

# Syntax: API( <Index>, <Routinename> [parameters])

# Index: Integer, between 100 and 127

# Routinename: Identifier for the routine. Should be no more than 32 characters

# parameters: Optional paramters. A max. of 2 parameters can be specified.

# Valid parameters are:

# int

# ptr

# Every parameter must be placed after a colon.

API( 100, "Routine100")

API( 101, "Routine101", int)

API( 102, "Routine102", int, ptr)

Chapter 22

MPU - Memory Protection

404 CHAPTER 22 Introduction

22.1 Introduction

This chapter describes embOS-MPU. embOS-MPU is a separate product which adds memory

protection to embOS.

Memory protection is a way to control memory access rights, and is a part of most modern

processor architectures and operating systems. The main purpose of memory protection is

to prevent a task from accessing memory that has not been allocated to it. This prevents

a bug or malware within a task from affecting other tasks, or the operating system itself.

embOS-MPU uses the hardware MPU and additional checks to avoid that a task affects the

remaining system. Even if a bug in one task occurs all other tasks and the OS continue

execution. The task which caused the issue is terminated automatically and the application

is informed via an optional callback function.

Since a hardware MPU is required embOS MPU support is unavailable for some embOS

ports. The MPU support is included in separate embOS ports and is not part of the general

embOS port.

22.1.1 Privilege states

Application tasks which may affect other tasks or the OS itself must not have the permission

to access the whole memory, special function registers or embOS control structures. Such

application code could be e.g. unreliable software from a third party vendor.

Therefore, those application tasks do not run on the same privileged state like the OS. The

OS runs in privileged state which means that it has full access to all memory, peripherals

and CPU features. Application tasks, on the other hand, run in unprivileged state and have

restricted access only to the memory. To access peripherals and memory from unprivileged

tasks, additional API and specific device drivers may be used.

State Description

Privileged Full access to memory, peripheral and CPU features

Unprivileged Only restricted access to memory, no direct access to pe-

ripherals, no access to some CPU features

22.1.2 Code organization

embOS-MPU assumes that the application code is divided into two parts. The first part runs

in privileged state: it initializes the MPU settings and includes the device driver. It contains

critical code and must be verified for full reliability by the responsible developers. Usually,

this code consists of only a few simple functions which may be located in one single C file.

The second part is the application itself which doesn’t need to or in some cases can’t be

verified for full reliability. As it runs in unprivileged state, it can’t affect the remaining

system. Usually, this code is organized in several C files. This can e.g. simplify a certification.

Part Description

1st part Task and MPU initialization

Device drivers

2nd part Application code from e.g. third party vendor

405 CHAPTER 22 Memory Access permissions

22.2 Memory Access permissions

All privileged tasks have full access to the whole memory. An unprivileged task, however,

can have access to several memory regions with different access permissions. Access per-

missions for RAM and ROM can be used combined, e.g. a ROM region could be readable

and code execution could be allowed. In that case the permission defines would be used

as OS_MPU_READONLY | OS_MPU_EXECUTION_ALLOWED.

The following memory access permissions exist:

Permission Description

OS_MPU_NOACCESS No access to a memory region

OS_MPU_READONLY Read only access to a memory region

OS_MPU_READWRITE Read and write access to a memory region

Permission Description

OS_MPU_EXECUTION_ALLOWED Code execution is allowed

OS_MPU_EXECUTION_DISALLOWED Code execution is not allowed

22.2.1 Default memory access permissions

A newly created unprivileged task has per default only access to the following memory

regions:

Region Permissions

ROM OS_MPU_READONLY, OS_MPU_EXECUTION_ALLOWED

RAM OS_MPU_READONLY, OS_MPU_EXECUTION_ALLOWED

Task stack OS_MPU_READWRITE, OS_MPU_EXECUTION_ALLOWED

An unprivileged task can read and execute the whole RAM and ROM. Write access is re-

stricted to its own task stack. More access rights can be added by embOS API calls.

22.2.2 Interrupts

Interrupts are always privileged and can access the whole memory.

22.2.3 Access to additional memory regions

An unprivileged task can have access to additional memory regions. This could be necessary

e.g when a task needs to write LCD data to a frame buffer in RAM. Using a device driver

could be too inefficient. Additional memory regions can be added with the API function

OS_MPU_AddRegion(). It is CPU specific if the region has to be aligned. Please refer to the

according CPU/ compiler specific embOS manual for more details.

22.2.4 Access to OS objects

An unprivileged task has no direct write access to embOS objects. It also has per default

no access via embOS API functions. Access to OS objects can be added with OS_MPU_Se-

tAllowedObjects(). The object list must be located in ROM memory. The OS object must

be created in the privileged part of the task.

406 CHAPTER 22 ROM placement of embOS

22.3 ROM placement of embOS

embOS must be placed in one memory section. embOS-MPU needs this information to e.g.

check that supervisor calls are made from embOS API functions only. The address and the

size of this section must be passed to embOS with OS_MPU_ConfigMem(). __os_start__

and __os_size__ are linker symbols which are defined in the linker file.

Example

This example is for the GCC compiler and linker.

Linker file:

__os_load_start__ = ALIGN(__text_end__ , 4);

.os ALIGN(__text_end__ , 4) : AT(ALIGN(__text_end__ , 4))

{

__os_start__ = .;

*(.os .os.*)

}

__os_end__ = __os_start__ + SIZEOF(.os);

__os_size__ = SIZEOF(.os);

__os_load_end__ = __os_end__;

C Code:

void OS_InitHW() {

OS_MPU_ConfigMem(0x08000000u, 0x00100000u, // ROM base address and size

0x20000000u, 0x00020000u, // RAM base address and size

__os_start__, __os_size__); // OS base address and size

}

407 CHAPTER 22 Allowed embOS API in unprivileged tasks

22.4 Allowed embOS API in unprivileged tasks

Not all embOS API functions are allowed to be called from an unprivileged task. Only the

following API is allowed in unprivileged task:

Allowed embOS API

General API

OS_IsRunning()

Task API

OS_TASK_Delay()

OS_TASK_DelayUntil()

OS_TASK_Delayus()

OS_TASK_GetID()

OS_TASK_GetName()

OS_TASK_GetNumTasks()

OS_TASK_GetPriority()

OS_TASK_GetSuspendCnt()

OS_TASK_GetTimeSliceRem()

OS_TASK_IsTask()

OS_TASK_Index2Ptr()

OS_TASK_Resume()

OS_TASK_Suspend()

OS_TASK_Wake()

OS_TASK_Yield()

Software timer API

OS_TIMER_GetPeriod()

OS_TIMER_GetRemainingPeriod()

OS_TIMER_GetStatus()

OS_TIMER_GetCurrent()

OS_TIMER_Restart()

OS_TIMER_SetPeriod()

OS_TIMER_Start()

OS_TIMER_Stop()

OS_TIMER_Trigger()

OS_TIMER_GetPeriodEx()

OS_TIMER_GetRemainingPeriodEx()

OS_TIMER_GetStatusEx()

OS_TIMER_GetCurrentEx()

OS_TIMER_RestartEx()

OS_TIMER_SetPeriodEx()

OS_TIMER_StartEx()

OS_TIMER_StopEx()

OS_TIMER_TriggerEx()

Task events API

OS_TASKEVENT_Clear()

OS_TASKEVENT_ClearEx()

408 CHAPTER 22 Allowed embOS API in unprivileged tasks

Allowed embOS API

OS_TASKEVENT_Get()

OS_TASKEVENT_Set()

OS_TASKEVENT_GetBlocked()

OS_TASKEVENT_GetSingleBlocked()

OS_TASKEVENT_GetTimed()

OS_TASKEVENT_GetSingleTimed()

Event objects API

OS_EVENT_Get()

OS_EVENT_GetBlocked()

OS_EVENT_GetTimed()

OS_EVENT_GetMask()

OS_EVENT_GetMaskBlocked()

OS_EVENT_GetMaskTimed()

OS_EVENT_GetMaskMode()

OS_EVENT_GetResetMode()

OS_EVENT_Pulse()

OS_EVENT_Reset()

OS_EVENT_Set()

OS_EVENT_SetMask()

OS_EVENT_SetMaskMode()

OS_EVENT_SetResetMode()

Mutex API

OS_MUTEX_GetValue()

OS_MUTEX_GetOwner()

OS_MUTEX_Lock()

OS_MUTEX_LockBlocked()

OS_MUTEX_LockTimed()

OS_MUTEX_Unlock()

Semaphore API

OS_SEMAPHORE_GetValue()

OS_SEMAPHORE_Give()

OS_SEMAPHORE_GiveMax()

OS_SEMAPHORE_SetValue()

OS_SEMAPHORE_Take()

OS_SEMAPHORE_TakeBlocked()

OS_SEMAPHORE_TakeTimed()

Mailbox API

OS_MAILBOX_Clear()

OS_MAILBOX_Get()

OS_MAILBOX_Get1()

OS_MAILBOX_GetBlocked()

OS_MAILBOX_GetBlocked1()

OS_MAILBOX_GetMessageCnt()

409 CHAPTER 22 Allowed embOS API in unprivileged tasks

Allowed embOS API

OS_MAILBOX_GetTimed()

OS_MAILBOX_GetTimed1()

OS_MAILBOX_GetPtr()

OS_MAILBOX_GetPtrBlocked()

OS_MAILBOX_Peek()

OS_MAILBOX_Purge()

OS_MAILBOX_Put()

OS_MAILBOX_Put1()

OS_MAILBOX_PutBlocked()

OS_MAILBOX_PutBlocked1()

OS_MAILBOX_PutFront()

OS_MAILBOX_PutFront1()

OS_MAILBOX_PutFrontBlocked()

OS_MAILBOX_PutFrontBlocked1()

OS_MAILBOX_PutTimed()

OS_MAILBOX_PutTimed1()

OS_MAILBOX_WaitBlocked()

OS_MAILBOX_WaitTimed()

Queue API

OS_QUEUE_Clear()

OS_QUEUE_IsInUse()

OS_QUEUE_GetMessageCnt()

OS_QUEUE_GetMessageSize()

OS_QUEUE_GetPtr()

OS_QUEUE_GetPtrBlocked()

OS_QUEUE_GetPtrTimed()

OS_QUEUE_PeekPtr()

OS_QUEUE_Purge()

OS_QUEUE_Put()

OS_QUEUE_PutEx()

OS_QUEUE_PutBlocked()

OS_QUEUE_PutBlockedEx()

OS_QUEUE_PutTimed()

OS_QUEUE_PutTimedEx()

Watchdog

OS_WD_Trigger()

Interrupt API

OS_INT_InInterrupt()

Timing API

OS_TIME_GetTicks()

OS_TIME_GetTicks32()

OS_TIME_StartMeasurement()

OS_TIME_StopMeasurement()

410 CHAPTER 22 Allowed embOS API in unprivileged tasks

Allowed embOS API

OS_TIME_GetResult()

OS_TIME_GetResultus()

OS_TIME_Getus()

OS_TIME_Getus64()

OS_ConvertCycles2us()

Low power API

OS_POWER_GetMask()

OS_POWER_UsageInc()

OS_POWER_UsageDec()

Fixed block size memory pool API

OS_MEMPOOL_Alloc()

OS_MEMPOOL_AllocBlocked()

OS_MEMPOOL_AllocTimed()

OS_MEMPOOL_IsInPool()

OS_MEMPOOL_FreeEx()

OS_MEMPOOL_Free()

OS_MEMPOOL_GetBlockSize()

OS_MEMPOOL_GetMaxUsed()

OS_MEMPOOL_GetNumBlocks()

OS_MEMPOOL_GetNumFreeBlocks()

Debug API

OS_DEBUG_GetObjName()

OS_COM_SendString()

Info routines API

OS_INFO_GetCPU()

OS_INFO_GetLibMode()

OS_INFO_GetLibName()

OS_INFO_GetModel()

OS_INFO_GetVersion()

Stack info API

OS_STACK_GetTaskStackBase()

OS_STACK_GetTaskStackSize()

OS_STACK_GetTaskStackSpace()

OS_STACK_GetTaskStackUsed()

OS_STACK_GetSysStackBase()

OS_STACK_GetSysStackSize()

OS_STACK_GetSysStackSpace()

OS_STACK_GetSysStackUsed()

OS_STACK_GetIntStackBase()

OS_STACK_GetIntStackSize()

OS_STACK_GetIntStackSpace()

OS_STACK_GetIntStackUsed()

OS_STACK_GetCheckLimit()

411 CHAPTER 22 Allowed embOS API in unprivileged tasks

Allowed embOS API

MPU API

OS_MPU_CallDeviceDriver()

OS_MPU_GetThreadState()

OS_MPU_SanityCheck()

412 CHAPTER 22 Device driver

22.5 Device driver

22.5.1 Concept

An unprivileged task has no access to any peripheral. Thus a device driver is necessary to

use peripherals like UART, SPI or port pins.

A device driver consists of two parts, an unprivileged part and a privileged part. embOS

ensures there is only one explicit and safe way to switch from the unprivileged part to the

privileged part. The application must call driver functions only in the unprivileged part. The

actual peripheral access is performed in the privileged part only.

OS_MPU_CallDeviceDriver() is used to call the device driver. The first parameter is the

index of the device driver function. Optional parameters can be passed to the device driver.

Note

You must not call any embOS API from a device driver.

Example

A device driver for a LED should be developed. The LED driver can toggle a LED with a

given index number. The function BSP_Toggle_LED() is the unprivileged part of the driver.

It can be called by the unprivileged application.

typedef struct BSP_LED_PARAM_STRUCT {

BSP_LED_DRIVER_API Action;

OS_U32 Index;

} BSP_LED_PARAM;

void BSP_ToggleLED(int Index) {

BSP_LED_PARAM p;

p.Action = BSP_LED_TOGGLE;

p.Index = Index;

OS_MPU_CallDeviceDriver(0u, &p);

}

The device driver itself runs in privileged state and accesses the LED port pin.

void BSP_LED_DeviceDriver(void* Param) {

BSP_LED_PARAM* p;

p = (BSP_LED_PARAM*)Param;

switch (p->Action) {

case BSP_LED_SET:

BSP_SetLED_SVC(p->Index);

break;

case BSP_LED_CLR:

BSP_ClrLED_SVC(p->Index);

break;

case BSP_LED_TOGGLE:

BSP_ToggleLED_SVC(p->Index);

break;

default:

break;

}

413 CHAPTER 22 Device driver

All device driver addresses are stored in one const list which is passed to embOS-MPU with

OS_MPU_SetDeviceDriverList().

static const OS_MPU_DEVICE_DRIVER_FUNC _DeviceDriverList[] =

{ BSP_LED_DeviceDriver,

NULL }; // Last item must be NULL

void BSP_Init(void) {

OS_MPU_SetDeviceDriverList(_DeviceDriverList);

}

414 CHAPTER 22 API functions

22.6 API functions

Routine Description

main

Priv Task

Unpriv Task

ISR

TIMER

OS_MPU_AddRegion() Adds an additional memory region

to which the task has access. ● ●

OS_MPU_CallDeviceDriver() Calls a device driver. ● ● ● ●

OS_MPU_ConfigMem() Configures basic memory informa-

tion. ● ● ● ●

OS_MPU_Enable() Initializes the MPU hardware with

the default MPU API list and en-

ables it.

● ●

OS_MPU_EnableEx() Initializes the MPU hardware with

the specified MPU API list and en-

ables it.

● ●

OS_MPU_ExtendTaskContext() Extends the task context for the

MPU registers. ●

OS_MPU_GetThreadState() Returns the current privileged

task state. ●●●●●

OS_MPU_SetAllowedObjects() Sets a task specific list of objects

to which the task has access via

embOS API functions.

● ● ● ●

OS_MPU_SetDeviceDriverList() Sets the device driver list. ● ● ● ●

OS_MPU_SetErrorCallback() Sets the MPU error callback func-

tion. ● ● ● ●

OS_MPU_SwitchToUnprivState() Switches a task to unprivileged

state. ●

OS_MPU_SwitchToUnprivStateEx()

Switches a task to unprivileged

state and calls a task function

which runs on a separate task

stack.

●

OS_MPU_SetSanityCheckBuffer()

Sets the pointer in the task con-

trol block to a buffer which holds a

copy of the MPU register for sanity

check.

● ● ● ●

OS_MPU_SanityCheck() Performs an MPU sanity check

which checks if the MPU register

still have the correct value.

●

415 CHAPTER 22 API functions

22.6.1 OS_MPU_AddRegion()

Description

Adds an additional memory region to which the task has access.

Prototype

void OS_MPU_AddRegion(OS_TASK* pTask,

OS_U32 BaseAddr,

OS_U32 Size,

OS_U32 Permissions,

OS_U32 Attributes);

Parameters

Parameter Description

pTask Pointer to a task control block.

BaseAddr Region base address.

Size Region size.

Permissions Access permissions.

Attributes Additional core specific memory attributes.

Additional information

This function can be used if a task needs access to additional RAM regions. This RAM region

can be e.g. a LCD frame buffer or a queue data buffer. It is CPU specific if the region has

to be aligned. Please refer to the according CPU/compiler specific embOS manual for more

details.

A memory region can have the following access permissions:

Permission Description

OS_MPU_NOACCESS No access to memory region

OS_MPU_READONLY Read only access to memory region

OS_MPU_READWRITE Read and write access to memory region

OS_MPU_EXECUTION_ALLOWED Code execution is allowed

OS_MPU_EXECUTION_DISALLOWED Code execution is not allowed

Access permissions for data and code execution can be jointly set for one region. A region

can for example be set to read only and code execution can be disabled (OS_MPU_READONLY

| OS_MPU_EXECUTION_DISALLOWED). Per default an unprivileged task has only access to the

following memory regions:

Region Permission

ROM Read and execution access for complete ROM

RAM Read only and and execution access for complete

RAM

Task stack Read and write and execution access to the task

stack

Example

static void HPTask(void) {

OS_MPU_AddRegion(&TCBHP, (OS_U32)MyQBuffer, 512, OS_MPU_READWRITE, 0u);

}

416 CHAPTER 22 API functions

22.6.2 OS_MPU_CallDeviceDriver()

Description

Calls a device driver.

Prototype

void OS_MPU_CallDeviceDriver(OS_U32 Index,

void* Param);

Parameters

Parameter Description

Index Index of device driver function.

Param Parameter to device driver.

Additional information

Unprivileged tasks have no direct access to any peripherals. A device driver is instead

necessary. OS_MPU_CallDeviceDriver() is used to let embOS call the device driver which

then runs in privileged state. Optional parameter can be passed to the driver function. The

device driver is called e.g. for Cortex-M via SVC call.

Example

typedef struct BSP_LED_PARAM_STRUCT {

BSP_LED_DRIVER_API Action;

OS_U32 Index;

} BSP_LED_PARAM;

static const OS_MPU_DEVICE_DRIVER_FUNC _DeviceDriverList[] =

{ BSP_LED_DeviceDriver,

NULL }; // Last item must be NULL

void BSP_LED_DeviceDriver(void* Param) {

BSP_LED_PARAM* p;

p = (BSP_LED_PARAM*)Param;

switch (p->Action) {

case BSP_LED_SET:

BSP_SetLED_SVC(p->Index);

break;

case BSP_LED_CLR:

BSP_ClrLED_SVC(p->Index);

break;

case BSP_LED_TOGGLE:

BSP_ToggleLED_SVC(p->Index);

break;

default:

break;

}

void BSP_ToggleLED(int Index) {

BSP_LED_PARAM p;

p.Action = BSP_LED_TOGGLE;

p.Index = Index;

OS_MPU_CallDeviceDriver(0u, &p);

}

417 CHAPTER 22 API functions

22.6.3 OS_MPU_ConfigMem()

Description

Configures basic memory information. OS_MPU_ConfigMem() tells embOS where ROM, RAM

and the embOS code is located in memory. This information is used to setup the default

task regions at task creation.

Prototype

void OS_MPU_ConfigMem(OS_U32 ROM_BaseAddr,

OS_U32 ROM_Size,

OS_U32 RAM_BaseAddr,

OS_U32 RAM_Size,

OS_U32 OS_BaseAddr,

OS_U32 OS_Size);

Parameters

Parameter Description

ROM_BaseAddr ROM base addr.

ROM_Size ROM size.

RAM_BaseAddr RAM base addr.

RAM_Size RAM size.

OS_BaseAddr embOS ROM region base address.

OS_Size embOS ROM region size.

Additional information

This function must be called before any unprivileged task is created.

Example

void main(void) {

OS_MPU_ConfigMem(0x08000000u,

0x00100000u,

0x20000000u,

0x00020000u,

__os_start__,

__os_size__);

}

418 CHAPTER 22 API functions

22.6.4 OS_MPU_Enable()

Description

Initializes the MPU hardware with the default MPU API list and enables it.

Prototype

void OS_MPU_Enable(void);

Additional information

This function must be called before any embOS-MPU related function is used or any task

is created.

419 CHAPTER 22 API functions

22.6.5 OS_MPU_EnableEx()

Description

Initializes the MPU hardware with the specified MPU API list and enables it.

Prototype

void OS_MPU_EnableEx(OS_CONST_PTR OS_MPU_API_LIST *pAPIList);

Parameters

Parameter Description

pAPIList Pointer to core specific MPU API list.

Additional information

This function must be called before any embOS-MPU related function is used or any task

is created.

Example

void main(void) {

OS_MPU_EnableEx(&OS_ARMv7M_MPU_API);

}

420 CHAPTER 22 API functions

22.6.6 OS_MPU_ExtendTaskContext()

Description

Extends the task context for the MPU registers.

Prototype

void OS_MPU_ExtendTaskContext(void);

Additional information

It is device dependent how many MPU regions are available. This function makes it possible

to use all MPU regions for every single task. Otherwise the tasks would have to share the

MPU regions. To do so the MPU register must be saved and restored with every context

switch.

This function allows the user to extend the task context for the MPU registers. A major

advantage is that the task extension is task-specific. This means that the additional MPU

that the task switching time of other tasks is not affected. The same is true for the required

stack space: Additional stack space is required only for the tasks which actually save the

additional MPU registers. The task context can be extended only once per task. The function

must not be called multiple times for one task.

OS_MPU_ExtendTaskContext() is not available in OS_LIBMODE_XR.

OS_SetDefaultContextExtension() can be used to automatically add MPU register to the

task context of every newly created task.

Example

static void HPTask(void) {

OS_MPU_ExtendTaskContext();

OS_MPU_SwitchToUnprivState();

while (1) {

OS_TASK_Delay(50);

}

static void HPTask(void) {

OS_MPU_ExtendTaskContext();

OS_MPU_SwitchToUnprivState();

while (1) {

OS_TASK_Delay(200);

}

Note

If you run more than one unprivileged task you must use OS_MPU_ExtendTaskCon-

text() in order to save and restore the MPU register for each unprivileged task.

421 CHAPTER 22 API functions

22.6.7 OS_MPU_GetThreadState()

Description

Returns the current privileged task state.

Prototype

OS_MPU_THREAD_STATE OS_MPU_GetThreadState(void);

Return value

0 Privileged state (OS_MPU_THREAD_STATE_PRIVILEGED).

1 Unprivileged state (OS_MPU_THREAD_STATE_UNPRIVILEGED).

Additional information

A new created task has the task state OS_MPU_THREAD_STATE_PRIVILEGED. It can be

set to OS_MPU_THREAD_STATE_UNPRIVILEGED with the API function OS_MPU_SwitchToUn-

privState(). A task can never set itself back to the privileged state OS_MPU_THREAD_S-

TATE_PRIVILEGED.

422 CHAPTER 22 API functions

22.6.8 OS_MPU_SetAllowedObjects()

Description

Sets a task specific list of objects to which the task has access via embOS API functions.

Prototype

void OS_MPU_SetAllowedObjects(OS_TASK* pTask,

OS_CONST_PTR OS_MPU_OBJ *pObjList);

Parameters

Parameter Description

pTask Pointer to a task control block.

pObjList Pointer to a list of allowed objects.

Additional information

Per default a task has neither direct nor indirect write access via embOS API functions to

any embOS object like a task control block. Even if the object is in the list of allowed objects

a direct write access to a control structure is not possible. But if an object is in the list the

task can access the object via embOS API functions. This can be e.g. the own task control

block, a mailbox control structure which is mutual used by different task or even the task

control block of another task. It is the developer responsibility to only add objects which

are necessary for the unprivileged task. The list is null-terminated which means the last

entry must always be: {NULL, OS_MPU_OBJTYPE_INVALID}.

The following object types exist:

OS_MPU_OBJTYPE_TASK

OS_MPU_OBJTYPE_MUTEX

OS_MPU_OBJTYPE_SEMA

OS_MPU_OBJTYPE_EVENT

OS_MPU_OBJTYPE_QUEUE

OS_MPU_OBJTYPE_MAILBOX

OS_MPU_OBJTYPE_SWTIMER

OS_MPU_OBJTYPE_MEMPOOL

OS_MPU_OBJTYPE_WATCHDOG

Example

static const OS_MPU_OBJ _ObjList[] = {{(OS_U32)&TCBHP, OS_MPU_OBJTYPE_TASK},

{(OS_U32)NULL, OS_MPU_OBJTYPE_INVALID}};

static void _Unpriv(void) {

OS_TASK_SetName(&TCBHP, "Segger");

while (1) {

OS_TASK_Delay(10);

}

static void HPTask(void) {

OS_MPU_ExtendTaskContext();

OS_MPU_SetAllowedObjects(&TCBHP, _ObjList);

OS_MPU_SwitchToUnprivState();

_Unpriv();

}

423 CHAPTER 22 API functions

22.6.9 OS_MPU_SetDeviceDriverList()

Description

Sets the device driver list.

Prototype

void OS_MPU_SetDeviceDriverList(OS_CONST_PTR OS_MPU_DEVICE_DRIVER_FUNC *pList);

Parameters

Parameter Description

pList Pointer to device driver function address list.

Additional information

All device driver function addresses are stored in one list. The last item must be NULL. A

device driver is called with the according index to this list.

Example

static const OS_MPU_DEVICE_DRIVER_FUNC _DeviceDriverList[] =

{ BSP_LED_DeviceDriver,

NULL }; // Last item must be NULL

void BSP_Init(void) {

OS_MPU_SetDeviceDriverList(_DeviceDriverList);

}

424 CHAPTER 22 API functions

22.6.10 OS_MPU_SetErrorCallback()

Description

Sets the MPU error callback function. This function is called when a task is suspended due

to an MPU fault.

Prototype

void OS_MPU_SetErrorCallback(OS_MPU_ERROR_CALLBACK pFunc);

Parameters

Parameter Description

pFunc Pointer to callback function.

Additional information

embOS suspends a task when it detects an invalid access. The internal error function OS_M-

PU_Error() calls the user callback function in order to inform the application. The applica-

tion can e.g. turn on an error LED or write the fault into a log file.

The callback function is called with the following parameter:

Parameter type Description

OS_TASK* Pointer to task control block of the unprivileged task which

caused the MPU error.

OS_MPU_ERRORCODE Error code which describes the cause for the MPU error.

Example

static void _ErrorCallback(OS_TASK* pTask, OS_MPU_ERRORCODE ErrorCode) {

printf("%s has been stopped due to error %d\n",

pTask->Name,

ErrorCode);

}

int main(void) {

OS_MPU_SetErrorCallback(&_ErrorCallback);

}

embOS-MPU error codes

Define Explanation

OS_MPU_ERROR_INVALID_REGION The OS object address is within an allowed task re-

gion. This is not allowed. This can for example hap-

pen when the object was placed on the task stack.

OS_MPU_ERROR_INVALID_OBJECT The unprivileged task is not allowed to access this

OS object.

OS_MPU_ERROR_INVALID_API

The unprivileged task tried to call an embOS API

function which is not valid for an unprivileged

task. For example unprivileged tasks must not call

OS_TASK_EnterRegion().

OS_MPU_ERROR_HARDFAULT Indicates that the task caused a hardfault.

OS_MPU_ERROR_MEMFAULT An illegal memory access was performed. A unprivi-

leged task tried to write memory without having the

access permission.

OS_MPU_ERROR_BUSFAULT Indicates that the task caused a bus fault.

425 CHAPTER 22 API functions

Define Explanation

OS_MPU_ERROR_USAGEFAULT Indicates that the task caused an usage fault.

OS_MPU_ERROR_SVC The supervisor call was not made within an embOS

API function. This is not allowed.

426 CHAPTER 22 API functions

22.6.11 OS_MPU_SwitchToUnprivState()

Description

Switches a task to unprivileged state.

Prototype

void OS_MPU_SwitchToUnprivState(void);

Additional information

The task code must be split into two parts. The first part runs in privileged state and ini-

tializes the embOS MPU settings. The second part runs in unprivileged state and is called

after the privileged part switched to the unprivileged state with OS_MPU_SwitchToUnprivS-

tate().

Example

static void _Unsecure(void) {

while (1) {

OS_TASK_Delay(10);

}

static void HPTask(void) {

// Initialization, e.g. add memory regions

OS_MPU_ExtendTaskContext();

OS_MPU_SwitchToUnprivState();

_Unsecure();

}

Note

If you run more than one unprivileged task you must use OS_MPU_ExtendTaskCon-

text() in order to save and restore the MPU register for each unprivileged task.

427 CHAPTER 22 API functions

22.6.12 OS_MPU_SwitchToUnprivStateEx()

Description

Switches a task to unprivileged state and calls a task function which runs on a separate

task stack. This is an extended handling which is used with ARMv8M only.

Prototype

void OS_MPU_SwitchToUnprivStateEx(voidRoutine* pRoutine,

void OS_STACKPTR *pStack,

OS_UINT StackSize);

Parameters

Parameter Description

pRoutine Pointer to a function that should run in unprivileged state.

pStack Pointer to the task stack which should be used in unprivi-

leged state.

StackSize Size of the task stack.

Additional information

The task code must be split into two parts. The first part runs in privileged state and initial-

izes the embOS MPU settings. The second part runs in unprivileged state and is called after

the privileged part switched to the unprivileged state with OS_MPU_SwitchToUnprivState-

Ex(). You must use OS_MPU_SwitchToUnprivStateEx() with ARMv8M only.

Example

static unsigned char _Stack[512];

static void _Unsecure(void) { // Runs on the stack _Stack

while (1) {

OS_TASK_Delay(10);

}

static void HPTask(void) {

// Initialization, e.g. add memory regions

OS_MPU_ExtendTaskContext();

OS_MPU_SwitchToUnprivStateEx(_Unsecure, _Stack, 512);

}

Note

If you run more than one unprivileged task you must use OS_MPU_ExtendTaskCon-

text() in order to save and restore the MPU register for each unprivileged task.

428 CHAPTER 22 API functions

22.6.13 OS_MPU_SetSanityCheckBuffer()

Description

Sets the pointer in the task control block to a buffer which holds a copy of the MPU register

for sanity check. The buffer size needs to be the size of all MPU register.

Prototype

void OS_MPU_SetSanityCheckBuffer(OS_TASK* pTask,

void* p);

Parameters

Parameter Description

pTask Pointer to the task control block.

pPointer to the MPU register buffer.

Additional information

OS_MPU_SetSanityCheckBuffer() is only available in OS_LIBMODE_SAFE which is used in

the certified embOS-MPU. Due to e.g. a hardware failure, a MPU register content could

change. A copy of all relevant MPU register is held in the buffer. OS_MPU_SanityCheck()

compares this copy to the actual MPU register and returns whether the register still have

the same value.

OS_MPU_SetSanityCheckBuffer() must be used prior to calling OS_MPU_SwitchToUn-

privState() only.

It must be called before OS_MPU_SanityCheck() is used for the first time. The size of the

buffer depends on the used hardware MPU. Appropiate defines are provided, e.g. OS_AR-

M_V7M_MPU_REGS_SIZE.

Example

static OS_U8 HPBuffer[OS_ARM_V7M_MPU_REGS_SIZE];

static void HPTask(void) {

OS_BOOL r;

OS_MPU_SetSanityCheckBuffer(&TCBHP, HPBuffer);

OS_MPU_ExtendTaskContext();

OS_MPU_SwitchToUnprivState();

while (1) {

r = OS_MPU_SanityCheck();

if (r == 0) {

while (1) { // MPU register value invalid

}

429 CHAPTER 22 API functions

22.6.14 OS_MPU_SanityCheck()

Description

Performs an MPU sanity check which checks if the MPU register still have the correct value.

Prototype

OS_BOOL OS_MPU_SanityCheck(void);

Return value

0 Failure, at least one register has not the correct value.

1 Success, all registers have the correct value.

Additional information

OS_MPU_SanityCheck() is only available in OS_LIBMODE_SAFE which is used in the certified

embOS-MPU. Due to e.g. a hardware failure, an MPU register content could change. A copy

of all relevant MPU register is held in a buffer and a pointer to this buffer is stored in the

according task control block. OS_MPU_SanityCheck() compares this copy to the actual MPU

OS_MPU_SanityCheck() must be used in unprivileged tasks after the call to OS_M-

PU_SwitchToUnprivState() only.

OS_MPU_SetSanityCheckBuffer() must be called before OS_MPU_SanityCheck() is used

for the first time. If the buffer is not set, OS_MPU_SanityCheck() will return 0.

Example

static OS_U8 HPBuffer[OS_ARM_V7M_MPU_REGS_SIZE];

static void HPTask(void) {

OS_BOOL r;

OS_MPU_SetSanityCheckBuffer(&TCBHP, HPBuffer);

OS_MPU_ExtendTaskContext();

OS_MPU_SwitchToUnprivState();

while (1) {

r = OS_MPU_SanityCheck();

if (r == 0) {

while (1) { // MPU register value invalid

}

Chapter 23

Stacks

431 CHAPTER 23 Introduction

23.1 Introduction

The stack is the memory area used for storing the return address of function calls, para-

meters, and local variables, as well as for temporary storage. Interrupt routines also use

the stack to save the return address and flag registers, except in cases where the CPU has a

separate stack for interrupt functions. Refer to the CPU & Compiler Specifics manual of em-

bOS documentation for details on your processor’s stack. A “normal” single-task program

needs exactly one stack. In a multitasking system, every task must have its own stack.

The stack needs to have a minimum size which is determined by the sum of the stack

usage of the routines in the worst-case nesting. If the stack is too small, a section of the

memory that is not reserved for the stack will be overwritten, and a serious program failure

is most likely to occur. Therefore, the debug and stack-check builds of embOS monitor the

stack size (and, if available, also interrupt stack size) and call OS_Error() if they detect

stack overflows.

To detect a stack overflow, the stack is filled with control characters upon its creation,

thereby allowing for a check on these characters every time a task is deactivated. However,

embOS does not guarantee to reliably detect all stack overflows. A stack that has been

defined larger than necessary, on the other hand, does no harm; even though it is a waste

of memory.

23.1.1 System stack

Before embOS takes control (before the call to OS_Start()), a program uses the socalled

system stack. This is the same stack that a non-embOS program for this CPU would use.

After transferring control to the embOS scheduler by calling OS_Start(), the system stack

is used for the following (when no task is executing):

• embOS scheduler

• embOS software timers (and the callback).

For details regarding required size of your system stack, refer to the CPU & Compiler

Specifics manual of embOS documentation.

23.1.2 Task stack

Each embOS task has a separate stack. The location and size of this stack is defined when

creating the task. The minimum size of a task stack depends on the CPU and the compiler.

For details, see the CPU & Compiler Specifics manual of embOS documentation.

23.1.3 Interrupt stack

To reduce stack size in a multitasking environment, some processors use a specific stack

area for interrupt service routines (called a hardware interrupt stack). If there is no interrupt

stack, you will need to add stack requirements of your interrupt service routines to each

task stack.

Even if the CPU does not support a hardware interrupt stack, embOS may support a separate

stack for interrupts by calling the function OS_INT_EnterIntStack() at beginning of an

interrupt service routine and OS_INT_LeaveIntStack() at its very end. In case the CPU

already supports hardware interrupt stacks or if a separate interrupt stack is not supported

at all, these function calls are implemented as empty macros.

We recommend using OS_INT_EnterIntStack() and OS_INT_LeaveIntStack() even if

there is currently no additional benefit for your specific CPU, because code that uses them

might reduce stack size on another CPU or a new version of embOS with support for an

interrupt stack for your CPU. For details about interrupt stacks, see the CPU & Compiler

Specifics manual of embOS documentation.

432 CHAPTER 23 Introduction

23.1.4 Stack size calculation

embOS includes stack size calculation routines. embOS fills the task stacks and also the

system stack and the interrupt stack with a pattern byte. embOS checks at runtime how

many bytes at the end of the stack still include the pattern byte. With it the amount of used

and unused stack can be calculated.

23.1.5 Stack-check

embOS includes stack-check routines. embOS fills the task stacks and also the system stack

and the interrupt stack with a pattern byte. embOS periodically checks whether the last

pattern byte at the end of the stack was overwritten and calls OS_Error() when it was.

433 CHAPTER 23 API functions

23.2 API functions

Routine Description

main

Task

ISR

Timer

OS_STACK_GetIntStackBase() Returns the base address of the inter-

rupt stack. ●●●●

OS_STACK_GetIntStackSize() Returns the size of the interrupt stack. ● ● ● ●

OS_STACK_GetIntStackSpace() Returns the amount of interrupt stack

which was never used (Free interrupt

stack space).

●●●●

OS_STACK_GetIntStackUsed() Returns the amount of interrupt stack

which is actually used. ●●●●

OS_STACK_GetTaskStackBase() Returns a pointer to the base of a task

stack. ●●●●

OS_STACK_GetTaskStackSize() Returns the total size of a task stack. ● ● ● ●

OS_STACK_GetTaskStackSpace() Returns the amount of task stack which

was never used by the task (Free stack

space).

●●●●

OS_STACK_GetTaskStackUsed() Returns the amount of task stack which

is actually used by the task. ●●●●

OS_STACK_GetSysStackBase() Returns the base address of the system

stack. ●●●●

OS_STACK_GetSysStackSize() Returns the size of the system stack. ● ● ● ●

OS_STACK_GetSysStackSpace() Returns the amount of system stack

which was never used (Free system

stack space).

●●●●

OS_STACK_GetSysStackUsed() Returns the amount of system stack

which is actually used. ●●●●

OS_STACK_SetCheckLimit() Sets the stack check limit to a percent-

aged value of the stack size. ● ●

OS_STACK_GetCheckLimit() Returns the stack check limit in percent. ● ●

434 CHAPTER 23 API functions

23.2.1 OS_STACK_GetIntStackBase()

Description

Returns a pointer to the base of the interrupt stack.

Prototype

void* OS_STACK_GetIntStackBase(void);

Return value

The pointer to the base address of the interrupt stack.

Additional information

This function is only available when an interrupt stack exists.

Example

void CheckIntStackBase(void) {

printf("Addr Interrupt Stack %p", OS_STACK_GetIntStackBase());

}

435 CHAPTER 23 API functions

23.2.2 OS_STACK_GetIntStackSize()

Description

Returns the size of the interrupt stack.

Prototype

unsigned int OS_STACK_GetIntStackSize(void);

Return value

The size of the interrupt stack in bytes.

Additional information

This function is only available when an interrupt stack exists.

Example

void CheckIntStackSize(void) {

printf("Size Interrupt Stack %u", OS_STACK_GetIntStackSize());

}

436 CHAPTER 23 API functions

23.2.3 OS_STACK_GetIntStackSpace()

Description

Returns the amount of interrupt stack which was never used (Free interrupt stack space).

Prototype

unsigned int OS_STACK_GetIntStackSpace(void);

Return value

Amount of interrupt stack which was never used in bytes.

Additional information

This function is only available in the debug and stack-check builds and when an interrupt

stack exists.

Note

This routine does not reliably detect the amount of stack space left, because it can

only detect modified bytes on the stack. Unfortunately, space used for register storage

or local variables is not always modified. In most cases, this routine will detect the

correct amount of stack bytes, but in case of doubt, be generous with your stack space

or use other means to verify that the allocated stack space is sufficient.

Example

void CheckIntStackSpace(void) {

printf("Unused Interrupt Stack %u", OS_STACK_GetIntStackSpace());

}

437 CHAPTER 23 API functions

23.2.4 OS_STACK_GetIntStackUsed()

Description

Returns the amount of interrupt stack which is actually used.

Prototype

unsigned int OS_STACK_GetIntStackUsed(void);

Return value

Amount of interrupt stack which is actually used in bytes.

Additional information

This function is only available in the debug and stack-check builds and when an interrupt

stack exists.

Note

This routine does not reliably detect the amount of stack space used, because it can

only detect modified bytes on the stack. Unfortunately, space used for register storage

or local variables is not always modified. In most cases, this routine will detect the

correct amount of stack bytes, but in case of doubt, be generous with your stack space

or use other means to verify that the allocated stack space is sufficient.

Example

void CheckIntStackUsed(void) {

printf("Used Interrupt Stack %u", OS_STACK_GetIntStackUsed());

}

438 CHAPTER 23 API functions

23.2.5 OS_STACK_GetTaskStackBase()

Description

Returns a pointer to the base of a task stack. If pTask is NULL, the currently executed task

is checked.

Prototype

void OS_STACKPTR *OS_STACK_GetTaskStackBase(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask The task whose stack base should be returned. NULL denotes

the current task.

Return value

Pointer to the base address of the task stack.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task.

This function is only available in the debug and stack-check builds of embOS, because only

these builds initialize the stack space used for the tasks.

Example

void CheckStackBase(void) {

printf("Addr Stack[0] %p", OS_STACK_GetTaskStackBase(&TCB[0]);

OS_TASK_Delay(1000);

printf("Addr Stack[1] %p", OS_STACK_GetTaskStackBase(&TCB[1]);

OS_TASK_Delay(1000);

}

439 CHAPTER 23 API functions

23.2.6 OS_STACK_GetTaskStackSize()

Description

Returns the total size of a task stack.

Prototype

unsigned int OS_STACK_GetTaskStackSize(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask The task whose stack size should be checked. NULL means

current task.

Return value

Total size of the task stack in bytes.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task.

This function is only available in the debug and stack-check builds of embOS, because only

these builds initialize the stack space used for the tasks.

Example

void CheckStackSize(void) {

printf("Size Stack[0] %u", OS_STACK_GetTaskStackSize(&TCB[0]);

OS_TASK_Delay(1000);

printf("Size Stack[1] %u", OS_STACK_GetTaskStackSize(&TCB[1]);

OS_TASK_Delay(1000);

}

440 CHAPTER 23 API functions

23.2.7 OS_STACK_GetTaskStackSpace()

Description

Returns the amount of task stack which was never used by the task (Free stack space). If

no specific task is addressed, the current task is checked.

Prototype

unsigned int OS_STACK_GetTaskStackSpace(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask The task whose stack space should be checked. NULL de-

notes the current task.

Return value

Amount of task stack which was never used by the task in bytes.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task.

In most cases, the stack size required by a task cannot be easily calculated because it takes

quite some time to calculate the worst-case nesting and the calculation itself is difficult.

However, the required stack size can be calculated using the function OS_STACK_GetTaskS-

tackSpace(), which returns the number of unused bytes on the stack. If there is a lot of

space left, you can reduce the size of this stack. This function is only available in the debug

and stack-check builds of embOS.

Note

This routine does not reliably detect the amount of stack space left, because it can

only detect modified bytes on the stack. Unfortunately, space used for register storage

or local variables is not always modified. In most cases, this routine will detect the

correct amount of stack bytes, but in case of doubt, be generous with your stack space

or use other means to verify that the allocated stack space is sufficient.

Example

void CheckStackSpace(void) {

printf("Unused Stack[0] %u", OS_STACK_GetTaskStackSpace(&TCB[0]);

OS_TASK_Delay(1000);

printf("Unused Stack[1] %u", OS_STACK_GetTaskStackSpace(&TCB[1]);

OS_TASK_Delay(1000);

}

441 CHAPTER 23 API functions

23.2.8 OS_STACK_GetTaskStackUsed()

Description

Returns the amount of task stack which is actually used by the task. If no specific task is

addressed, the current task is checked.

Prototype

unsigned int OS_STACK_GetTaskStackUsed(OS_CONST_PTR OS_TASK *pTask);

Parameters

Parameter Description

pTask The task whose stack usage should be checked. NULL de-

notes the current task.

Return value

Amount of task stack which is actually used by the task in bytes.

Additional information

If NULL is passed for pTask, the currently running task is used. However, NULL must not be

passed for pTask from main(), a timer callback or from an interrupt handler. A debug build

of embOS will call OS_Error() in case pTask does not indicate a valid task.

In most cases, the stack size required by a task cannot be easily calculated, because it takes

quite some time to calculate the worst-case nesting and the calculation itself is difficult.

However, the required stack size can be calculated using the function OS_STACK_GetTaskS-

tackUsed(), which returns the number of used bytes on the stack. If there is a lot of space

left, you can reduce the size of this stack. This function is only available in the debug and

stack-check builds of embOS.

Note

This routine does not reliably detect the amount of stack space used, because it can

only detect modified bytes on the stack. Unfortunately, space used for register storage

or local variables is not always modified. In most cases, this routine will detect the

correct amount of stack bytes, but in case of doubt, be generous with your stack space

or use other means to verify that the allocated stack space is sufficient.

Example

void CheckStackUsed(void) {

printf("Used Stack[0] %u", OS_STACK_GetTaskStackUsed(&TCB[0]);

OS_TASK_Delay(1000);

printf("Used Stack[1] %u", OS_STACK_GetTaskStackUsed(&TCB[1]);

OS_TASK_Delay(1000);

}

442 CHAPTER 23 API functions

23.2.9 OS_STACK_GetSysStackBase()

Description

Returns a pointer to the base of the system stack.

Prototype

void* OS_STACK_GetSysStackBase(void);

Return value

The pointer to the base address of the system stack.

Example

void CheckSysStackBase(void) {

printf("Addr System Stack %p", OS_STACK_GetSysStackBase());

}

443 CHAPTER 23 API functions

23.2.10 OS_STACK_GetSysStackSize()

Description

Returns the size of the system stack.

Prototype

unsigned int OS_STACK_GetSysStackSize(void);

Return value

The size of the system stack in bytes.

Example

void CheckSysStackSize(void) {

printf("Size System Stack %u", OS_STACK_GetSysStackSize());

}

444 CHAPTER 23 API functions

23.2.11 OS_STACK_GetSysStackSpace()

Description

Returns the amount of system stack which was never used (Free system stack space).

Prototype

unsigned int OS_STACK_GetSysStackSpace(void);

Return value

Amount of unused system stack, in bytes.

Additional information

This function is only available in the debug and stack-check builds of embOS.

Note

This routine does not reliably detect the amount of stack space left, because it can

only detect modified bytes on the stack. Unfortunately, space used for register storage

or local variables is not always modified. In most cases, this routine will detect the

correct amount of stack bytes, but in case of doubt, be generous with your stack space

or use other means to verify that the allocated stack space is sufficient.

Example

void CheckSysStackSpace(void) {

printf("Unused System Stack %u", OS_STACK_GetSysStackSpace());

}

445 CHAPTER 23 API functions

23.2.12 OS_STACK_GetSysStackUsed()

Description

Returns the amount of system stack which is actually used.

Prototype

unsigned int OS_STACK_GetSysStackUsed(void);

Return value

Amount of used system stack, in bytes.

Additional information

This function is only available in the debug and stack-check builds of embOS.

Note

This routine does not reliably detect the amount of stack space used, because it can

only detect modified bytes on the stack. Unfortunately, space used for register storage

or local variables is not always modified. In most cases, this routine will detect the

correct amount of stack bytes, but in case of doubt, be generous with your stack space

or use other means to verify that the allocated stack space is sufficient.

Example

void CheckSysStackUsed(void) {

printf("Used System Stack %u", OS_STACK_GetSysStackUsed());

}

446 CHAPTER 23 API functions

23.2.13 OS_STACK_SetCheckLimit()

Description

Sets the stack check limit to a percentaged value of the stack size.

Prototype

void OS_STACK_SetCheckLimit(OS_U8 Limit);

Parameters

Parameter Description

Limit Stack check limit in percent. Valid values are 0..100%.

Values above 100% are trimmed to 100%.

Additional information

This function is only available in safety builds of embOS (OS_LIBMODE_SAFE). In all other

embOS builds the stack check limit is fixed to 100%. It can be used to set the stack check

limit to a value which triggers the error condidition before the stack is filled completely. With

the safety build of embOS the application can react before the stack actually overflows.

Note

This routine must only be called from main() or privileged tasks. This setting is jointly

used for the system stack, the interrupt stack and all task stacks. The best practice

is to call it in main() before OS_Start().

Example

int main(void) {

OS_Init();

OS_InitHW();

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_STACK_SetCheckLimit(70); // Set the stack check limit to 70%

OS_Start();

}

447 CHAPTER 23 API functions

23.2.14 OS_STACK_GetCheckLimit()

Description

Returns the stack check limit in percent.

Prototype

OS_U8 OS_STACK_GetCheckLimit(void);

Return value

The stack check limit as a percentaged value of the stack size.

Additional information

This function is only available in safety builds of embOS (OS_LIBMODE_SAFE). In all other

embOS builds the stack check limit is fixed to 100%.

Note

This routine must only be called from main() or privileged tasks. This setting is jointly

used for the system stack, the interrupt stack and all task stacks.

Chapter 24

Board Support Packages

449 CHAPTER 24 Introduction

24.1 Introduction

This chapter explains the target system specific parts of embOS, called BSP (board support

package). If the software is up and running on your target system, there is no need to

read this chapter.

In general, no configuration is required to get started with embOS: The start projects

supplied with your embOS shipment will execute on your system. Small modifications to

the configuration might be necessary at a later point, for example to configure a different

system frequency or in order to enable a UART for the optional communication with em-

bOSView.

All hardware-specific routines that may require modifications are located in one of two

source files delivered with embOS. The file RTOSInit.c is provided in source code and con-

tains most of the functions that may require modifications to match your target hardware.

Furthermore, the file BSP.c is provided in source code as well and may contain routines to

initialize and control LEDs, which may require further modifications to match your target

hardware.

The sole exception to this rule is that some ports of embOS require an additional interrupt

vector table file. Further details on these are available with the CPU & Compiler Specifics

manual of the embOS documentation.

450 CHAPTER 24 Hardware-speciﬁc routines

24.2 Hardware-specific routines

The following routines are not exposed as user API, but are instead required by embOS for

internal usage. They are shipped as source code to allow for modifications to match your

actual target hardware. However, unless explicitly stated otherwise, these functions must

not be called from your application.

Routine Description

main

Task

ISR

Timer

Required for embOS

OS_ConvertCycles2us() Converts cycles into microseconds. ● ● ● ●

OS_GetTime_Cycles() Reads the timestamp in cycles.

OS_Idle() The idle loop is executed whenever no task is

ready for execution.

OS_InitHW() Initializes the hardware required for embOS to

run. ●

SysTick_Handler() The embOS timer interrupt handler.

Optional for run-time embOSView

OS_COM_Init() Initializes communication with embOSView. ●

OS_COM_Send1() Sends one character towards embOSView.

OS_ISR_Rx() Receive interrupt handler for UART communica-

tion with embOSView.

OS_ISR_Tx() Transmit interrupt handler for UART communi-

cation with embOSView.

451 CHAPTER 24 Hardware-speciﬁc routines

24.2.1 OS_ConvertCycles2us()

Description

Converts clock cycles into microseconds.

Prototype

OS_U32 OS_ConvertCycles2us(OS_U32 Cycles);

Parameters

Parameter Description

Cycles Number of CPU cycles to convert.

Return value

The period of time in microseconds that is equivalent to the given number of clock cycles

as a 32 bit unsigned integer value.

Additional information

This function is required for profiling and high resolution time measurement. You must

modify it when using different clock settings (see Setting the system frequency OS_FSYS

on page 461).

452 CHAPTER 24 Hardware-speciﬁc routines

24.2.2 OS_GetTime_Cycles()

Description

Returns the system time in timer clock cycles. Cycle length depends on the system.

Prototype

OS_U32 OS_GetTime_Cycles(void);

Return value

The number of clock cycles that have passed since the last reset as a 32 bit unsigned

integer value.

Additional information

Interrupts must be disabled prior to calling this function. This function is required for pro-

filing and high resolution time measurement. You must modify it when using different clock

settings (see Setting the system frequency OS_FSYS on page 461).

453 CHAPTER 24 Hardware-speciﬁc routines

24.2.3 OS_Idle()

Description

The function OS_Idle() is called when no task, timer routine or ISR is ready for execution.

Usually, OS_Idle() is programmed as an endless loop without any content. With many

embOS start projects, however, it activates a power save mode of the target CPU (see

Starting power save modes in OS_Idle() on page 303).

Prototype

void OS_Idle(void);

Additional information

OS_Idle() is not a task, it neither has a task context nor a dedicated stack. Instead, it

runs on the system’s C stack, which is also used by the kernel. Exceptions and interrupts

occurring during OS_Idle() will return to OS_Idle() unless they trigger a task switch. When

returning to OS_Idle(), execution is continued from where it was interrupted. However, in

case a task switch did occur during execution of OS_Idle(), the function is abandoned and

execution will start from the beginning when it is activated again. Hence, no functionality

should be implemented that relies on the stack to be preserved. If this is required, please

consider implementing a custom idle task (Creating a custom Idle task on page 454).

Calling OS_TASK_EnterRegion() and OS_TASK_LeaveRegion() from OS_Idle() allows to

inhibit task switches during the execution of OS_Idle(). Running in a critical region does

not block interrupts, but disables task switches until OS_TASK_LeaveRegion() is called.

Using a critical region during OS_Idle() will therefore affect task activation time, but will

not affect interrupt latency.

Example

void OS_Idle(void) { // Idle loop: No task is ready to execute

while (1) {

}

454 CHAPTER 24 Hardware-speciﬁc routines

24.2.3.1 Creating a custom Idle task

As an alternative to OS_Idle(), it is also possible to create a custom “idle task”. This task

must run as an endless loop at the lowest task priority within the system. If no blocking

function is called from that task, the system will effectively never enter OS_Idle(), but will

execute this task instead whenever no other task is ready for execution.

Example

#include "RTOS.h"

#include "BSP.h"

static OS_STACKPTR int StackHP[128], StackLP[128], StackIdle[128];

static OS_TASK TCBHP, TCBLP, TCBIdle;

static void HPTask(void) {

while (1) {

BSP_ToggleLED(0);

OS_TASK_Delay(50);

}

static void LPTask(void) {

while (1) {

BSP_ToggleLED(1);

OS_TASK_Delay(200);

}

static void IdleTask(void) {

while (1) {

// Perform idle duty, e.g.

// - Switch off clocks for unused peripherals.

// - Free resources that are no longer used by any task.

// - Enter power save mode.

}

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize hardware for embOS

BSP_Init(); // Initialize LED ports

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_TASK_CREATE(&TCBIdle, "Idle Task", 1, IdleTask, StackIdle);

OS_Start(); // Start multitasking

return 0;

}

455 CHAPTER 24 Hardware-speciﬁc routines

24.2.4 OS_InitHW()

Description

Initializes the hardware required for embOS to run. embOS needs a timer interrupt to

determine when to activate tasks that wait for the expiration of a delay, when to call a

software timer, and to keep the time variable up-to-date.

This function must be called once during main().

Prototype

void OS_InitHW(void);

Additional information

You must modify this routine when a different hardware timer should be used (see Using a

different timer to generate tick interrupts for embOS on page 461).

With most embOS start projects, this routine may also call further, optional configuration

functions, e.g. for

• configuration of the embOS microsecond precise system time parameters (see

OS_TIME_ConfigSysTimer()), and

• initialization of the communication interface to be used with embOSView (see

OS_COM_Init()).

456 CHAPTER 24 Hardware-speciﬁc routines

24.2.5 SysTick_Handler()

Description

The embOS system timer tick interrupt handler.

Prototype

void SysTick_Handler(void);

Additional information

With specific embOS start projects, this handler may be implemented using a device specific

interrupt name. When using a different timer, always check the specified interrupt vector.

457 CHAPTER 24 Hardware-speciﬁc routines

24.2.6 OS_COM_Init()

Description

Initializes the communication channel for embOSView. This function usually is called once

during OS_InitHW().

Prototype

void OS_COM_Init(void);

Additional information

You must modify this routine according to your communication interface. For example when

a different UART or baudrate should be used for communication with embOSView. (see

Using a different UART or baudrate for embOSView on page 461).

To select a communications interface other than UART, refer to Select the communication

channel on page 379.

458 CHAPTER 24 Hardware-speciﬁc routines

24.2.7 OS_COM_Send1()

Description

Sends one character towards embOSView via the configured interface.

Prototype

void OS_COM_Send1(OS_U8 c);

Parameters

Parameter Description

cThe character to send towards embOSView.

Additional information

This function is required for OS_COM_SendString() (see OS_COM_SendString()).

You must modify this routine according to your communication interface. Using a different

UART or baudrate for embOSView on page 461).

To select a communications interface other than UART, refer to Select the communication

channel on page 379.

459 CHAPTER 24 Hardware-speciﬁc routines

24.2.8 OS_ISR_Rx()

Description

Receive interrupt handler for UART communication with embOSView.

Prototype

void OS_ISR_Rx(void);

Additional information

You must modify this routine when UART is selected as communications interface but a

different UART should be used for communication with embOSView. With specific embOS

start projects, this handler may be implemented using a device specific interrupt name.

Furthermore, with specific devices UART interrupts may share a common interrupt source.

In that case, OS_ISR_Rx() and OS_ISR_Tx() are implemented as a single interrupt handler

that may utilize a device specific interrupt name.

When using a different communications interface, this routine is not used.

460 CHAPTER 24 Hardware-speciﬁc routines

24.2.9 OS_ISR_Tx()

Description

Transmit interrupt handler for UART communication with embOSView.

Prototype

void OS_ISR_Tx(void);

Additional information

You must modify this routine when UART is selected as communications interface but a

different UART should be used for communication with embOSView. With specific embOS

start projects, this handler may be implemented using a device specific interrupt name.

Furthermore, with specific devices the UART interrupts may share a common interrupt

source. In that case, OS_ISR_Rx() and OS_ISR_Tx() are implemented as a single interrupt

handler that may utilize a device specific interrupt name.

When using a different communications interface, this routine is not used.

461 CHAPTER 24 How to change settings

24.3 How to change settings

24.3.1 Setting the system frequency OS_FSYS

Relevant defines

•OS_FSYS (System frequency in Hz)

Relevant routines

•OS_ConvertCycles2us()

•OS_GetTime_Cycles()

•OS_InitHW()

OS_FSYS defines the clock frequency of your system in Hz (times per second). The value

of OS_FSYS is used to calculate the desired reload counter value for the system timer for

1000 interrupts / sec. The interrupt frequency therefore typically is 1 kHz.

Different (lower or higher) interrupt rates are possible. If you choose an interrupt frequency

different from 1 kHz, the value of the time variable OS_Global.Time will no longer be

equivalent to multiples of 1 msec (see OS_Global.Time on page 464). However, if you

use a multiple of 1 msec as tick time, the basic time unit can be made 1 msec by using the

function OS_TICK_Config() (see OS_TICK_Config()). The basic time unit does not need

to be 1 msec; it might just as well be 100 usec or 10 msec or any other value. For most

applications, however, 1 msec is an appropriate value.

24.3.2 Using a different timer to generate tick interrupts for

embOS

Relevant routines

•OS_InitHW()

embOS usually generates one interrupt per msec, making the timer interrupt, or tick, nor-

mally equal to 1 msec. This is done by a timer initialized in the routine OS_InitHW(). If you

want to use a different timer for your application, you must modify OS_InitHW() to initialize

the appropriate timer. For details about initialization, read the comments in RTOSInit.c.

24.3.3 Using a different UART or baudrate for embOSView

Relevant defines

•OS_UART (Selection of UART to be used with embOSView, -1 to disable)

•OS_BAUDRATE (Selection of baudrate for communication with embOSView)

Relevant routines:

•OS_COM_Init()

•OS_COM_Send1()

•OS_ISR_Rx()

•OS_ISR_Tx()

In some cases, this may be done by simply changing the define OS_UART. Refer to the

contents of the RTOSInit.c file for more information about which UARTS have been pre-

configured for your target hardware.

Chapter 25

System Variables

463 CHAPTER 25 Introduction

25.1 Introduction

The system variables are described here for a deeper understanding of how the OS works

and to make debugging easier.

Not all embOS internal variables are explained here as they are not required to use embOS.

Your application should not rely on any of the internal variables, as only the documented

API functions are guaranteed to remain unchanged in future versions of embOS.

These variables are accessible, but they should only be altered by functions of embOS.

However, some of these variables can be very useful, especially the time variables.

Note

Do not alter any system variables!

464 CHAPTER 25 Time variables

25.2 Time variables

25.2.1 OS_Global

OS_Global is a structure which includes embOS internal variables. The following vari-

ables OS_Global.Time and OS_Global.TimeDex are part of OS_Global. Any other part of

OS_Global is not explained here as they are not required to use embOS.

25.2.2 OS_Global.Time

Description

This is the time variable which contains the current system time in embOS system ticks

(typically equivalent to msec).

Additional information

The time variable has a resolution of one time unit, which is normally 1/1000 sec (1 msec)

and is normally the time between two successive calls to the embOS timer interrupt handler.

Instead of accessing this variable directly, use OS_TIME_GetTicks() or OS_TIME_GetTick-

s32() as explained in the Chapter Time Measurement on page 284.

25.2.3 OS_Global.TimeDex

For internal use only. Contains the time at which the next task switch or timer activation is

due. If ((int)(OS_Global.Time - OS_Global.TimeDex)) # 0, the task list and timer list

will be checked for a task or timer to activate. After activation, OS_Global.TimeDex will be

assigned the time stamp of the next task or timer to be activated.

Note that the value of OS_Global.TimeDex may be invalid during task execution. It con-

tains correct values during execution of OS_Idle() and when used internally in the embOS

scheduler. The value of OS_Global.TimeDex should not be used by the application.

If you need any information about the next time-scheduled action from embOS, the function

OS_TICKLESS_GetNumIdleTicks() can be used to get the number of system ticks spent

idle.

465 CHAPTER 25 OS information routines

25.3 OS information routines

Routine Description

main

Task

ISR

Timer

OS_INFO_GetCPU() Returns the CPU name. ● ● ● ●

OS_INFO_GetLibMode() Returns the library mode. ● ● ● ●

OS_INFO_GetLibName() Returns the library name. ● ● ● ●

OS_INFO_GetModel() Returns the memory model name. ● ● ● ●

OS_INFO_GetVersion() Returns the embOS version number. ● ● ● ●

466 CHAPTER 25 OS information routines

25.3.1 OS_INFO_GetCPU()

Description

Returns the CPU name.

Prototype

char *OS_INFO_GetCPU(void);

Return value

Char pointer to a null-terminated string containing the CPU name.

467 CHAPTER 25 OS information routines

25.3.2 OS_INFO_GetLibMode()

Description

Returns the library mode.

Prototype

char *OS_INFO_GetLibMode(void);

Return value

Char pointer to a null-terminated string containing the embOS library mode, e.g. “DP”, “R”

or “SP”.

468 CHAPTER 25 OS information routines

25.3.3 OS_INFO_GetLibName()

Description

Returns the library name.

Prototype

char *OS_INFO_GetLibName(void);

Return value

Char pointer to a null-terminated string containing the complete embOS library name,

memory model and library mode, e.g. “v7vLDP”.

469 CHAPTER 25 OS information routines

25.3.4 OS_INFO_GetModel()

Description

Returns the memory model name.

Prototype

char *OS_INFO_GetModel(void);

Return value

Char pointer to a null-terminated string containing the embOS memory model string, e.g.

“v7vL”.

470 CHAPTER 25 OS information routines

25.3.5 OS_INFO_GetVersion()

Description

Returns the embOS version number.

Prototype

OS_UINT OS_INFO_GetVersion(void);

Return value

Returns the embOS version number, e.g. “41203” for embOS version 4.12c.

Chapter 26

Supported Development Tools

472 CHAPTER 26 Overview

26.1 Overview

embOS has been developed with and for a specific C compiler version for the selected target

processor. Check the file RELEASE.HTML for details. It works with the specified C compiler

only, because other compilers may use different calling conventions (incompatible object

file formats) and therefore might be incompatible. However, if you prefer to use a different

C compiler, contact us and we will do our best to satisfy your needs in the shortest possible

time.

Reentrance

All routines that can be used from different tasks at the same time must be fully reentrant.

A routine is in use from the moment it is called until it returns or the task that has called

it is terminated.

All routines supplied with your real-time operating system are fully reentrant. If for some

reason you need to have non-reentrant routines in your program that can be used from

more than one task, it is recommended to use a mutex to avoid this kind of problem.

C routines and reentrance

Normally, the C compiler generates code that is fully reentrant. However, the compiler may

have options that force it to generate non-reentrant code. It is recommended not to use

these options, although it is possible to do so in certain circumstances.

Assembly routines and reentrance

As long as assembly functions access local variables and parameters only, they are fully

reentrant. Everything else needs to be thought about carefully.

Chapter 27

Source Code

474 CHAPTER 27 Introduction

27.1 Introduction

embOS is available in two versions:

1. Object version: Object code + hardware initialization source.

2. Full source version: Complete source code.

Because this document describes the object version, the internal data structures are not

explained in detail. The object version offers the full functionality of embOS including all

supported memory models of the compiler, the debug libraries as described and the source

code for idle task and hardware initialization. However, the object version does not allow

source-level debugging of the library routines and the kernel.

The full source version gives you complete flexibility: embOS can be recompiled for different

data sizes; different compile options give you full control of the generated code, making it

possible to optimize the system for versatility or minimum memory requirements. You can

debug the entire system and even modify it for new memory models or other CPUs.

The source code distribution of embOS contains the following additional files:

• The CPU folder contains all CPU and compiler-specific source code and header files used

for building the embOS libraries. Generally, you should not modify any of the files in

the CPU folder.

• The GenOSSrc folder contains all generic embOS sources.

• The embOS libraries can be rebuild with the additional batch files in the root folder. All

of them are described in the following section.

475 CHAPTER 27 Building embOS libraries

27.2 Building embOS libraries

The embOS libraries can only be built if you have licensed a source code version of embOS.

In the root path of embOS, you will find a DOS batch file Prep.bat, which needs to be

modified to match the installation directory of your C compiler. Once this is done, you can

call the batch file M.bat to build all embOS libraries and RTOS.h for your CPU.

The build process should run without any error or warning message. If the build process

reports any problem, check the following:

• Are you using the same compiler version as mentioned in the file Release.html?

• Can you compile a simple test file after running Prep.bat and does it really use the

compiler version you have specified?

• Is there anything mentioned about possible compiler warnings in the Release.html?

If you still have a problem, let us know.

The whole build process is controlled with a small number of batch files which are located

in the root directory of your source code distribution:

•ASM.bat: This batch file calls the assembler and is used for assembling the assembly

part of embOS which contains the task switch functionality. This file is called from the

embOS internal batch file CC_OS.bat and cannot be called directly.

•ASM_CPU.bat: This batch file is used to compile additional assembler files in the CPU/

OSSrcCPU folder. ASM_CPU.bat cannot be called directly.

•CC.bat: This batch file calls the compiler and is used for compiling one embOS source

file without debug information output. Most compiler options are defined in this file and

generally should not be modified. For your purposes, you might activate debug output

and may also modify the optimization level. All modifications should be done with care.

This file is called from the embOS internal batch file CC_OS.bat and cannot be called

directly.

•CC_CPU.bat: This batch file is used to compile additional C files in the CPU/OSSrcCPU

folder. CC_CPU.bat cannot be called directly.

•CCD.bat: This batch file calls the compiler and is used for compiling OS_Global.c which

contains all global variables. All compiler settings are identical to those used in CC.bat,

except debug output is activated to enable debugging of global variables when using

embOS libraries. This file is called from the embOS internal batch file CC_OS.bat and

cannot be called directly.

•Clean.bat: Deletes the entire output of the embOS library build process. It is called

during the build process, before new libraries are generated. It deletes the Start folder.

Therefore, be careful not to call this batch file accidentally. This file is called initially by

M.bat during the build process of all libraries.

•M.bat: This batch file must be called to rebuild all embOS libraries and RTOS.h. It

initially calls Clean.bat and therefore deletes the previous libraries and RTOS.h.

•M1.bat: This batch file is called from M.bat and is used for building one specific embOS

library, it cannot be called directly.

•MakeH.bat: Builds the embOS header file RTOS.h which is composed from the CPU/

compiler-specific part OS_Chip.h and the generic part OS_RAW.h. RTOS.h is output in

the subfolder Start\Inc.

•Prep.bat: Sets up the environment for the compiler, assembler, and linker. Ensure

that this file sets the path and additional include directories which are needed for your

compiler. This batch file is the only one which might require modifications to build the

embOS libraries. This file is called from M.bat during the build process of all libraries.

476 CHAPTER 27 Compile time switches

27.3 Compile time switches

Many features of embOS may be modified using compile-time switches. With each embOS

distribution, these switches are preconfigured to appropriate values for each embOS library

mode. In case a configuration set is desired that was not covered by the shipped embOS

libraries, the compile-time switches may be modified accordingly to create customized con-

figurations on your own authority. The embOS source code is necessary in order to do so.

According modifications must not be done to OS_RAW.h or RTOS.h, instead compile-time

switches must be added to OS_Config.h or configured as preprocessor definitions. Subse-

quently, the embOS sources must be recompiled to reflect the modified switches. In case

of doubt, please contact the embOS support for assistance. The default values depend on

the used library mode and are given in the following table for library mode OS_LIBMODE_DP.

Compile time switch Description Permitted

values Default

OS_DEBUG Enables runtime debug

checks

0: Disabled

1: Enabled 1

OS_DEBUG_LEVEL Enables additional debug

checks

1: Stan-

dard debug

code

2: Extend-

ed debug

code

OS_CHECKSTACK Performs stack checks

0: Disabled

1: Enabled

2: Stack

check with

config-

urable

stack check

limit

OS_STACKCHECK_LIMIT Percentage of stack us-

age that will be detected

as a stack overflow error

1-100 100

OS_PROFILE Profiling support 0: Disabled

1: Enabled 1

OS_SUPPORT_TICKSTEP embOSView tick step

support

0: Disabled

1: Enabled 1

OS_TRACE embOSView trace sup-

port

0: Disabled

1: Enabled 0

OS_TRACE_RECORD_API_END Generates additional

SystemView API-End

events

0: Disabled

1: Enabled 1

OS_RR_SUPPORTED Round-Robin supported 0: Disabled

1: Enabled 1

OS_TRACKNAME Allows task and OS ob-

ject names

0: Disabled

1: Enabled 1

OS_SUPPORT_SAVE_RESTORE_HOOK Support task context ex-

tensions

0: Disabled

1: Enabled 1

OS_SUPPORT_STAT Generate task statistic

information

0: Disabled

1: Enabled 1

OS_SUPPORT_PTLS Support for thread local

storage

0: Disabled

1: Enabled 1

OS_INIT_EXPLICITLY Initialization of internal

embOS variables

0: Disabled

1: Enabled 0

477 CHAPTER 27 Compile time switches

Compile time switch Description Permitted

values Default

OS_SUPPORT_TIMER Support for embOS soft-

ware timers

0: Disabled

1: Enabled 1

OS_SUPPORT_TICKLESS Support for embOS tick-

less mode

0: Disabled

1: Enabled 1

OS_SUPPORT_PERIPHERAL_POWER_CTRL Enables peripheral power

control

0: Disabled

1: Enabled 1

OS_POWER_NUM_COUNTERS Number of peripherals

which can be used > 0 5

OS_SPINLOCK_MAX_CORES Number of cores that

should access a spinlock > 0 4

OS_SUPPORT_OS_ALLOC Support for embOS

thread safe heap alloca-

tion

0: Disabled

1: Enabled 1

478 CHAPTER 27 Source code project

27.4 Source code project

All embOS start projects use the embOS libraries instead of the embOS source code. Even

the embOS source shipment does not include a project which uses embOS sources.

It can be useful to have the embOS sources instead of the embOS library in a project, e.g.

for easier debugging. To do so you just have to exclude or delete the embOS library from

your project and add the embOS sources as described below.

The embOS sources consists of the files in the folder GenOSSrc, CPU and CPU\OSSrcCPU.

These files can be found in the embOS source shipment.

Folder Description

GenOSSrc embOS generic sources

CPU RTOS assembler file

CPU\OSSrcCPU CPU and compiler-specific files

Please add all C and assembler files from these folders to your project and add include

paths to these folders to your project settings. For some embOS ports it might be necessary

to add additional defines to your preprocessor settings. If necessary you will find more

information about it in the CPU and compiler-specific embOS manual.

Chapter 28

Shipment

This chapter describes the different embOS shipment variants.

480 CHAPTER 28 General information

28.1 General information

embOS is available in three different variants: Free, Library, and Source code. The fully

functional free variant can easily be downloaded for each embOS port and has no technical

limitation.

The following table lists the included features with each of these variants:

Features Free Library Source code

embOS libraries ● ● ●

embOS source code ●

embOSView - Profiling PC tool ● ● ●

embOS manual ● ● ●

CPU/Compiler specific manual ● ● ●

Release notes ● ● ●

embOS IDE plug-ins ● ● ●

Board support packages ● ● ●

Feature & maintenance updates ● ●

Technical support ● ●

Free for any non-commercial use ●

481 CHAPTER 28 Library variant

28.2 Library variant

Directory File Description

Start\BoardSupport Board support packages in ven-

dor specific subfolders

Start\Inc RTOS.h, BSP.h, OS_Config.h Including files for embOS

Start\Lib embOS libraries

embOSView.exe PC utility for runtime analysis

JLinkARM.dll J-Link DLL used with embOSView

Release_embOS.html embOS release history

Release_embOS_CPU_Compil-

er.html embOS CPU and compiler-specif-

ic release history

SYSVIEW_embOS.txt SytemView ID descripton file

UM010xx_embOS_CPU_Compil-

er.pdf embOS CPU and compiler-specif-

ic manual

UM01001_embOS.pdf embOS manual

482 CHAPTER 28 Free variant

28.3 Free variant

The Free variant is identical to the library variant, exept for additional license information

governing the use of this variant.

Directory File Description

Start\BoardSupport Board support packages in ven-

dor specific subfolders

Start\Inc RTOS.h, BSP.h, OS_Config.h Including files for embOS

Start\Lib embOS libraries

embOSView.exe PC utility for runtime analysis

JLinkARM.dll J-Link DLL used with embOSView

License.txt License information

Release_embOS.html embOS release history

Release_embOS_CPU_Compil-

er.html embOS CPU and compiler-specif-

ic release history

SYSVIEW_embOS.txt SytemView ID descripton file

UM010xx_embOS_CPU_Compil-

er.pdf embOS CPU and compiler-specif-

ic manual

UM01001_embOS.pdf embOS manual

483 CHAPTER 28 Source code variant

28.4 Source code variant

The source code variant is identical to the library variant, but in addition also contains the

embOS source files and a set of batch files that can be used to rebuild the embOS libraries.

Directory File Description

CPU OSCHIP.h, OS_Priv.h,

RTOS.asm CPU- and compiler-specific files

CPU\OSSrcCPU Additional CPU- and compil-

er-specific source files

GenOSSrc Generic source files

Start\BoardSupport Board support packages in ven-

dor specific subfolders

Start\Inc RTOS.h, BSP.h, OS_Config.h Including files for embOS

Start\Lib embOS libraries

embOSView.exe PC utility for runtime analysis

JLinkARM.dll J-Link DLL used with embOSView

Release_embOS.html embOS release history

Release_embOS_CPU_Compil-

er.html embOS CPU and compiler-specif-

ic release history

SYSVIEW_embOS.txt SytemView ID descripton file

UM010xx_embOS_CPU_Compil-

er.pdf embOS CPU and compiler-specif-

ic manual

UM01001_embOS.pdf embOS manual

*.bat Batch files to rebuild the embOS

libraries

Chapter 29

Update

485 CHAPTER 29 Introduction

29.1 Introduction

This chapter describes how to update an existing project with a newer embOS version.

embOS ports are available for different CPUs and compiler. Each embOS port has its own

version number.

SEGGER updates embOS ports to a newer software version for different reasons. This is

done to fix problems or to include the newest embOS features.

Customers which have a valid support and update agreement will be automatically informed

about a new software version via email and may subsequently download the updated soft-

ware from www.myaccount.segger.com. The version information and release history is also

available at www.segger.com.

486 CHAPTER 29 How to update an existing project

29.2 How to update an existing project

If an existing project should be updated to a later embOS version, only files have to be

replaced.

Note

Do not use embOS files from different embOS versions in your project!

You should have received the embOS update as a zip file. Unzip this file to the location

of your choice and replace all embOS files in your project with the newer files from the

embOS update shipment.

For an easier update procedure, we recommend to not modify the files shipped with embOS.

In case these need to be updated, you will have to merge your modifications into the most

recent shipment version of that file, or else your modifications will be lost.

In general, the following files have to be updated:

File Location Description

embOS libraries Start\Lib embOS object code libraries

RTOS.h Start\Inc embOS header file

OS_Config.h Start\Inc embOS config header file

BSP.h Start\Inc Board support header file

RTOSInit.c Start\BoardSupport\…\Setup Hardware related routines

OS_Error.c Start\BoardSupport\…\Setup embOS error routines

Additional files Start\BoardSupport\…\Setup CPU and compiler-specific files

29.2.1 My project does not work anymore. What did I do

wrong?

One common mistake is to only update the embOS library but not RTOS.h. You should

always ensure the embOS library and RTOS.h belong to the same embOS port version. Also,

please ensure further embOS files like OS_Error.c and RTOSInit.c have been updated to

the same version. If you are still experiencing problems, please do not hesitate to contact

the embOS support (see Contacting support on page 496).

487 CHAPTER 29 embOS API Migration guide

29.3 embOS API Migration guide

Most embOS API names and some object type names have changed between embOS V4

and V5. The legacy embOS API names can still be used and there is no need to update

the user application. embOS is still 100% compatible. However, for new projects the V5

API should be used.

If you want to replace the V4 with the V5 API in an existing application you can easily replace

all API calls. SEGGER provides a CSV file on request which can be used to automatically

replace all API calls.

Please be aware with some API the parameter order has changed. This needs to be adapted

manually.

OS_TASK_CREATE()/ OS_TASK_CREATEEX(): The order of the parameters Priority and

pRoutine has changed.

OS_TASKEVENT_Set(): The order of the parameters pTask and Event has changed.

OS_MEMPOOL_Alloc()/ OS_MEMPOOL_AllocBlocked()/ OS_MEMPOOL_AllocTimed(): The

parameter Purpose does not longer exist.

V4 V5

OS_IsRunning() OS_IsRunning()

OS_Config_Stop() OS_ConfigStop()

OS_InitKern() OS_Init()

OS_IsRunning() OS_IsRunning()

OS_Start() OS_Start()

OS_Stop() OS_Stop()

OS_AddExtendTaskContext() OS_TASK_AddContextExtension()

OS_AddTerminateHook() OS_TASK_AddTerminateHook()

OS_CREATETASK() OS_TASK_CREATE()

OS_CreateTask() OS_TASK_Create()

OS_CREATETASK_EX() OS_TASK_CREATEEX()

OS_CreateTaskEx() OS_TASK_CreateEx()

OS_Delay() OS_TASK_Delay()

OS_DelayUntil() OS_TASK_DelayUntil()

OS_Delayus() OS_TASK_Delayus()

OS_ExtendTaskContext() OS_TASK_SetContextExtension()

OS_GetNumTasks() OS_TASK_GetNumTasks()

OS_GetPriority() OS_TASK_GetPriority()

OS_GetSuspendCnt() OS_TASK_GetSuspendCnt()

OS_GetTaskID() OS_TASK_GetID()

OS_GetTaskName() OS_TASK_GetName()

OS_GetTimeSliceRem() OS_TASK_GetTimeSliceRem()

OS_IsTask() OS_TASK_IsTask()

OS_RemoveTerminateHook() OS_TASK_RemoveTerminateHook()

OS_RemoveAllTerminateHooks() OS_TASK_RemoveAllTerminateHooks()

OS_Resume() OS_TASK_Resume()

OS_ResumeAllTasks() OS_TASK_ResumeAll()

OS_SetDefaultTaskContextExtension() OS_TASK_SetDefaultContextExtension()

OS_SetDefaultTaskStartHook() OS_TASK_SetDefaultStartHook()

OS_SetInitialSuspendCnt() OS_TASK_SetInitialSuspendCnt()

488 CHAPTER 29 embOS API Migration guide

V4 V5

OS_SetPriority() OS_TASK_SetPriority()

OS_SetTaskName() OS_TASK_SetName()

OS_SetTimeSlice() OS_TASK_SetTimeSlice()

OS_Suspend() OS_TASK_Suspend()

OS_SuspendAllTasks() OS_TASK_SuspendAll()

OS_TaskIndex2Ptr() OS_TASK_Index2Ptr()

OS_TerminateTask() OS_TASK_Terminate()

OS_WakeTask() OS_TASK_Wake()

OS_Yield() OS_TASK_Yield()

OS_CREATETIMER() OS_TIMER_CREATE()

OS_CreateTimer() OS_TIMER_Create()

OS_CREATETIMER_EX() OS_TIMER_CREATEEX()

OS_CreateTimerEx() OS_TIMER_CreateEx()

OS_DeleteTimer() OS_TIMER_Delete()

OS_DeleteTimerEx() OS_TIMER_DeleteEx()

OS_GetpCurrentTimer() OS_TIMER_GetCurrent()

OS_GetpCurrentTimerEx() OS_TIMER_GetCurrentEx()

OS_GetTimerPeriod() OS_TIMER_GetPeriod()

OS_GetTimerPeriodEx() OS_TIMER_GetPeriodEx()

OS_GetTimerStatus() OS_TIMER_GetStatus()

OS_GetTimerStatusEx() OS_TIMER_GetStatusEx()

OS_GetTimerValue() OS_TIMER_GetRemainingPeriod()

OS_GetTimerValueEx() OS_TIMER_GetRemainingPeriodEx()

OS_RetriggerTimer() OS_TIMER_Restart()

OS_RetriggerTimerEx() OS_TIMER_RestartEx()

OS_SetTimerPeriod() OS_TIMER_SetPeriod()

OS_SetTimerPeriodEx() OS_TIMER_SetPeriodEx()

OS_StartTimer() OS_TIMER_Start()

OS_StartTimerEx() OS_TIMER_StartEx()

OS_StopTimer() OS_TIMER_Stop()

OS_StopTimerEx() OS_TIMER_StopEx()

OS_TriggerTimer() OS_TIMER_Trigger()

OS_TriggerTimerEx() OS_TIMER_TriggerEx()

OS_ClearEvents() OS_TASKEVENT_Clear()

OS_ClearEventsEx() OS_TASKEVENT_ClearEx()

OS_GetEventsOccurred() OS_TASKEVENT_Get()

OS_SignalEvent() OS_TASKEVENT_Set()

OS_WaitEvent() OS_TASKEVENT_GetBlocked()

OS_WaitEventTimed() OS_TASKEVENT_GetTimed()

OS_WaitSingleEvent() OS_TASKEVENT_GetSingleBlocked()

OS_WaitSingleEventTimed() OS_TASKEVENT_GetSingleTimed()

OS_EVENT_Create() OS_EVENT_Create()

OS_EVENT_CreateEx() OS_EVENT_CreateEx()

489 CHAPTER 29 embOS API Migration guide

V4 V5

OS_EVENT_Delete() OS_EVENT_Delete()

OS_EVENT_Get() OS_EVENT_Get()

OS_EVENT_GetMask() OS_EVENT_GetMask()

OS_EVENT_GetMaskMode() OS_EVENT_GetMaskMode()

OS_EVENT_GetResetMode() OS_EVENT_GetResetMode()

OS_EVENT_Pulse() OS_EVENT_Pulse()

OS_EVENT_Reset() OS_EVENT_Reset()

OS_EVENT_Set() OS_EVENT_Set()

OS_EVENT_SetMask() OS_EVENT_SetMask()

OS_EVENT_SetMaskMode() OS_EVENT_SetMaskMode()

OS_EVENT_SetResetMode() OS_EVENT_SetResetMode()

OS_EVENT_Wait() OS_EVENT_GetBlocked()

OS_EVENT_WaitMask() OS_EVENT_GetMaskBlocked()

OS_EVENT_WaitMaskTimed() OS_EVENT_GetMaskTimed()

OS_EVENT_WaitTimed() OS_EVENT_GetTimed()

OS_CreateRSema() OS_MUTEX_Create()

OS_CREATERSEMA() OS_MUTEX_CREATE()

OS_DeleteRSema() OS_MUTEX_Delete()

OS_GetResourceOwner() OS_MUTEX_GetOwner()

OS_GetSemaValue() OS_MUTEX_GetValue()

OS_Request() OS_MUTEX_Lock()

OS_Unuse() OS_MUTEX_Unlock()

OS_Use() OS_MUTEX_LockBlocked()

OS_UseTimed() OS_MUTEX_LockTimed()

OS_CREATECSEMA() OS_SEMAPHORE_CREATE()

OS_CreateCSema() OS_SEMAPHORE_Create()

OS_CSemaRequest() OS_SEMAPHORE_Take()

OS_DeleteCSema() OS_SEMAPHORE_Delete()

OS_GetCSemaValue() OS_SEMAPHORE_GetValue()

OS_SetCSemaValue() OS_SEMAPHORE_SetValue()

OS_SignalCSema() OS_SEMAPHORE_Give()

OS_SignalCSemaMax() OS_SEMAPHORE_GiveMax()

OS_WaitCSema() OS_SEMAPHORE_TakeBlocked()

OS_WaitCSemaTimed() OS_SEMAPHORE_TakeTimed()

OS_ClearMB() OS_MAILBOX_Clear()

OS_CreateMB() OS_MAILBOX_Create()

OS_DeleteMB() OS_MAILBOX_Delete()

OS_GetMail() OS_MAILBOX_GetBlocked()

OS_GetMail1() OS_MAILBOX_GetBlocked1()

OS_GetMailCond() OS_MAILBOX_Get()

OS_GetMailCond1() OS_MAILBOX_Get1()

OS_GetMailTimed() OS_MAILBOX_GetTimed()

OS_GetMailTimed1() OS_MAILBOX_GetTimed1()

490 CHAPTER 29 embOS API Migration guide

V4 V5

OS_GetMessageCnt() OS_MAILBOX_GetMessageCnt()

OS_Mail_GetPtr() OS_MAILBOX_GetPtrBlocked()

OS_Mail_GetPtrCond() OS_MAILBOX_GetPtr()

OS_Mail_Purge() OS_MAILBOX_Purge()

OS_PeekMail() OS_MAILBOX_Peek()

OS_PutMail() OS_MAILBOX_PutBlocked()

OS_PutMail1() OS_MAILBOX_PutBlocked1()

OS_PutMailCond() OS_MAILBOX_Put()

OS_PutMailCond1() OS_MAILBOX_Put1()

OS_PutMailFront() OS_MAILBOX_PutFrontBlocked()

OS_PutMailFront1() OS_MAILBOX_PutFrontBlocked1()

OS_PutMailFrontCond() OS_MAILBOX_PutFront()

OS_PutMailFrontCond1() OS_MAILBOX_PutFront1()

OS_PutMailTimed() OS_MAILBOX_PutTimed()

OS_PutMailTimed1() OS_MAILBOX_PutTimed1()

OS_WaitMail() OS_MAILBOX_WaitBlocked()

OS_WaitMailTimed() OS_MAILBOX_WaitTimed()

OS_Q_Clear() OS_QUEUE_Clear()

OS_Q_Create() OS_QUEUE_Create()

OS_Q_Delete() OS_QUEUE_Delete()

OS_Q_GetMessageCnt() OS_QUEUE_GetMessageCnt()

OS_Q_GetMessageSize() OS_QUEUE_GetMessageSize()

OS_Q_GetPtr() OS_QUEUE_GetPtrBlocked()

OS_Q_GetPtrCond() OS_QUEUE_GetPtr()

OS_Q_GetPtrTimed() OS_QUEUE_GetPtrTimed()

OS_Q_IsInUse() OS_QUEUE_IsInUse()

OS_Q_PeekPtr() OS_QUEUE_PeekPtr()

OS_Q_Purge() OS_QUEUE_Purge()

OS_Q_Put() OS_QUEUE_Put()

OS_Q_PutEx() OS_QUEUE_PutEx()

OS_Q_PutBlocked() OS_QUEUE_PutBlocked()

OS_Q_PutBlockedEx() OS_QUEUE_PutBlockedEx()

OS_Q_PutTimed() OS_QUEUE_PutTimed()

OS_Q_PutTimedEx() OS_QUEUE_PutTimedEx()

OS_WD_Add() OS_WD_Add()

OS_WD_Check() OS_WD_Check()

OS_WD_Config() OS_WD_Config()

OS_WD_Remove() OS_WD_Remove()

OS_WD_Trigger() OS_WD_Trigger()

OS_SPINLOCK_Create() OS_SPINLOCK_Create()

OS_SPINLOCK_Lock() OS_SPINLOCK_Lock()

OS_SPINLOCK_Unlock() OS_SPINLOCK_Unlock()

OS_SPINLOCK_SW_Create() OS_SPINLOCK_SW_Create()

491 CHAPTER 29 embOS API Migration guide

V4 V5

OS_SPINLOCK_SW_Lock() OS_SPINLOCK_SW_Lock()

OS_SPINLOCK_SW_Unlock() OS_SPINLOCK_SW_Unlock()

OS_DecRI() OS_INT_DecRI()

OS_DI() OS_INT_Disable()

OS_EI() OS_INT_Enable()

OS_IncDI() OS_INT_IncDI()

OS_INT_PRIO_PRESERVE() OS_INT_Preserve()

OS_INT_PRIO_RESTORE() OS_INT_Restore()

OS_INTERRUPT_MaskGlobal() OS_INT_DisableAll()

OS_INTERRUPT_PreserveAndMaskGlobal() OS_INT_PreserveAndDisableAll()

OS_INTERRUPT_PreserveGlobal() OS_INT_PreserveAll()

OS_INTERRUPT_RestoreGlobal() OS_INT_RestoreAll()

OS_INTERRUPT_UnmaskGlobal() OS_INT_EnableAll()

OS_RestoreI() OS_INT_EnableConditional()

OS_CallISR() OS_INT_Call()

OS_CallNestableISR() OS_INT_CallNestable()

OS_EnterInterrupt() OS_INT_Enter()

OS_EnterNestableInterrupt() OS_INT_EnterNestable()

OS_InInterrupt() OS_INT_InInterrupt()

OS_LeaveInterrupt() OS_INT_Leave()

OS_LeaveNestableInterrupt() OS_INT_LeaveNestable()

OS_EnterIntStack() OS_INT_EnterIntStack()

OS_LeaveIntStack() OS_INT_LeaveIntStack()

OS_SetFastIntPriorityLimit() OS_INT_SetPriorityThreshold()

OS_EnterRegion() OS_TASK_EnterRegion()

OS_LeaveRegion() OS_TASK_LeaveRegion()

OS_GetTime() OS_TIME_GetTicks()

OS_GetTime32() OS_TIME_GetTicks32()

OS_Timing_End() OS_TIME_StopMeasurement()

OS_Timing_GetCycles() OS_TIME_GetResult()

OS_Timing_Start() OS_TIME_StartMeasurement()

OS_Timing_Getus() OS_TIME_GetResultus()

OS_Config_SysTimer() OS_TIME_ConfigSysTimer()

OS_GetTime_us() OS_TIME_Getus()

OS_GetTime_us64() OS_TIME_Getus64()

OS_AdjustTime() OS_TICKLESS_AdjustTime()

OS_GetNumIdleTicks() OS_TICKLESS_GetNumIdleTicks()

OS_StartTicklessMode() OS_TICKLESS_Start()

OS_StopTicklessMode() OS_TICKLESS_Stop()

OS_POWER_GetMask() OS_POWER_GetMask()

OS_POWER_UsageDec() OS_POWER_UsageDec()

OS_POWER_UsageInc() OS_POWER_UsageInc()

OS_free() OS_HEAP_free()

492 CHAPTER 29 embOS API Migration guide

V4 V5

OS_malloc() OS_HEAP_malloc()

OS_realloc() OS_HEAP_realloc()

OS_MEMF_Alloc() OS_MEMPOOL_AllocBlocked()

OS_MEMF_AllocTimed() OS_MEMPOOL_AllocTimed()

OS_MEMF_Create() OS_MEMPOOL_Create()

OS_MEMF_Delete() OS_MEMPOOL_Delete()

OS_MEMF_FreeBlock() OS_MEMPOOL_Free()

OS_MEMF_GetBlockSize() OS_MEMPOOL_GetBlockSize()

OS_MEMF_GetMaxUsed() OS_MEMPOOL_GetMaxUsed()

OS_MEMF_GetNumBlocks() OS_MEMPOOL_GetNumBlocks()

OS_MEMF_GetNumFreeBlocks() OS_MEMPOOL_GetNumFreeBlocks()

OS_MEMF_IsInPool() OS_MEMPOOL_IsInPool()

OS_MEMF_Release() OS_MEMPOOL_FreeEx()

OS_MEMF_Request() OS_MEMPOOL_Alloc()

OS_TICK_Config() OS_TICK_Config()

OS_TICK_Handle() OS_TICK_Handle()

OS_TICK_HandleEx() OS_TICK_HandleEx()

OS_TICK_HandleNoHook() OS_TICK_HandleNoHook()

OS_TICK_AddHook() OS_TICK_AddHook()

OS_TICK_RemoveHook() OS_TICK_RemoveHook()

OS_SetObjName() OS_DEBUG_SetObjName()

OS_GetObjName() OS_DEBUG_GetObjName()

OS_AddLoadMeasurement() OS_STAT_AddLoadMeasurement()

OS_GetLoadMeasurement() OS_STAT_GetLoadMeasurement()

OS_STAT_Disable() OS_STAT_Disable()

OS_STAT_Enable() OS_STAT_Enable()

OS_STAT_GetLoad() OS_STAT_GetLoad()

OS_STAT_GetTaskExecTime() OS_STAT_GetExecTime()

OS_STAT_Sample() OS_STAT_Sample()

OS_SendString() OS_COM_SendString()

OS_SetRxCallback() OS_COM_SetRxCallback()

OS_TraceDisable() OS_TRACE_Disable()

OS_TraceDisableAll() OS_TRACE_DisableAll()

OS_TraceDisableFilterId() OS_TRACE_DisableFilterId()

OS_TraceDisableId() OS_TRACE_DisableId()

OS_TraceEnable() OS_TRACE_Enable()

OS_TraceEnableAll() OS_TRACE_EnableAll()

OS_TraceEnableFilterId() OS_TRACE_EnableFilterId()

OS_TraceEnableId() OS_TRACE_EnableId()

OS_TraceData() OS_TRACE_Data()

OS_TraceDataPtr() OS_TRACE_DataPtr()

OS_TracePtr() OS_TRACE_Ptr()

OS_TraceU32Ptr() OS_TRACE_U32Ptr()

493 CHAPTER 29 embOS API Migration guide

V4 V5

OS_TraceVoid() OS_TRACE_Void()

OS_SetTraceAPI() OS_TRACE_SetAPI()

OS_MPU_AddRegion() OS_MPU_AddRegion()

OS_MPU_CallDeviceDriver() OS_MPU_CallDeviceDriver()

OS_MPU_ConfigMem() OS_MPU_ConfigMem()

OS_MPU_Enable() OS_MPU_Enable()

OS_MPU_EnableEx() OS_MPU_EnableEx()

OS_MPU_ExtendTaskContext() OS_MPU_ExtendTaskContext()

OS_MPU_GetThreadState() OS_MPU_GetThreadState()

OS_MPU_SetAllowedObjects() OS_MPU_SetAllowedObjects()

OS_MPU_SetDeviceDriverList() OS_MPU_SetDeviceDriverList()

OS_MPU_SetErrorCallback() OS_MPU_SetErrorCallback()

OS_MPU_SwitchToUnprivState() OS_MPU_SwitchToUnprivState()

OS_MPU_SwitchToUnprivStateEx() OS_MPU_SwitchToUnprivStateEx()

OS_MPU_AddSanityCheckBuffer() OS_MPU_SetSanityCheckBuffer()

OS_MPU_SanityCheck() OS_MPU_SanityCheck()

OS_GetIntStackBase() OS_STACK_GetIntStackBase()

OS_GetIntStackSize() OS_STACK_GetIntStackSize()

OS_GetIntStackSpace() OS_STACK_GetIntStackSpace()

OS_GetIntStackUsed() OS_STACK_GetIntStackUsed()

OS_GetStackBase() OS_STACK_GetTaskStackBase()

OS_GetStackSize() OS_STACK_GetTaskStackSize()

OS_GetStackSpace() OS_STACK_GetTaskStackSpace()

OS_GetStackUsed() OS_STACK_GetTaskStackUsed()

OS_GetSysStackBase() OS_STACK_GetSysStackBase()

OS_GetSysStackSize() OS_STACK_GetSysStackSize()

OS_GetSysStackSpace() OS_STACK_GetSysStackSpace()

OS_GetSysStackUsed() OS_STACK_GetSysStackUsed()

OS_SetStackCheckLimit() OS_STACK_SetCheckLimit()

OS_GetStackCheckLimit() OS_STACK_GetCheckLimit()

OS_OnRx() OS_COM_OnRx()

OS_OnTx() OS_COM_OnTx()

OS_EvaPacketEx() OS_COM_EvaPacketEx()

OS_GetCPU() OS_INFO_GetCPU()

OS_GetLibMode() OS_INFO_GetLibMode()

OS_GetLibName() OS_INFO_GetLibName()

OS_GetModel() OS_INFO_GetModel()

OS_GetVersion() OS_INFO_GetVersion()

Changed object types:

V4 V5

OS_RSEMA OS_MUTEX

OS_CSEMA OS_SEMAPHORE

494 CHAPTER 29 embOS API Migration guide

V4 V5

OS_Q OS_QUEUE

OS_Q_SRCLIST OS_QUEUE_SRCLIST

OS_MEMF OS_MEMPOOL

OS_TASK_EVENT OS_TASKEVENT

Chapter 30

Support

496 CHAPTER 30 Contacting support

30.1 Contacting support

This chapter should help if any problem occurs and describes how to contact the embOS

support.

If you are a registered embOS user and you need to contact the embOS support please

send the following information via email to support_embos@segger.com:

• Which embOS do you use? (CPU, compiler).

• The embOS version.

• Your embOS registration number.

• If you are unsure about the above information you can also use the name of the embOS

zip file (which contains the above information).

• A detailed description of the problem.

• Optionally a project with which we can reproduce the problem.

Note

Even without a valid license, feel free to contact our support e.g. in case of questions

during your evaluation of embOS or for hobbyist purposes.

Please also take a few moments to help us improve our services by providing a short

feedback once your support case has been solved.

Chapter 31

Performance and Resource

Usage

498 CHAPTER 31 Introduction

31.1 Introduction

This chapter covers the performance and resource usage of embOS. It explains how to

benchmark embOS and contains information about the memory requirements in typical

systems which can be used to obtain sufficient estimates for most target systems.

High performance combined with low resource usage has always been a major design con-

sideration. embOS runs on 8/16/32 bit CPUs. Depending on which features are being used,

even single-chip systems with less than 2 Kbytes ROM and 1 Kbyte RAM can be supported

by embOS. The actual performance and resource usage depends on many factors (CPU,

compiler, memory model, optimization, configuration, etc.).

499 CHAPTER 31 Memory requirements

31.2 Memory requirements

The memory requirements of embOS (RAM and ROM) differs depending on the used fea-

tures of the library. The following table shows the memory requirements for the different

modules. These values are typical values for a 32 bit CPU and depend on CPU, compiler,

and library model used.

Module Memory type Memory requirements

embOS kernel ROM 1700 bytes

embOS kernel RAM 71 bytes

Mailbox RAM 24 bytes

Semaphore RAM 8 bytes

Mutex RAM 16 bytes

Software timer RAM 20 bytes

Task event RAM 0 bytes

500 CHAPTER 31 Performance

31.3 Performance

The following section shows how to benchmark embOS with the supplied example pro-

grams.

31.4 Benchmarking

embOS is designed to perform fast context switches. This section describes two different

methods to calculate the execution time of a context switch from a task with lower priority

to a task with a higher priority.

The first method uses port pins and requires an oscilloscope. The second method uses the

high-resolution measurement functions. Example programs for both methods are supplied

in the \Application directory of your embOS shipment.

SEGGER uses these programs to benchmark embOS performance. You can use these exam-

ples to evaluate the benchmark results. Note that the actual performance depends on many

factors (CPU, clock speed, toolchain, memory model, optimization, configuration, etc.).

Please be aware that the number of cycles are not equal to the number of instructions.

Many instructions on ARM need two or three cycles even at zero wait-states, e.g. LDR needs

3 cycles.

The following table gives an overview about the variations of the context switch time de-

pending on the memory type and the CPU mode:

Target Memory Time / Cycles

ST STM32F756 @ 200 MHz RAM 1.5us / 260

Renesas RZ @ 400 MHz RAM 720ns / 287

All named example performance values in the following section are determined with the

following system configuration:

All sources are compiled with IAR Embedded Workbench version 6.40.5, OS_LIBMODE_XR

and high optimization level. embOS version 4.14 has been used; values may differ for

different builds.

501 CHAPTER 31 Benchmarking

31.4.1 Measurement with port pins and oscilloscope

The example file OS_MeasureCST_Scope.c uses the BSP.c module to set and clear a port

pin. This allows measuring the context switch time with an oscilloscope. The following source

code is an excerpt from OS_MeasureCST_Scope.c:

#include "RTOS.h"

#include "BSP.h"

static OS_STACKPTR int StackHP[128], StackLP[128]; /* Task stacks */

static OS_TASK TCBHP, TCBLP; /* Task-control-blocks */

/*********************************************************************

* HPTask

static void HPTask(void) {

while (1) {

OS_TASK_Suspend(NULL); // Suspend high priority task

BSP_ClrLED(0); // Stop measurement

}

/*********************************************************************

* LPTask

static void LPTask(void) {

while (1) {

OS_TASK_Delay(100); // Synchronize to tick to avoid jitter

// Display measurement overhead

BSP_SetLED(0);

BSP_ClrLED(0);

// Perform measurement

BSP_SetLED(0); // Start measurement

OS_TASK_Resume(&TCBHP); // Resume high priority task to force task switch

}

/*********************************************************************

* main

int main(void) {

OS_Init(); // Initialize embOS

OS_InitHW(); // Initialize hardware for embOS

BSP_Init(); // Initialize LED ports

OS_TASK_CREATE(&TCBHP, "HP Task", 100, HPTask, StackHP);

OS_TASK_CREATE(&TCBLP, "LP Task", 50, LPTask, StackLP);

OS_Start(); // Start multitasking

return 0;

}

502 CHAPTER 31 Benchmarking

31.4.1.1 Oscilloscope analysis

The context switch time is the time between switching the LED on and off. If the LED is

switched on with an active high signal, the context switch time is the time between the

rising and the falling edge of the signal. If the LED is switched on with an active low signal,

the signal polarity is reversed.

The real context switch time is shorter, because the signal also contains the overhead of

switching the LED on and off. The time of this overhead is also displayed on the oscilloscope

as a small peak right before the task switch time display and must be subtracted from

the displayed context switch time. The picture below shows a simplified oscilloscope signal

with an active-low LED signal (low means LED is illuminated). There are switching points

to determine:

• A = LED is switched on for overhead measurement

• B = LED is switched off for overhead measurement

• C = LED is switched on right before context switch in low-prio task

• D = LED is switched off right after context switch in high-prio task

The time needed to switch the LED on and off in subroutines is marked as time tAB. The

time needed for a complete context switch including the time needed to switch the LED on

and off in subroutines is marked as time tCD.

The context switching time tCS is calculated as follows:

tCS = tCD - tAB

503 CHAPTER 31 Benchmarking

31.4.1.2 Example measurements Renesas RZ, Thumb2 code in RAM

Task switching time has been measured with the parameters listed below:

embOS Version V4.14

Application program: OS_MeasureCST_Scope.c

Hardware: Renesas RZ processor with 399MHz

Program is executing in RAM

Thumb2 mode is used

Compiler used: SEGGER Embedded Studio V2.10B (GCC)

CPU frequency (fCPU): 399.0MHz

CPU clock cycle (tCycle): tCycle = 1 / fCPU = 1 / 399.0MHz = 2.506ns

Measuring tAB and tCD

tAB is measured as 480ns.

The number of cycles

calculates as follows:

CyclesAB = tAB / tCycle

= 480ns / 2.506ns

= 191.54 Cycles

=> 192 Cycles

tCD is measured as 12000ns.

The number of cycles

calculates as follows:

CyclesCD = tCD / tCycle

= 1200ns / 2.506ns

= 478.85 Cycles

=> 479 Cycles

Resulting context switching time and number of cycles

The time which is required for the pure context switch is:

tCS = tCD - tAB = 479 Cycles - 192 Cycles = 287 Cycles

=> 287 Cycles (0.72us @399 MHz).

504 CHAPTER 31 Benchmarking

31.4.1.3 Measurement with high-resolution timer

The context switch time may be measured with the high-resolution timer. Refer to section

High-resolution measurement on page 289 for detailed information about the embOS high-

resolution measurement.

The example OS_MeasureCST_HRTimer_embOSView.c uses a high resolution timer to mea-

sure the context switch time from a low priority task to a high priority task and displays

the results on embOSView.

#include "RTOS.h"

#include <stdio.h>

static OS_STACKPTR int StackHP[128], StackLP[128]; // Task stacks

static OS_TASK TCBHP, TCBLP; // Task-control-blocks

static OS_U32 Time; // Timer values

/*********************************************************************

* HPTask

static void HPTask(void) {

while (1) {

OS_TASK_Suspend(NULL); // Suspend high priority task

OS_TIME_StopMeasurement(&_Time); // Stop measurement

}

/*********************************************************************

* LPTask

static void LPTask(void) {

char acBuffer[100]; // Output buffer

OS_U32 MeasureOverhead; // Time for Measure Overhead

OS_U32 v;

// Measure Overhead for time measurement so we can take

// this into account by subtracting it

OS_TIME_StartMeasurement(&MeasureOverhead);

OS_TIME_StopMeasurement(&MeasureOverhead);

// Perform measurements in endless loop

while (1) {

OS_TASK_Delay(100); // Sync. to tick to avoid jitter

OS_TIME_StartMeasurement(&_Time); // Start measurement

OS_TASK_Resume(&TCBHP);

// Resume high priority task to force task switch

v = OS_TIME_GetResult(&_Time);

v -= OS_TIME_GetResult(&MeasureOverhead);

v = OS_ConvertCycles2us(1000 * v); // Convert cycles to nano-seconds

sprintf(acBuffer, "Context switch time: %1u.%.31u usec\r",

v / 1000uL, v % 1000uL);

OS_COM_SendString(acBuffer);

}

The example program calculates and subtracts the measurement overhead. The results will

be transmitted to embOSView, so the example runs on every target that supports UART

communication to embOSView.

The example program OS_MeasureCST_HRTimer_Printf.c is identical to the example pro-

gram OS_MeasureCST_HRTimer_embOSView.c but displays the results with the printf()

function for those debuggers which support terminal output emulation.

Chapter 32

Glossary

506 CHAPTER 32

Term Definition

Cooperative multitasking

A scheduling system in which each task is allowed to

run until it gives up the CPU; an ISR can make a higher

priority task ready, but the interrupted task will be re-

turned to and finished first.

Counting semaphore

A type of semaphore that keeps track of multiple re-

sources. Used when a task must wait for something that

can be signaled more than once.

CPU Central Processing Unit. The “brain” of a microcontroller;

the part of a processor that carries out instructions.

Critical region A section of code which must be executed without inter-

ruption.

Event A message sent to a single, specified task that some-

thing has occurred. The task then becomes ready.

Interrupt Handler

Interrupt Service Routine. The routine is called by the

processor when an interrupt is acknowledged. ISRs

must preserve the entire context of a task (all regis-

ters).

ISR

Interrupt Service Routine. The routine is called by the

processor when an interrupt is acknowledged. ISRs

must preserve the entire context of a task (all regis-

ters).

Mailbox A data buffer managed by an RTOS, used for sending

messages to a task or interrupt handler.

Message An item of data (sent to a mailbox, queue, or other con-

tainer for data).

Multitasking

The execution of multiple software routines indepen-

dently of one another. The OS divides the processor’s

time so that the different routines (tasks) appear to be

happening simultaneously.

Mutex

A data structure used for managing resources by en-

suring that only one task has access to a resource at a

time.

NMI

Non-Maskable Interrupt. An interrupt that cannot be

masked (disabled) by software. Example: Watchdog

timer interrupt.

Preemptive multitasking

A scheduling system in which the highest priority task

that is ready will always be executed. If an ISR makes a

higher priority task ready, that task will be executed be-

fore the interrupted task is returned to.

Process

Processes are tasks with their own memory layout. Two

processes cannot normally access the same memory lo-

cations. Different processes typically have different ac-

cess rights and (in case of MMUs) different translation

tables.

Processor Short for microprocessor. The CPU core of a controller.

Priority The relative importance of one task to another. Every

task in an RTOS has a priority.

Priority inversion

A situation in which a high priority task is delayed while

it waits for access to a shared resource which is in use

by a lower priority task. A task with medium priority

in the ready state may run, instead of the high priori-

ty task. embOS avoids this situation by priority inheri-

tance.

507 CHAPTER 32

Term Definition

Queue

Like a mailbox, but used for sending larger messages,

or messages of individual size, to a task or an interrupt

handler.

Ready Any task that is in “ready state” will be activated when

no other task with higher priority is in “ready state”.

Resource

Anything in the computer system with limited availabili-

ty (for example memory, timers, computation time). Es-

sentially, anything used by a task.

RTOS Real-time Operating System.

Running task Only one task can execute at any given time. The task

that is currently executing is called the running task.

Scheduler

The program section of an RTOS that selects the active

task, based on which tasks are ready to run, their rela-

tive priorities, and the scheduling system being used.

Semaphore A data structure used for synchronizing tasks.

Software timer A data structure which calls a user-specified routine af-

ter a specified delay.

Stack

An area of memory with LIFO storage of parameters,

automatic variables, return addresses, and other in-

formation that needs to be maintained across function

calls. In multitasking systems, each task normally has

its own stack.

Superloop

A program that runs in an infinite loop and uses no re-

al-time kernel. ISRs are used for real-time parts of the

software.

Task

A program running on a processor. A multitasking sys-

tem allows multiple tasks to execute independently from

one another.

Thread

Threads are tasks which share the same memory layout.

Two threads can access the same memory locations.

If virtual memory is used, the same virtual to physi-

cal translation and access rights are used(c.f. Thread,

Process)

Tick The OS timer interrupt. Typically equals 1 msec.

Time slice The time (number of system ticks) for which a task will

be executed until a round-robin task change may occur.

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