TDGL005 - MICROCHIP - Datasheet.Live

™

Revision: July 16, 2011

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Overview

The chipKIT Basic I/O Shield is a input/output

expansion board designed for use with chipKIT

microcontroller boards such as the Uno32™

and the Max32™.

The Basic I/O Shield is designed to provide a

range of input/output devices suitable for

beginners learning about microcontrollers and

various types of I/O devices, or for use by

more advanced user to provide inputs or

outputs for their own projects.

The Basic I/O Shield provides simple digital

input devices such as switches and buttons,

and digital output devices such as discrete

LEDs and high current open FET drivers. It

provides more advanced devices such as an

C EEPROM, an I

C temperature sensor, and

organic LED graphic display. A potentiometer

is also provided for use as an analog input

device.

The Basic I/O Shield is designed to the same

form factor as the Uno32 board, but is also

useable with the Max32 board.

Features:

128x32 pixel OLED graphic display

C temperature sensor

256Kbit I

C EEPROM

C daisy chain connector

4 push buttons

4 slide switches

8 discrete LEDs

4 open drain FET drivers

Analog potentiometer

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 2 of 15

chipKIT Basic I/O Shield Hardware Overview

The Basic I/O Shield has the following hardware features:

1) Push Buttons

Four push buttons provide momentary contact discrete digital inputs. These can be

accessed using the digitalRead function.

2) Slide switches

Four slide switches that provide discrete digital inputs. These can be accessed using the

digitalRead function.

3) J2 – Shield Power Connector

This connector powers the board, receiving power from the chipKIT microcontroller board.

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 3 of 15

4) J3 – Analog Signal Connector

Pin 1 (analog signal A0) is connected to a potentiometer. Pins 5 and 6 (labeled as A4 and

A5) provide access to the I

C signals SDA and SCL for the I

C bus. The I

C bus is used to

access the temperature sensor and the EEPROM and for the I

C daisy chain connector.

Note: On the Uno32 it is necessary to set jumpers JP6 & JP7 to the correct position for

accessing the I

C signals on that board. On the Max32 board, it is necessary to use jumper

wires to bring the I

C signals onto the board, as the connector providing the I

C bus on the

Max32 board doesn’t contact the Basic I/O Shield.

5) Discrete LEDs

Eight LEDs that provide discrete digital outputs. These can be accessed individually using

the digitalWrite function. The LEDs are connected to the low eight bits of microcontroller

PORTE and all eight can be written at the same time by writing to PORTE.

6) IC2 – Temperature Sensor

This is a Microchip TCN75A digital temperature sensor. It is accessed via the I

C bus.

7) JP2/JP3 – I

C Pull-up Resistor Enable Jumpers

These jumpers are used to enable or disable the presence of the I

C pull-up resistors on

the I

C bus. Having the shorting blocks installed enables the resistors. Removing the

shorting blocks disables them.

8) J11 – I

C Daisy Chain Connector

This is a 2x4 pin header connector that provides access to the I

C signals SDA and SCL

as well as power from the 3.3V power bus and ground. This can be used to extend the I

bus off of the board and to power external I

C device. Digilent has cables and a selection

of I

C peripheral modules that can be accessed using this connector.

9) Potentiometer

This is a 10K ohm potentiometer connected across VCC3V3 and ground. It provides an

analog input voltage to analog input A0.

10) J1 and J2 – Digital Signal Connectors

These connectors bring digital signals from the chipKIT microcontroller board onto the

Basic I/O Shield board.

11) Organic LED Graphic Display

This is a 128x32 pixel monochrome OLED graphic display panel. This display panel is

accessed using the SPI interface.

12) J9 & J10 – Digital I/O Signal Connectors

These are screw terminal connectors that provide access to digital I/O signals 3, 5, 6, and

9. These are four of the PWM signals from the chipKIT microcontroller board.

13) J6 – Open Drain FET Power Connector

This provides access to the power connections for the open drain FETs.

14) , J7, & J8 – Open Drain FET Output

These provide access to the outputs of the open drain FETs.

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 4 of 15

chipKIT Basic I/O Shield Hardware Description

Introduction

The following gives a basic description of the

input/output hardware contained in the Basic

I/O Shield and how to use it. Refer to Appendix

A for a table showing pin definitions, and

Appendix B for example code to use the OLED

graphic display.

OLED Graphic Display

The Basic I/O board provides a 128x32 pixel,

Organic LED (OLED), graphic display panel.

The graphic display panel used is the

WiseChip/Univision UG-23832HSWEG04. This

display uses the Soloman Systech SSD1306

display controller.

The UG2832 has a power on/power off

sequence that should be followed. Failure to

follow the power on/power off sequence can

shorten the life of the display. The Basic I/O

provides two FETs for software control of the

two power supplies for the display. The

VDD_EN control is used to turn on/off the

power to the logic of the display. The

VBAT_EN control is used to turn on/off power

to the OLED display itself. These two pins

have pull-up resistors to turn off their

respective power supplies when not being

driven. The pin is made an output and driven

low to turn on the power supply.

Power on sequence:

Apply power to VDD

Send Display Off command

Initialize display to desired operating mode

Clear screen

Apply power to VBAT

Delay 100ms

Send Display On command

Power off sequence:

Send Display Off command

Power off VBAT

Delay 100ms

Power off VDD

The display has a D/C pin (display or

command select) that is used to determine

whether bytes sent to the display are

interpreted as commands or as display data.

The D/C pin is set HIGH for display buffer

access and LOW for command access.

The RES pin is used to reset the SG1306

display controller. The RES pin is driven LOW

for reset and driven HIGH for normal operation.

The low going reset pulse must be a minimum

of 3us (microseconds) for the display controller

to reset correctly.

The UG2832 is a serial device that is accessed

using SPI. It is however, a write-only device. It

is not possible to read back either the display

buffer contents or any kind of status from the

panel. The maximum SPI clock frequency

supported by the UG2832 is 10Mhz. Due to pin

limitations between the Basic I/O and the

Uno32 board, the select pin (SS) is wired low

on the Basic I/O board and the display is

always enabled to receive data over the SPI

interface.

Digilent has a library for use with the Basic I/O

that provides functions for initializing the

display and rendering simple text and graphics

onto the display. This library can be used as-is

or as a starting point for a more sophisticated

graphics library. This library is available on the

Digilent web site and in the third part libraries

repository on github.

Appendix B provides example code that shows

initializing the display and writing to it.

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 5 of 15

Discrete Digital I/O Devices

The Basic I/O Shield provides various discrete

digital I/O devices. These can be accessed

using the digitalRead and digitalWrite

functions. The pinMode function is used to set

the pin to input or output.

When the buttons and switches on the Basic

I/O are not being used, the pins are available

on the pass-through shield connectors for use

by other shields in the stack. The pins used by

the LEDs are also available, however the

presence of the LEDs on the lines will load

them down, possibly causing some devices to

not work. It is safe to use any of these pins as

either inputs or outputs.

Push Buttons: There are four push buttons

switches labeled BTN1 (pin 4), BTN2 (pin 34),

BTN3 (pin 36), and BTN4 (pin 37). The

digitalRead function will return LOW if the

button is not pressed and HIGH when the

button is pressed.

Slide Switches: There are four slide switches

labeled SW1 (pin 2), SW2 (pin 7), SW3 (pin 8)

and SW4 (pin 35). The digitalRead function will

return LOW when the switch is down (toward

the push buttons) and HIGH when the switch is

up (toward the OLED display).

LEDs: There are eight LEDs, labeled LD1 –

LD8 accessed as digital pins 33 – 26. An LED

will be illuminated when the corresponding pin

is set to the HIGH state using the digitalWrite

function and off when set to the LOW state.

The LEDs are attached to the low eight bits of

PORTE, with LD1 connected to PORTE bit 0,

and LD8 connected to PORTE bit 7. An 8-bit

value written to PORTE (or LATE) will display

the corresponding binary value on the LEDs.

Open Drain FET Outputs

The Basic I/O provides four open drain FET

outputs. These are low-side N-channel devices

and can be used to provide a digital switch

closure to ground. These can be used to

switch external loads, such as relay coils,

solenoids, stepper motors, and so on.

The FETs used are the NTHD4508N. These

FETs are rated for a maximum V

(voltage

from drain to source) of 20V. They are rated for

a maximum continuous current of 3.0A at 25ºC

and 2.2A at 85ºC. For more detailed

specifications for the FETs refer to the data

sheet available from the On Semiconductor

web site.

The FETs are labeled Q1A (pin 9), Q1B (pin

6), Q2A (pin 5), and Q2B (pin 3). These four

pins are also four of the PWM outputs

supported by the chipKIT boards and the FETs

can be switched using pulse width modulation

(PWM) using the analogWrite function.

An FET is switched on by driving its gate high.

When the FET is on, it provides a low

impedance path to ground (similar to a closed

switch to ground). When the FET is switched

off by driving its gate low, it becomes a high

impedance path to ground (similar to an open

switch to ground). Pull-down resistors are

connected to the gate of each FET to ensure

that it is off unless being actively driven high by

the microcontroller on the chipKIT board.

The FET outputs are accessed via the screw

terminal connectors J7 and J8 on the left side

of the board. The digital signals used to switch

the FETs on and off are also available on

screw terminal connectors J9 and J10 at the

left side of the upper edge of the board.

A FET is used to switch an external load, such

as a relay coil, on and off. The load is wired

between the positive side of an external power

supply and the output of the FET. When the

FET is switched on, current will flow from the

external power supply through the load and the

FET to ground.

FETs are often used to switch highly inductive

loads, such as relay coils, solenoids, and

motors. When the current through an inductive

load is switched off, a voltage spike will occur

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 6 of 15

that can damage the FET. The Basic I/O

provides clamp diodes (also called snubber or

flyback diodes) to clamp the voltage spike and

feed the current back to the external supply.

Screw terminal connector J6 is used to provide

the power and ground connections back to the

external power supply. The negative (-) pin of

J6 connects the external supply ground with

the Basic I/O ground, and the positive (+)

terminal connects the Basic I/O to the external

supply voltage.

The unloaded two pin header JP1 can be used

to connect the board VCC5V0 power supply

bus to the external power supply bus so that

the board 5V supply can be used instead of an

external supply. In this case, J6 is used to

connect the board supply to the external loads.

If this is done, the total current consumed by all

external loads must not exceed 2A or the

current rating of the board power supply

(whichever is less).

C Bus

The I

C bus from the chipKIT microcontroller

board is brought onto the Basic I/O Shield.

There are two I

C devices on the board and a

connector for taking the I

C bus off of the

board to connect to additional external I

devices.

C Connector: Connector J11 can be used to

extend the I

C bus off of the board to connect

to additional external I

C devices. J11 is a

standard 2x4 pin header connector with 0.100”

spaced pins. It provides access to the I

signals, SCL and SDA, plus VCC3V3 and

ground. The VCC3V3 can be used to power

external I

C devices.

The I

C bus uses open collector drivers to

allow multiple devices to drive the bus signals.

This means that pull-up resistors must be

provided to supply the logic high state for the

signals. The Basic I/O provides 2.2Kohm pull-

up resistors. Generally, only one set of pull-up

resistors are used on the bus. Jumpers JP2

and JP3 can be used to disable the on-board

pull-up resistors if a different value is needed

or some other device on the bus is providing

the pull-ups. The on-board pull-up resistors are

enabled by install shorting blocks on JP2 and

JP3. Removing the shorting blocks disables

the pull-up resistors.

Digilent has several small I/O modules

available that can be connected using the I

connector. These include a 3-axis

accelerometer, 4-channel, 12-bit A/D

converter, serial character LCD panel, 3-axis

gyroscope, real-time clock/calendar, and I/O

expander.

EEPROM: A 256Kbit (32Kbyte), I

C EEPROM

is provided using a Microchip 24LC256. This

EEPROM, IC1, is located on the bottom left of

the board, just below the chipKIT logo.

The seven bit I

C device address for the

EEPROM is ‘1010000’.

Digilent provides a library for accessing this

EEPROM. The library is available on the

Digilent web site and in the third party libraries

repository on github.

For complete technical documentation on the

24LC256, refer to the data sheet available on

the Microchip web site.

Temperature Sensor: A digital temperature

sensor is provided using a Microchip TCN75A

2-Wire Serial Temperature Sensor. The

temperature sensor, IC2, is an I

C device, and

is located in the lower right corner of the board.

The TCN75A is rated for an accuracy of +/-1ºC

and has selectable resolution from 0.5ºC down

to 0.0625ºC. The seven bit device address is

‘1001000’.

Digilent provides a library for accessing the

temperature sensor. This library is available on

the Digilent web site and in the third party

library repository on github.

The TCN75A provides an alert output that can

be programmed for various functions. This

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 7 of 15

output can be accessed using JP4, which is

adjacent to IC2.

For complete technical documentation on the

TCN75A, refer to the data sheet available on

the Microchip web site.

Potentiometer

A potentiometer (pot) is provided on the board

to be used as an analog signal source or

analog control input. The pot is a 10Kohm

trimmer pot connected between the VCC3V3

supply and ground. The wiper of the pot is

connected to analog input A0.

The pot is read using the analogRead function.

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 8 of 15

Appendix A: chipKIT Basic I/O Shield Pinout Table

Uno32

pin #

Max32

pin #

Function

Description

Notes

10 10 RES OLED reset JP4 on Uno32

39 83 DC OLED data/command select

13 13 SCLK OLED serial clock

11 11 SDIN OLED serial data in JP7 on Uno32/JP4 on Max32

40 84 VBAT_EN OLED VBAT enable

38 82 VDD_EN OLED VDD enable

33 77 LD1 User LED

32 76 LD2 User LED

31 75 LD3 User LED

30 74 LD4 User LED

29 73 LD5 User LED

28 72 LD6 User LED

27 71 LD7 User LED

26 70 LD8 User LED

4 4 BTN1 Push button

34 78 BTN2 Push button

36 79 BTN3 Push button

37 80 BTN4 Push button

2 2 SW1 Slide switch

7 7 SW2 Slide switch

8 8 SW3 Slide switch

35 79 SW4 Slide switch

3 3 OC1 Open drain/PWM output

5 5 OC2 Open drain/PWM output

6 6 OC3 Open drain/PWM output

9 9 OC4 Open drain/PWM output

19 59 SCL I2C clock JP8 on Uno32/jumper wire on Max32

18 58 SDA I2c data JP6 on Uno32/jumper wire on Max32

14 54 A0 Potentiometer

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 9 of 15

Appendix B: Example Driver Code

The following gives an example of code to initialize the display controller and write the contents of a

memory buffer into the display. This example is written for the chipKIT Uno32 board.

Symbol and Variable Declarations

/* ------------------------------------------------------------ */

/* Pin definitions for access to OLED control signals on chipKIT Uno32

#define prtVddCtrl IOPORT_F

#define prtVbatCtrl IOPORT_F

#define prtDataCmd IOPORT_F

#define prtReset IOPORT_G

#define bitVddCtrl BIT_6

#define bitVbatCtrl BIT_5

#define bitDataCmd BIT_4

#define bitReset BIT_9

/* ------------------------------------------------------------ */

/* Symbols describing the geometry of the display.

#define cbOledDispMax 512 //max number of bytes in display buffer

#define ccolOledMax 128 //number of display columns

#define crowOledMax 32 //number of display rows

#define cpagOledMax 4 //number of display memory pages

/* ------------------------------------------------------------ */

/* This array is the off-screen frame buffer used for rendering.

** It isn't possible to read back from the OLED display device,

** so display data is rendered into this off-screen buffer and then

** copied to the display.

BYTE rgbOledBmp[cbOledDispMax];

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 10 of 15

PIC32 Hardware Initialization

The following function initializes the PIC32 hardware for talking to the display. It initializes the SPI

controller and sets the control pins to be outputs.

/* ------------------------------------------------------------ */

/*** OledHostInit

** Parameters:

** none

** Return Value:

** none

** Errors:

** none

** Description:

** Perform PIC32 device initialization to prepare for use

** of the OLED display.

** This example is hard coded for the chipKIT Uno32 and

** SPI2.

void

OledHostInit()

{

unsigned int tcfg;

/* Initialize SPI port 2.

SPI2CON = 0;

SPI2BRG = 15; //8Mhz, with 80Mhz PB clock

SPI2STATbits.SPIROV = 0;

SPI2CONbits.CKP = 1;

SPI2CONbits.MSTEN = 1;

SPI2CONbits.ON = 1;

/* Make pins RF4, RF5, and RF6 be outputs.

PORTSetBits(IOPORT_F, bitVddCtrl|bitVbatCtrl|bitDataCmd);

PORTSetPinsDigitalOut(prtDataCmd, bitDataCmd); //Data/Command# select

PORTSetPinsDigitalOut(prtVddCtrl, bitVddCtrl); //VDD power control (1=off)

PORTSetPinsDigitalOut(prtVbatCtrl, bitVbatCtrl); //VBAT power control (1=off)

/* Make the RG9 pin be an output. On the Basic I/O Shield, this pin

** is tied to reset.

PORTSetBits(prtReset, bitReset);

PORTSetPinsDigitalOut(prtReset, bitReset);

}

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 11 of 15

Display Controller Initialization

The following function performs initialization of the display controller on the display panel. This

performs the power up sequence on the display and initializes it for a non-interleaved display buffer

with the origin in the upper left corner.

/* ------------------------------------------------------------ */

/*** OledDspInit

** Parameters:

** none

** Return Value:

** none

** Errors:

** none

** Description:

** Initialize the OLED display controller and turn the display on.

void

OledDspInit()

{

/* We're going to be sending commands, so clear the Data/Cmd bit

PORTClearBits(prtDataCmd, bitDataCmd);

/* Start by turning VDD on and wait a while for the power to come up.

PORTClearBits(prtVddCtrl, bitVddCtrl);

DelayMs(1);

/* Display off command

Spi2PutByte(0xAE);

/* Bring Reset low and then high

PORTClearBits(prtReset, bitReset);

DelayMs(1);

PORTSetBits(prtReset, bitReset);

/* Send the Set Charge Pump and Set Pre-Charge Period commands

Spi2PutByte(0x8D);

Spi2PutByte(0x14);

Spi2PutByte(0xD9);

Spi2PutByte(0xF1);

/* Turn on VCC and wait 100ms

PORTClearBits(prtVbatCtrl, bitVbatCtrl);

DelayMs(100);

/* Send the commands to invert the display. This puts the display origin

** in the upper left corner.

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 12 of 15

Spi2PutByte(0xA1); //remap columns

Spi2PutByte(0xC8); //remap the rows

/* Send the commands to select sequential COM configuration. This makes the

** display memory non-interleaved.

Spi2PutByte(0xDA); //set COM configuration command

Spi2PutByte(0x20); //sequential COM, left/right remap enabled

/* Send Display On command

Spi2PutByte(0xAF);

}

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 13 of 15

Display Memory Update

This function copies the contents of a 512 byte buffer from PIC32 memory to the display. The display

memory is organized as four pages of 128 bytes each. Each memory page corresponds to an eight

pixel high stripe across the display. Each byte in the memory page corresponds to an eight pixel high

column on the display. The least significant bit in a display byte is the top most pixel, and the most

significant bit the bottom most pixel. The first byte in the page corresponds to the left most pixels on

the display and the last byte the right most pixels.

This function assumes that the display buffer to be copied is the global variable

rgbOledBmp

/* ------------------------------------------------------------ */

/*** OledUpdate

** Parameters:

** none

** Return Value:

** none

** Errors:

** none

** Description:

** Update the OLED display with the contents of the memory buffer

void

OledUpdate()

{

int ipag;

int icol;

BYTE * pb;

pb = rgbOledBmp;

for (ipag = 0; ipag < cpagOledMax; ipag++) {

PORTClearBits(prtDataCmd, bitDataCmd);

/* Set the page address

Spi2PutByte(0x22); //Set page command

Spi2PutByte(ipag); //page number

/* Start at the left column

Spi2PutByte(0x00); //set low nybble of column

Spi2PutByte(0x10); //set high nybble of column

PORTSetBits(prtDataCmd, bitDataCmd);

/* Copy this memory page of display data.

OledPutBuffer(ccolOledMax, pb);

pb += ccolOledMax;

}

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 14 of 15

Low Level SPI Functions

The following functions are used to write data to the display panel using the SPI controller.

/* ------------------------------------------------------------ */

/*** OledPutBuffer

** Parameters:

** cb - number of bytes to send/receive

** rgbTx - pointer to the buffer to send

** Return Value:

** none

** Errors:

** none

** Description:

** Send the bytes specified in rgbTx to the slave.

void

OledPutBuffer(int cb, BYTE * rgbTx)

{

int ib;

BYTE bTmp;

/* Write/Read the data

for (ib = 0; ib < cb; ib++) {

/* Wait for transmitter to be ready

while (SPI2STATbits.SPITBE == 0);

/* Write the next transmit byte.

SPI2BUF = *rgbTx++;

/* Wait for receive byte.

while (SPI2STATbits.SPIRBF == 0);

bTmp = SPI2BUF;

}

/* ------------------------------------------------------------ */

/*** Spi2PutByte

** Parameters:

** bVal - byte value to write

** Return Value:

** Returns byte read

** Errors:

** none

** Description:

** Write/Read a byte on SPI port 2

chipKIT Basic I/O Shield Reference Manual

www.digilentinc.com page 15 of 15

BYTE

Spi2PutByte(BYTE bVal)

{

BYTE bRx;

/* Wait for transmitter to be ready

while (SPI2STATbits.SPITBE == 0);

/* Write the next transmit byte.

SPI2BUF = bVal;

/* Wait for receive byte.

while (SPI2STATbits.SPIRBF == 0);

/* Put the received byte in the buffer.

bRx = SPI2BUF;

return bRx;

}