WIT2450FG - RFM - Datasheet.Live

WIT2450

2.4GHz Spread Spectrum Wireless Industrial Transceiver

Integration Guide

Important Regulatory Information

Cirronet Product FCC ID: HSW-2450

IC 4492A-2450

Note: This unit has been tested and found to comply with the limits for a Class A digital device,

pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection

against harmful interference when the equipment is operated in a commercial environment. This

equipment generates, uses, and can radiate radio frequency energy and, if not installed and used

in accordance with the instruction manual, may cause harmful interference to radio

communications. Operation of this equipment in a residential area is likely to cause harmful

interference in which case the user will be required to correct the interference at their expense.

FCC s MPE Requirements

Information to user/installer regarding FCC s Maximum Permissible Exposure (MPE) limits.

Notice to users/installers using the 24 dBi parabolic dish antenna in conjunction with a ll Cirronet

RF products.

FCC rules limit the use of this antenna, when connected to Cirronet RF prod ucts for point-to-point

applications only. It is the responsibility of the installer to ensure that the system is prohibited from

being used in point-to-multipoint applicati ons, omni-directional applications, and appli cation s where there

are multiple co-located intentional radiators tran smitting the same information. Any other mode of

operation using this antenna is forbi dden.

Notice to users/installers using the following fixe d antennas, with Cirronet RF prod ucts:

Andrews 24dBi parabolic d i sh

Andrews 18dBi parabolic d i sh

Cushcraft 15dBi Yagi,

Mobile Mark 14dBi Corner Reflector,

Mobile Mark 9dBi Corner Reflector

The field strength radiated by any one of these

antennas, when connected to Cirronet RF

products, may exce ed FCC mandated RF

exposure limits. FCC rules requi re

professional installation of these antennas in

such a way that the general public will not be

closer than 2 m from the radiating aperture of

any of these antennas. End users of these

systems must also be informed that RF

exposure limits may be exceeded if personnel

come closer than 2 m to the apertures of any of

these antennas.

Notice to users/installers using the following mobile antenn as, with Cirronet RF products:

Mobile Mark 12dBi omni-di rectio nal,

Mobile Mark 9dBi omni-directional,

MaxRad 5dBi whip,

Cirronet Patch antenna,

Ace 2dBi dipole,

Mobile Mark 2dBi Stub

The field strength radiated by any one of these

antennas, when connected to Cirronet RF

products, may exce ed FCC mandated RF

exposure limits. FCC rules requi re

professional installation of these antennas in

such a way that the general public will not be

closer than 20 cm from the radiating aperture

of any of these antennas. End users of these

systems must also be informed that RF

exposure limits may be exceeded if personnel

come closer than 20 cm to the apertures of any

of these antennas.

Declaration of Conformity

Warning! The RLAN transceiver within this device uses a band of frequencies that are not completely harmonized

within the European Community. Before using, please read the European Operation Section of the Products User’s

Guide for limitations.

0889 is the identification number of RADIO FREQUENCY INVESTIGATION LTD - Ewhurst Park, Ramsdell RG26

5RQ Basingstoke, United Kingdom – the Notified Body having performed part or all of the conformity assessment on

the product.

The WIT2450 to which this declaration relates is in conformity with the essential requirements of the R&TTE

directive 1999/5/EC and complies with the following standards and/or other normative documents:

For Interfaces For RLAN Transceiver

EN 55022

EN 55024 EN 300 328

EN 301 489 -1, -17

EN 60950

Use Within the European Union

The WIT2450 is intended for use within the European Community States and in the following non-European Union

States: Norway & Switzerland

Use of the WIT2450 in France

When used in France, t he WI T2 41 0 can o nl y be operat ed with the France hopping pattern selected. This is

accomplished by setting the pe parameter to 1. Refer to European Union Settings in this manual for details.

Canadian Department of Communications Industry Canada (IC) Notice

This apparatus complies with Health Canada’s Safety Code 6 / IC RSS 102.

"To prevent radio interference to the licensed service, this device is intended to be

operated indoors and away from windows to provide maximum shielding. Equipment (or

its transmit antenna) that is installed outdoors may be subject to licensing."

ICES-003

This digital apparatus does not exceed the Class B limits for radio noise emissions from

digital apparatus as set out in the radio interference regulations of Industry Canada.

Le présent appareil numérique n'émet pas de bruits radioélectriques dépassant les limites applicab les aux appareils

numériques de Classe B prescrites dans le règlement sur le brouillage radioélectrique édicté par Industrie Canada.

TABLE OF CONTENTS

1. INTRODUCTION ......................................................................................................................6

1.1. Why Spread Spectrum? .......................................................................................................7

1.2. Frequency Hopping vs. Direct Sequence.............................................................................8

2. RADIO OPERATION..............................................................................................................10

2.1. Synchronization and Registration......................................................................................10

2.2. Data Transmission .............................................................................................................11

2.2.1. Point-to-Point...........................................................................................................11

2.2.2. Point-to-Multipoint ..................................................................................................12

2.2.3. Handle Assignment..................................................................................................12

2.2.4. TDMA Operation.....................................................................................................13

2.2.5. Full Duplex Communication....................................................................................15

2.2.6. Error-free Packet Transmission Using ARQ............................................................15

2.3. Modes of Operation...........................................................................................................16

2.3.1. Control and Data Modes ..........................................................................................16

2.3.2. Power Down Mode ..................................................................................................16

2.3.3. Low Power Mode and Duty Cycling .......................................................................17

2.3.4. RF Flow Control Mode............................................................................................17

2.3.5. Co-Existing with 802.11b Networks........................................................................18

2.3.6. European Union Settings .........................................................................................18

3. PROTOCOL MODES ..............................................................................................................19

3.1.1. Data Packet ..............................................................................................................21

3.1.3. Connect Packet.........................................................................................................22

3.1.4. Disconnect Packet (base only, receive only) ..........................................................22

4. MODEM INTERFACE............................................................................................................23

4.1. Interfacing to 5-Volt Systems............................................................................................24

4.2. Evaluation Unit and OEM Module Differences................................................................24

4.3. Three Wire Operation........................................................................................................24

4.4. Power-On Reset Requirements..........................................................................................25

4.6. Received Signal Strength Indicator ...................................................................................26

5. MODEM COMMANDS...........................................................................................................27

5.1. Serial Commands...............................................................................................................27

5.2. Network Commands..........................................................................................................29

5.3. Protocol Commands...........................................................................................................31

5.4. Status Commands ..............................................................................................................34

5.5. Memory Commands ..........................................................................................................35

5.6. Modem Command Summary.............................................................................................37

6. WIT2450 DEVELOPER’S KIT ...............................................................................................38

7. WinCOM...................................................................................................................................39

7.1. Starting the program ..........................................................................................................41

7.2. Function Keys....................................................................................................................44

7.3. WinCom Tools...................................................................................................................45

7.4. Script Commands...............................................................................................................47

7.5. Demonstration Procedure ..................................................................................................49

8. Troubleshooting........................................................................................................................50

9. APPENDICES ..........................................................................................................................52

9.1. Technical Specifications....................................................................................................52

9.1.1. Ordering Information...............................................................................................52

9.1.2. Power Specifications................................................................................................52

9.1.3. RF Specifications.....................................................................................................52

9.1.4. Mechanical Specifications .......................................................................................52

9.2. Serial Connector Pinouts ...................................................................................................53

9.3. Approved Antennas ...........................................................................................................53

9.4. Technical Support..............................................................................................................54

9.5. Reference Design...............................................................................................................55

9.6. Mechanical Drawing – WIT2450......................................................................................56

10. Warranty .................................................................................................................................57

Conventions:

All Hexadecimal Numbers are written in New Courier font, 10 pt Bold as shown here: 30H

WIT2450

1. INTRODUCTION

From the leader in robust, high-performance wireless modules comes the next

generation of low-cost 2.4GHz spread spectrum OEM modules. The Cirronet WIT2450

provides the unique combination of highly integrated low-cost components with

Cirronet’s high performance, high-reliability RF know-how that has made Cirronet

products the first choice of designers for mission critical applications. With the

WIT2450, designers get that same mission critical reliability and robustness but at a

price that allows use in a wide variety of cost-sensitive applications.

The WIT2450 radio transceiver provides reliable wireless connectivity for either

point-to-point or multipoint applications. Frequency hopping spread spectrum

technology ensures maximum resistance to noise and multipath fading and robustness in

the presence of interfering signals, while operation in the 2.4GHz ISM band allows

license-free use and worldwide compliance. A simple serial interface supports

asynchronous data up to 230400 bps. An on-board 1 KB buffer and an error-correcting

over-the-air protocol provide smooth data flow and simplify the task of integration with

existing applications.

• Multipath fading impervious

frequency hopping

technology with 95

frequency channels.

• Meets FCC rules 15.247

and ETS 300.328 for

worldwide license-free

operation.

• Supports point-to-point or

point to multipoint

applications.

• Simple serial interface

handles both data and

control at up to 230.4kbps.

• Low power 3.3v CMOS

signals • Selectable 10 mW, 63mW

or 250 mW transmit power.

• Superior range to 802.11

wireless Local Area

Network devices.

• Dynamic TDMA slot

assignment that

maximizes throughput.

• Transparent ARQ protocol

w/512 byte buffer ensures

data integrity.

• Built-in data scrambling

reduces possibility of

eavesdropping.

• Digital addressing supports

up to 64 networks, with 62

remotes per network.

• Nonvolatile memory stores

configuration when

powered off.

• Fast acquisition typically

locks to hopping pattern in

2 seconds or less.

• Smart power management

features for low current

consumption.

WIT2450

1.1. Why Spread Spectrum?

The radio transmission channel is very hostile, corrupted by noise, path loss and

interfering transmissions from other radios. Even in a pure interference-free

environment, radio performance faces serious degradation through a phenomenon

known as multipath fading. Multipath fading results when two or more reflected

rays of the transmitted signal arrive at the receiving antenna with opposing phase,

thereby partially or completely canceling the desired signal. This is a problem

particularly prevalent in indoor installations. In the frequency domain, a multipath

fade can be described as a frequency-selective notch that shifts in location and

intensity over time as reflections change due to motion of the radio or objects within

its range. At any given time, multipath fades will typically occupy 1% - 2% of the

2.4 GHz band. This means that from a probabilistic viewpoint, a conventional radio

system faces a 1% - 2% chance of signal impairment at any given time due to

multipath.

Spread spectrum reduces the vulnerability of a radio system to interference from

both jammers and multipath f ading by distributing the transmitted signal over a

larger region of the frequency band than would otherwise be necessary to send the

information. This allows the signal to be reconstructed even though part of it may be

lost or corrupted in transit.

Figure 1

Narrowband vs. spread spectrum in the presence of interference

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1.2. Frequency Hopping vs. Direct Sequence

The two primary approaches to spread spectrum are direct sequence (DS) and

frequency hopping (FH), either of which can generally be adapted to a given

application. Direct sequence spread spectrum is produced by multiplying the

transmitted data stream by a much faster, noise-like repeating pattern. The ratio by

which this modulating pattern exceeds the bit rate of the baseband data is called the

processing gain, and is equal to the amount of rejection the system affords against

narrowband interference from multipath and jammers. Transmitting the data signal

as usual, but varying the carrier frequency rapidly according to a pseudo-random

pattern over a broad range of channels produces a frequency hopping spectrum

system.

Figure 2

Forms of spread spectrum

One disadvantage of direct sequence systems is that due to spectrum constraints and

the design difficulties of broadband receivers, they generally employ only a minimal

amount of spreading (typically no more than the minimum required by the regulating

agencies). For this reason, the ability of DS systems to overcome fading and in-band

jammers is relatively weak. By contrast, FH systems are capable of probing the

entire band if necessary to find a channel free of interference. Essentially, this

means that a FH system will degrade gracefully as the channel gets noisier while a

DS system may exhibit uneven coverage or work well until a certain point and then

give out completely.

Because it offers greater immunity to interfering signals, FH is often the preferred

choice for co-located systems. Since direct sequence signals are very wid e, they

tend to offer few non-overlapping channels, whereas multiple hoppers may

interleave with less interference. Frequency hopping does carry some disadvantage

in that as the transmitter cycles through the hopping pattern it is nearly certain to

visit a few blocked channels where no data can be sent. If these channels are the

same from trip to trip, they can be memorized and avoided; unfortunately, this is

generally not the case, as it may take several seconds to completely cover the hop

WIT2450

sequence during which time the multipath delay profile may have changed

substantially. To ensure seamless operation throughout these outages, a hopping

radio must be capable of buffering its data until a clear channel can be found. A

second consideration of frequency hopping systems is that they require an initial

acquisition period during which the receiver must lock on to the moving carrier of

the transmitter before any data can be sent, which typically takes several seconds. In

summary, frequency hopping systems generally feature greater coverage and channel

utilization than comparable direct sequence systems. Of course, other

implementation factors such as size, cost, power consumption and ease of

implementation must also be considered before a final radio design choice can be

made.

As an additional benefit, RF spectrum has been set aside at 2.4 GHz in most

countries (including the U.S.) for the purpose of allowing compliant spread spectrum

systems to operate freely without the requirement of a site license. This regulatory

convenience alone has been a large motivation for the industry-wide m ove toward

spread spectrum.

WIT2450

2. RADIO OPERATION

2.1. Synchronization and Registration

As discussed above, frequency hopping radios periodically change the frequency at

which they transmit. In order for the other radios in the network to receive the

transmission, they must be listening to the frequency over which the current transmission

is being sent. To do this, all the radios in the net must be synchronized and must be set to

the same hopping pattern.

In point-to-point or point-to-multipoint arrangements, one radio module is designated as

the base station. All other radios are designated remotes. One of the responsibilities of

the base station is to transmit a synchronization signal to the remotes to allow them to

synchronize with the base station. Since the remotes know the hopping pattern, once they

are synchronized with the base station, they know which frequency to hop to and when.

Every time the base station hops to a different frequency, it immediately transmits a

synchronizing signal.

When a remote is powered on, it rapidly scans the frequency band for the synchronizing

signal. Since the base station is transmitting over 95 frequencies and the remote is

scanning 95 frequencies, it can take several seconds for a remote to synch up with the

base station.

Once a remote has synchronized with the base station, it must request registration from

the base station. The registration process identifies to the base station the rem otes from

which transmissions will be received and not discarded. Registration also allows tracking

of remotes entering and leaving the network. The base station builds a table of serial

numbers of registered remotes. To improve efficiency, the 24-bit remote serial number is

assigned a 6-bit “handle” number. Two of these are reserved for system use, thus each

base station can register 62 separate remotes. This handle is how user applications will

know the remotes. Note that if a remote leaves the coverage area and then re-enters, it

may be assigned a different handle.

To detect if a remote has gone offline or out of range, the registration must be “renewed”

once every 256 hops. Registration is completely automatic and requires no user

application intervention. When the remote is registered, it will receive several network

parameters from the base. This allows the base to automatically update these network

parameters in the remotes over the air. Once a parameter has been changed in the base, it

is automatically changed in the remotes. The parameters that are automatically changed

are hop duration and the duty cycle.

At the beginning of each hop, the base station transm its a synchronizing signal. After the

synchronizing signal has been sent, the base will transmit any data in its buffer unless

data transmit delay has been set. The data transmit delay parameter allows for the

transmission of groups of continuous data in transparent mode (protocol mode 00H). The

amount of data that the base station can transmit per hop is determined by the base slot

WIT2450

size parameter. The maximum amount of data sent by a base station per hop is 208 bytes.

If there is no data to be sent, the base station will not transm it until the next frequency.

The operation for remo tes is similar to the base station without the synchronizing signal.

The amount of data a remote can send on one hop is dependent upon the hop duration,

the base slot size and the number of registered remotes. 212 bytes per hop is the

maximum data length a remote can transmit per hop, subject to limitations imposed by

the hop duration, the base slot size and the number of registered remotes. A detailed

explanation of this relationship is provided in Section 2.2.3. Minimum data length and

data transmit delay operate the same as with the base station.

Except for the registration process which occurs only when a remote logs onto the

network, the whole procedure is repeated on every frequency hop. Refer to the section

on Modem Commands for complete details on parameters affecting the transmission of

data.

2.2. Data Transmission

The WIT2450 supports two network configurations: point-to-point and point-to-

multipoint. In a point-to-point network, one radio is set up as the base station and the

other radio is set up as a remote. In a point-to-multipoint network, a star topology is used

with the radio set up as a base station acting as the central communications point and all

other radios in the network set up as remotes. In this configuration, all communications

take place between the base station and any one of the remotes. Remotes cannot

communicate directly with each other.

2.2.1. Point-to-Point

In point-to-point mode, unless data transmit delay or minimum data length have been set,

the base station will transmit whatever data is in its buffer limited to 208 bytes or as

limited by the base slot size. If the base station has more data than can be sent on one

hop, the remaining data will be sent on subsequent hops. In addition to the data, the base

station adds some information to the transmission over the RF link. It adds the address of

the remote to which it is transmitting, even though in a point-to-point mode there is only

one remote. It also adds a sequence number to identify the transmission to the remote.

This is needed in the case of acknowledging successful transmissions and retransmitting

unsuccessful transmissions. Also added is a 24-bit CRC to allow the base to check the

received transmission for errors. When the remote receives the transmission, it will

acknowledge the transmission if it was received without errors. If no acknowledgment is

received, the base station will retransmit the same data on the next frequency hop.

In point-to-point mode, a remote will transmit whatever data is in its buffer up to the limit

of its maximum data length. If desired, minimum data length and data transmit delay can

also be set, which force the remote to wait until a certain amount of data is available or

the specified delay is exceeded before transmitting. If the remote has more data than can

be sent on one hop, it will send as much data as possible as a packet, adding its own

WIT2450

address, a packet sequence number and 24-bit CRC. These additional bytes are

transparent to the user application if the protocol mode is 00H (which is the default). In

the event a remote has more data to send, the data will be sent on subsequent hops. If the

transmission is received by the base station without errors, the base station will

acknowledge the transmission. If the remote does not receive an acknowledgment, it will

retransmit the data on the next frequency hop. To the user application, acknowledgments

and retransmissions all take place behind the scenes without the need for user

intervention.

The WIT2450 has a point-to-point direct mode (wu) which fixes the remote radio’s

handle at 00H. This mode is recommended for point-to-point applications, especially if

the remote is likely to periodically leave and re-enter the coverage area of the base. See

section 5.2 Network Commands for details of this mode.

2.2.2. Point-to-Multipoint

In point-to-multipoint mode, data sent from the user application to the base station must

be packetized by the user application unless the remote device can distinguish between

transmissions intend ed for it and transmissions intended for other remote devices. This is

necessary to identify the remote to which the base station should send data. When the

user packet is received by the remote, if the remote is in transparent mode (protocol mode

0), the packetization bytes are stripped by the remote. In this instance the remote host

receives just data. If the remote is not in transparent mode, the remote host will receive

the appropriate packet header as specified by the remote’s protocol mode. Refer to the

section Protocol Modes for details on the various packet formats.

When a remote sends data to a base station in point-to-multipoint mode, the remote host

does not need to perform any packetization of the data. Remotes can operate in

transparent mode even though the base is operating in a packet mode. The remote will

add address, sequence and CRC bytes as in the point-to-point mode. When the base

station receives the data, the base station will add packetization header bytes according to

its protocol mode setting.

2.2.3. Handle Assignment

Handles are used to reduce overhead by not sending the unique 24-bit serial number ID

of a remote when sending or receiving data. The use of the various protocol modes

causes the base radio to issue CONNECT packets when a new remote registers with the

base. In addition to indicating the presence of a new remote, the CONNECT packets

provide the current relationship between remote serial numbers and handles.

When a remote links to a base and requests registration, it requests by default that it be

assigned handle 00H. This default request can be changed by the Set Default Handle

command. If that handle is not currently in use by another remote, the base will assig n

that handle to the remote. If the requested handle is already in use by another remote, the

base will assign the next higher handle that is available. Thus, if a remote requests

WIT2450

handle 00H and that handle is already assigned, the base will assign the remote handle

01H if that is available. If 01H is already assigned, the base will assign handle 02H is that

is available and so on.

When a remote leaves the coverage area of the base or otherwise loses link, e.g. the

remote was turned off or put into sleep mode, the base detects this event when the remote

does not renew its registration within 255 hops. With the default setting of 10msec per

hop, this could be as along as 2.55 seconds. If within this time the remote re-establishes

link with the base, the previous handle assigned to this remote will still be marked active

in the base radio. Thus the remote will be assigned a new handle. If the base radio is in

one of the protocol modes, a new CONNECT packet will be issued indicating the current

handle assigned to the remote. The remote is identified by the serial number that is

contained in the CONNECT packet.

If the radio is to be used in a point-to-point mode where there is only one base and one

remote, using the point-to-point mode command of the radios will override this handle

mechanism and always assign the remote the same handle.

2.2.4. TDMA Operation

For applications needing guaranteed bandwidth availability, the TDMA operation of the

WIT2450 can meet this requirement. In the WIT2450 TDMA scheme, each remote has

an assigned time slot during which it can transmit. The base station time slot is set

independently of the remote time slots through the Set Base Slot Size command. The

base station assigns each remote a time slot and informs the remotes of the size of the

time slot. All remote time slots are the sam e size that is determined by the number of

remotes registered with the base station. The slot size is a dynamic variable that changes

as the number of registered remotes changes. The remotes are continually updated with

the time slot size. This approach continually maximizes the data throughput. The base

station divides the amount of time available per hop by the number of registered rem o tes

up to a maximum of 16 times slots per hop. If the number of registered remotes is greater

than 16, the time slots will be spread across the required number of hops. For networks

with more than 16 possible remotes, the Set Duty Cycle command must be used to specify

a duty cycle -- the number of hops over which the time slots must be spread. For 1 to 16

remotes, no duty cycle is required; for 17 to 32 remotes a duty cycle of at least ½ is

required; and for 33 to 62 remotes a duty cycle of ¼ or more is necessary. An added

benefit of using the power save mode to set a duty cycle is improved average current

consumption efficiency. Refer to the Status Commands section for details of this

command.

When setting up a network, keep in mind that time slot length, maximum packet size and

hop duration are all interrelated. The hop duration parameter will determine the time slot

size and the maximum amount of data that can be transmitted per hop by the remotes.

There is a hard limit of the absolute maximum amount of data that can be sent on any

given hop of 212 bytes regardless of any parameters. (Note that this is different than the

208 byte maximum for the base station.) The base station requires 2.64 ms overhead for

WIT2450

tuning, the synchronization signal and parameter updating, as well as a guard time of

417µs between each remote slot. Thus the amount of time allocated per remote slot is

roughly:

hop duration – base slot – 2.64ms - ( # of registered remotes)·417µs

( # of registered remotes)

Take for example a network comprised of a base station and 10 remotes. A hop duration

of 10 ms is chosen. We decide that the base station needs to be able to send up to 32

bytes each hop (equivalent to a capacity for the base of ~ 32 kbps). Counting the 2.64ms

overhead for the base packet and making use of the fact that our RF rate is 460.8 kbps,

we determine that the base slot requires approximately:

Each remote time slot will be:

10 ms – 3.2 ms – (10)·0.417 ms

32·8

460.8kbps

+ 2.64 ms = 3.20

= 0.263ms

From our RF data rate of 460.8kbps we see that it takes 17.36 µs to send a byte of data,

so each remote will be able to send up to

= 15.1 bytes of data per hop.

0.263 ms

7.36

However, the WIT2450 sends data in groups of 4 bytes. Thus, each remote will be able to

send 12 bytes of data. If the WIT2450 is using a protocol mode, the packet overhead is

stripped off (including start and stop bits) before transmission and does not need to be

considered when calculating RF capacity.

So in this example, the total capacity per remote would be:

12 bytes

10 ms

= 12 kbps

If we figure a minimum margin of safety for lost packets and retransmissions of about

20%, we see that this would be more than sufficient to support 9.6 kbps of continuous

data per remote. It is also useful to remember that the asynchronous data input to the

WIT2450 is stripped of its start and stop bits during transmission by the radio, yielding a

"bonus" of 10/8 or 25% in additional capacity.

The above calculations are provided as a means of estimating the capacity of a multipoint

WIT2450 network. To determine the precise amount of capacity, you can actually set up

the radio system and then query the maximum data length from one of the remotes in

control mode to discover its exact setting. Divide this number by the hop duration as

above to get the remote's exact capacity.

WIT2450

2.2.5. Full Duplex Communication

From an application perspective, the WIT2450 communicates in full duplex. That is,

both the user application and the remote terminal can be transmitting data without

waiting for the other to finish. At the radio level, the base station and remotes do not

actually transmit at the same time. If they did, the transmissions would collide. As

discussed earlier, the base station transmits a synchronization signal at the beginning of

each hop followed by a packet of data. After the base station transmission, the remotes

will transmit. Each base station and remo te transmission may be just part of a complete

transmission from the user application or the remote terminal. Thus, from an application

perspective, the radios are communicating in full duplex mode since the base station will

receive data from a remote before completing a transmission to the remote.

2.2.6. Error-free Packet Transmission Using ARQ

The radio medium is a hostile environment for data transmission. In a typical office or

factory environment, 1% - 2% of the 2.4GHz frequency band may be unusable at any

given time at any given station due to noise, interference or multipath fading. For

narrowband radio systems (and also many spread spectrum radio systems which use

direct sequence spreading), this would imply a loss of contact on average of over 30

seconds per hour per station. The WIT2450 overcomes this problem by hopping rapidly

throughout the band in a pseudo-random pattern. If a message fails to get through on a

particular channel, the WIT2450 simply tries again on the next channel. Even if two

thirds of the band is unusable, the WIT2450 can still communicate reliably.

Data input to the WIT2450 is broken up by the radio into packets. A 24-bit checksum is

attached to each packet to verify that it was correctly received. If the packet is received

correctly, the receiving station sends an acknowledgment, or ACK, back to the transmitting

station. If the transmitter doesn't receive an ACK, at the next frequency hop it will attempt

to send the packet again. When ARQ is enabled, the transmitting radio will attempt to

send a packet packet attempts limit times before discarding the packet. A value of 00H

disables ARQ. When it is disabled, any transmission received with errors is discarded. It

is the responsibility of the user application to track missing packets. A second parameter,

ARQ Mode, allows the choice between using ARQ to resend unsuccessful transmissions

or always sending a transmission packet attempts limit times regardless of the success or

failure of any given transmission.

All of this error detection and correction is transparent to the user application. All the

user application sees is error-free data from the modem. However, if the ARQ mode is

disabled, transmissions with errors are discarded, and missing data detection will be the

responsibility of the user application. Refer to the Protocol Commands section for

complete details.

WIT2450

2.3. Modes of Operation

2.3.1. Control and Data Modes

The WIT2450 has two modes of operation: Control mode and Data mode. When in

Control Mode, the various radio and modem parameters can be modified. When in Data

Mode, only data can be transmitted. The default mode is Data Mode. There are two

ways to enter Control Mode. The first way is to assert the Configure (CFG) pin on the

modem. Upon entering Control Mode, the modem will respond with a > prompt. After

each command is entered, the modem will again respond with a > prompt. As long as the

CFG pin is asserted, data sent to the modem will be interpreted as command data. Once

the CFG pin is deasserted, the modem will return to Data Mode.

The second method for entering Control Mode is to send the escape sequence :wit2410

(all lower case) followed by a carriage return. In the default mode, the escape sequence

is only valid immediately after power up or after deassertion of the Sleep pin on the

modem. The modem will respond in the same way with a > prompt. To return to Data

Mode, enter the Exit Modem Control Mode command, z>, or assert and deassert the

Sleep pin. There are three modes for the escape sequence, controlled by the Set Escape

Sequence Mode command, zc:

zc = 0 Escape sequence disabled

zc = 1 Escape sequence available once at startup (default setting)

zc = 2 Escape sequence available at any time

The zc2 mode setting is useful if the user application has a need to change the modem

settings "on the fly". In this mode the escape sequence is always enabled and m ay be

sent at any time after a pause of at least 20ms. The modem will respond in the same way

as when in the default mode. It is necessary to issue the Exit Modem Control Mode

command, z>, before resuming data transmission.

Note: The escape sequence must be interpreted as data until the last character is received

and as such may be transmitted by the modem to any listening modems.

2.3.2. Power Down Mode

To save power consumption for intermittent transmit applications, the WIT2450 supports

a Power Down Mode. Power Down Mode enables the user to achieve exceptionally low

current consumption (typically less than 1 uA) in non-active units. Pin number 14

(fourteen) is a device input, a low voltage on this pin (0-Vdc to 1-Vdc) puts the device in

power down. A high voltage on this pin (3.3-Vdc to 5Vdc) puts the device in normal

operating condition. This mode allows the radio to be powered off while the terminal

device remains powered. After leaving Power Down Mode, the radio must re-

synchronize with the base station and re-register.

Note: This pin cannot be left unconnected.

If Power Down is not needed, this pin must be tied to 3.3v.

WIT2450

2.3.3. Low Power Mode and Duty Cycling

To conserve power, WIT2450 remotes power down the receiver and transmitter between

hops when not in use. Base stations must remain active all the time to handle any

transmission from any remote. Remotes can save even more power by enabling the duty

cycle feature. This feature causes a remote to power down for 2N frequency hops where

1/2N is the duty cycle. Rather than attempting to transmit on every frequency hop when

data is in the transmit buffer, a remote will attempt to transmit only every 2N hops.

Roughly speaking, this will proportionately reduce the average power consumption while

increasing average latency. When there are more than 16 remotes being operated, duty

cycling must be enabled since a maximum of 16 time slots is available per hop.

When a remote radio is powered up but is out of range of a base station, it will

continuously scan the frequency bands for the presence of a base radio. During this

scanning, the radio can consume up to 160 mA of current.

2.3.4. RF Flow Control Mode

Because of slight differences in baud rates between transmitting and receiving hosts,

when sending large amounts of data (100’s of KB) in one direction in a point-to-point

application, it is possible to overrun the receive buffer of the receiving radio. For

example a nominal 115.2Kbaud at the transmitting radio’s host might really be 115,201

and at the receiving radio’s host it might be 115,199. This is sim ilar to a situation where

the transmitting radio is sent data at a higher baud rate than the baud rate at which data is

received by the receiving host. To compensate for the variations in nominal baud rates,

the WIT2450 supports an RF flow control mode for point-to-point operation. In this

mode, when the receive buffer of the receiving WIT2450 is close to full, the receiving

WIT2450 stops acknowledging transmissions. The transmitting radio is set to infinite

retries which invokes the RF flow control mode (See Set Packet Attempts Limit in Section

5.3). The receiving radio will not begin acknowledging transmissions from the

transmitting radio until more room in the receive buffer has become available. This will

cause data in the transmit buffer of the transmitting radio to back up. If it backs up to the

point where the transmit buffer fills up, the transmitting radio will deassert CTS stopping

data from the transmitting radio’s host device. Once room is available in the receiv ing

radio’s buffer, the receiving radio will begin acknowledging transmissions from the

transmitting radio allowing the transmitting radio’s buffer to begin to empty which will

cause the transmitting radio to reassert CTS. Either one or both of the radios in a point-

to-point installation can be configured for the RF flow control. If this mode is invoked in

a point-to-multipoint installation, communications with all radios will be stopped when

any one radio’s receive buffer becomes full.

WIT2450

2.3.5. Co-Existing with 802.11b Networks

In some cases, if a WIT2450-based network is located in close proximity to an 802.11b

network, the WIT2450-based network can interfere with the 802.11b network. To avoid

causing this interference, the WIT2450 radio supports a selection of hopping patterns that

avoid the various 802.11b direct sequence channels. These limited band hopping patterns

allow WIT2450-based networks to be used with 802.11b networks without impacting the

performance of the 802.11b networks. The hopping pattern is selected using the pe

command. Please refer to the section 5.3 Protocol Commands for details.

2.3.6. European Union Settings

When operating the WIT2450 in France, a limited frequency mode must be selected. The

Pe6 value avoids 802.11b bands 11 & 12 is compliant with the French regulatory

standards of 2400-2450MHz. To select the limited frequency band for operation in

France, at the > configuration mode prompt enter:

pe6<CR>

Save this setting by typing:

m><CR>

The limited frequency operation will take effect immediately and will be saved into

memory for use when power is cycled.

Use of the WIT2450 within the European Union is limited to a maximum transmit power

including antenna gain of 20dBm. If gain antennas are to be used, the low power setting

of the WIT2450 must be selected using the wp command (See Section 5.2 Network

Commands). With the low power setting of 10dBm at the antenna connector, a maximum

of 10dB of antenna gain may be used. With the mid power setting of 18dBm, a

maximum of 2dB of antenna gain may be used. To select low power mode, at the >

configuration mode prompt enter:

wp0<CR>

To select mid power mode, at the > configuration mode prompt enter:

wp1<CR>

To save this parameter in non-volatile memory type:

WIT2450

3. PROTOCOL MODES

In point-to-point applications, it is generally desired that the radios operate in a

transparent mode. That is, raw unformatted data is sent from the host to the radio and is

received as raw data from the receiving end. The addressing and error detection and

correction are still performed by the radios, but it is transparent to the user application.

To set up a point-to-point network, one radio has to be set up as a base station. When the

radios are powered on, the base station will send out the synchronization signal at the

beginning of each hop. The remote will synchronize with the base and automatically

request registration. Once the remote is registered, the radios can transmit data. Protocol

mode operation is available in point-to-point mode if desired.

If the base station is to be responsible for directing data to a specific remote in point-to-

multipoint mode, the data sent to the base station by the user application must adhere to a

packet format. This allows transmissions from the base station to be directed to a specific

remote. Data received by a base station from a remote is similarly formatted to identify

to the user application the remote that sent the transmission. The remotes may still use

transparent mode without formatting to send data to the base, if desired. The WIT2450

supports 10 protocol formats that are described in detail below. The protocol format is

selected through the Set Protocol Mode command.

Base and remote radios can use protocol modes to insure that a packet is transmitted to

the base without being broken up over multiple hops. The data length value in the data

packet becomes the effective minimum packet length and maximum packet length for that

packet. Note that if the remote data length is set to a number of bytes that is longer than

the number of bytes that can be transmitted by a remote on a single hop, the packet will

be discarded. For the base, this value is set by the Set Base Slot Size command. For

remotes this value is dynamically available through the Get Maximum Data Length

command or may be calculated based on the maximum number of remotes that can ever

be registered at one time. See Sections 5.3 and 2.2.4 respectively. Also note that using

protocol modes effectively disables Data Transmit Delay. This m eans that a packet will

not be transmitted until the entire packet has been sent to the radio, regardless of the

amount of time it takes.

If the remote hosts can determine what data is directed to them in point-to-multipoint

mode, the data can be sent to the base station without using a packet format. In this

situation, broadcast mode is selected at the base station by using the Set Default Handle

and selecting 3FH as the default handle. In this mode, the automatic retransmission of

unsuccessful transmissions is disabled. This is required since all of the remote modem s

will attempt to acknowledge each base transmission when ARQ is enabled.

Transmissions that are received with errors are discarded by the radio. The remote

devices must be able to detect a missing packet and request a retransmission by the base

device.

WIT2450

Protocol Modes Definitions

mode 00 Transparent mode used for point-to-point networks

or multipoint remotes; does not support any packet

types.

mode

01 This is the simplest protocol mode supporting Data

packets only. This mode is not recommended for

base radios. No CONNECT or DISCONNECT

packets are supported and no sequence numbers are

provided.

packet types supported: Data

mode

02 This mode includes notification when remotes are

registered or dropped through CONNECT and

DISCONNECT packets that are sent to the user

application at the base station and at the remote. No

sequence numbers are provided.

packet types supported: Data

CONNECT

DISCONNECT

modes 03 – 08 reserved for future use.

mode

09 This mode sends the protocol mode 01 packets

during transmit but receives data transparently.

mode 0A This mode sends the protocol mode 02 packets

during transmit but receives data transparently.

mode

0C This mode sends the protocol mode 04 packet

during transmit but receives data transparently.

modes 0D – 0F reserved for future use.

mode

11 This mode sends data transparently but supports

protocol mode 1 during reception.

mode

12 This mode sends data transparently but supports

protocol mode 2 during reception.

mode 14 This mode sends data transparently but supports

protocol mode 4 during reception.

WIT2450

3.1. Packet Formats

The byte formats for each packet type are shown in the table below. Packet fields are

organized to fall on byte boundaries. In the case of bit-level fields, most-significant bits

are on the left.

MRTP (WIT2410) packet types (modes 01-02):

Transmit and Receive:

Base DATA 1110 1001 00HH HHHH LLLL LLLL <0-208 bytes data>

Remote DATA 1110 1001 0000 0000 LLLL LLLL <0-212 bytes data>

Receive only:

CONNECT 1110 1001 10HH HHHH RRRR TTTT 00NN NNNN <3 byte remote ID>

DISCONNECT 1110 1001 11HH HHHH 0111 1111

H : handle number (0-63)

L : data length (0-208 for base, 0-212 for remote)

N : remote's previous network number (if roamed)

R : receive sequence number (from previous cell)

T : transmit sequence number (from previous cell)

Note that while the packet length can be set to 212, the maximum number of bytes

transmitted per hop is limited to the lesser of 212 or the length specified b y maximum data

length. Packets with a data length longer than that will be discarded and not sent. See

Get Maximum Data Length for more details.

3.1.1. Data Packet

Modes 01 & 02:

Base 1110 1001 00HH HHHH LLLL LLLL <0-208 bytes data>

Remote 1110 1001 0000 0000 LLLL LLLL <0-212 bytes data>

This packet carries user data. The handle number is the handle of the receiving remote.

When data is being sent from a remote to the base, no handle number is required. Up to

212 bytes (208 for base radios) of user data may be carried per data packet but no more

than is specified by the maximum data length parameter. The radio will not break up a

packet over multiple hops. Packets with a data length greater than maximum data length

will not be sent and will be discarded. This parameter is variable and depends on the

number of remotes currently registered.

Handle 63 is reserved for broadcast packets from the base to all remo tes.

Acknowledgment requests are not supported for broadcasts. For this reason, it is a good

idea to send broadcast messages several times to increase the odds of reaching all

remotes.

WIT2450

3.1.3. Connect Packet

1110 1001 10HH HHHH RRRR TTTT 00NN NNNN <3-byte remote ID> (base, receive only)

H : handle number (0-62)

R : receive sequence number (from previous cell)

T : transmit sequence number (from previous cell)

N : network number of the previous base (if roamed)

1110 1001 10HH HHHH RRRR TTTT 00NN NNNN <3-byte base ID> (remote, receive only)

H : handle number (0-62)

R : receive sequence number

T : transmit sequence number

N : network number of base

Remotes must go through an automatic registration process when roaming from one base

to another, after loss of contact, or when acquiring a base signal for the first time after

power up. The base then assigns the remote a handle value, may or may not assign it a

dedicated time slice depending on the user settings, and notifies the user application of

the new remote with a connect packet.

The network number of the last base the remote was connected to is given to aid user

software in resending orphan packets that may have been sent to the remote's previous

cell. If the remote has been powered up for the first time and this is the first base

contacted, the last base ID will be reported as 80H.

3.1.4. Disconnect Packet (base only, receive only)

1110 1001 11HH HHHH 0111 1111

H : handle number (0-62)

When a remote goes out of range or roams to another cell, the base issues a disconnect

packet to indicate that the remote is no longer available.

WIT2450

4. MODEM INTERFACE

Electrical connection to the WIT2450 is made through a 16-pin male header on the

modem module. The signals are 3.3-volt signals and form an RS-232 style asynchronous

serial interface. The table below provides the connector pinout.

Pin Signal Type Description

1 GND - Signal and chassis ground

2 TXD Input Transmit data. Input for serial data to be transmitted. In Control

Mode also used to transmit modem com mands to the modem.

3 RXD Output Receive data. Output for received serial data. In Control Mode,

also carries receive modem status fro m the modem.

4 Input

Configuration selector. Used to switch between Control and Data

Modes. Normally, CFG will be set for Data Mode. An internal 10K

pull-up enables Data Mode if this signal is left unconnected.

Control Mode is also accessible by transmitting an escape

sequence immediately after wake up or power up.

(0v) 1 = Control Mode

(3.3v) 0 = Data Mode

5 Input

Request to send. Gates the flow of receive data from the radio to

the user on or off. In normal operation this signal should be

asserted. When negated, the WIT2450 buffers re ceiv e data until

RTS is asserted.

(0v) 1 = Receive data (RxD) enabled

(3.3v) 0 = Receive data (RxD) disabled.

6 DTR Input Sleeps/wakes radio transceiver. In sleep mode all radio functions

are disabled. At wake up, any user programme d configuration

settings are refreshed from non-volatile memory, clearing any

temporary settings that may have been set.

(3.3v) 1 = Sleep Radio

(0v) 0 = Wake Radio

7 Output Data carrier detect. For remotes, indicates the remote has

successfully acquired the hopping pattern of the base station.

(0v) 1 = Carrier detected (synchronize d)

(3.3v) 0 = No carrier detected (not synch ronized)

8 Output Clear to send. Used to control transmit flow from the user to the

radio.

(0v) 1 = Transmit buffer not full, continue transmitting

(3.3v) 0 = Transmit buffer full, stop transmitting

9 RSSI Output Received Signal Strength Indicator (analog signal)

10-12 - - Reserved for future use. Do not connect.

13 RSSI

Strobe Output Indicates valid RSSI data. (3.3v) 1 = RSSI data valid

(0v) 0 = RSSI data invalid

14 Pdwn Input Power Down. 0 = Powe r down 3.3v to 5v = Active

Must be pulled high for radio to operate.

15 - - Reserved for future use. Do not connect.

16 Vcc - Positive supply. Min 3.3 v, 5.0 v nominal, 10.0 v max.

CFG

RTS

DCD

CTS

WIT2450

4.1. Interfacing to 5-Volt Systems

The modem interface signals on the WIT2450 are 3.3-volt signals. To interface to 5-volt

signals, the resistor divider network shown below must be placed between the 5-volt

signal outputs and the WIT2450 signal inputs. The output voltage swing of the WIT2450

3.3-volt signals is sufficient to drive 5-volt logic inputs.

2200

Ω

From 5v

Output

To 3.3v Input

4300

Ω

4.2. Evaluation Unit and OEM Module Differences

The evaluation unit has an RS-232 transceiver that translates RS-232 level signals to 3.3-

volt signals for input into the OEM module inside the evaluation unit. A typical

schematic is shown in Appendix 7.5. The OEM module does not have any type of RS-

232 transceiver and cannot handle the RS-232 voltages. This allows the OEM module to

be easily integrated into any 3.3-volt system without any logic signal translation. In order

for the OEM module to function properly several pins need to be driven low or tied to

ground. Pin 5 (RTS) and pin 6 (DTR) need to be pulled to ground on the 16-pin male

header. If you have the OEM module interfaced to an RS-232 transceiver, RTS and DTR

need to be pulled high on the transceiver side. In the evaluation unit, RTS and DTR are

pulled high on the transceiver side so the evaluation unit will work with these signals not

connected.

4.3. Three Wire Operation

The WIT2450 can be operated in a three wire configuration using just TxD, RxD and

Ground. To operate the WIT2450 in this configuration, the Sleep and RTS signals must

be tied to ground. These signals are pulled up on the WIT2450 module and if left

disconnected will put the radio into sleep mode and RTS will be deasserted. In addition,

Power Down Mode (Pin #14) must be tied high.

The WIT2450 does not support software flow control (XON/XOFF). Thus when using a

three wire configuration, there is no flow control. The radio configuration and/or the

application must insure the transmit and receive buffers do not overflow. The WIT2450

has a 512-byte transmit buffer and a 512-byte receive buffer. For example, the default

settings for the base slot size and hop duration are 08H and 90H respectively. The 08H

base slot size allows the base to send 32 bytes of data per hop. The 90H hop duration

WIT2450

provides a 10ms hop dwell time. These default settings provide a base throughput of

40kbps (Since the over the air transmission is synchronous, the 32kbps synchronous over

the air rate is equivalent to 40kbps asynchronous into the radio serial port). If the base

transmits continuously at a higher rate than this, unless the default settings are changed,

the transmit buffer will eventually overflow. To allow a higher base throughput, either

increase the base slot size or the hop duration or both. A similar analysis needs to be

performed for the remote radios. Refer to Section 2.2.3 TDMA Mode for the remote

throughput calculation.

4.4. Power-On Reset Requirements

The WIT2450 has an internal reset circuit that provides a reset signal to the

microprocessor if the supply voltage to the WIT2450 falls below 2.7-volts. Operation of

the microprocessor at voltages below this voltage is unspecified and can result in

corruption of the program memory. When the radio is first powered on, there is an inrush

current in excess of 250mA. The power supply in the host must be capable of sourcing

this current without the voltage falling below 2.7-volts at the radio. Failure of the power

supply to meet this requirement can result in “motorboating” of the radio where the

inrush current of the radio pulls the supply voltage below 2.7-volts causing the reset

circuit to fire which resets the radio removing the current requirement. Once the voltage

recovers to a level above 2.7-volts, the reset signal is removed from the radio which

causes the inrush current which causes the voltage to drop causing the reset circuit to fire

and so on.

WIT2450

4.6. Received Signal Strength Indicator

Pins 9 and 13 allow real-time assessment of received signal strength. The graph above

shows the relationship of the analog RSSI output voltage from Pin 9 vs. LNA input

power. The RSSI is approximately linear from -100 dBm to -31 dBm. The voltage level

at -100 dBm is .2V and the voltage level at -31 dBm is 1.25V which is the maximum

output voltage as shown in the chart. These values would correspond to 0FH and 60H

when using the wr command in Section 5.2 Network Commands.

The RSSI Strobe output indicates when a valid RSSI signal is present and a high signal

indicates a valid RSSI. The figures below show the relations hip between the RSSI signal

and the RSSI Strobe output.

WIT2450

5. MODEM COMMANDS

The WIT2450 is configured and controlled through a series of commands. These

commands are sent to the modem directly when the modem is in Control Mode when the

modem is in Data Mode if the escape sequence is enabled. The command syntax is the

same for either method, a one- or two-letter command followed by one or more

parameters. The modem will r espond with a two-byte message that indicates the new

modem parameter value. The commands are loosely grouped into five different

categories: Serial commands, Network commands, Protocol commands, Status

commands and Memory commands. Each command is described in detail below. In the

descriptions, brackets ([,]) are used to denote a set of optional argum ents. Vertical

slashes ( | ) separate selections. For example, given the string wn[?|0..3f], some legal

commands are wn?, wn0, wn3 and wna. Most commands which set a parameter also have

a ? option which causes the modem to respond with the current parameter setting, e.g.,

wn? Each modem command must be followed by either a carriage return or a line feed.

5.1. Serial Commands

These commands affect the serial interface between the modem and the host. The default

settings are 9600 bps and protocol mode 0.

Command Description

sd[?|01..BF] Set Data Rate Divisor

Data Rate Divisor (hex)

2400 bps = BF

9600 bps = 2F (default)

14400 bps = 1F

19200 bps = 17

28800 bps = 0F

38400 bps = 0B

57600 bps = 07

115200 bps = 03

230400 bps = 01

sp[?|00..14] Set Protocol Mode

00 = point-to-point transparent mode

01 = basic command and data only

02 = command, data and connection notification

03 – 08 = reserved for future use

09 = mode 01 during transmit, transparent receive

0A = mode 02 during transmit, transparent receive

0C = mode 04 during transmit, transparent receive

0D – 10 = reserved for future use

11 = transparent transmit, mode 01 during receive

12 = transparent transmit, mode 02 during receive

14 = transparent transmit, mode 04 during receive

WIT2450

Set Data Rate Divisor

Sets the serial bit rate between the modem and the host. This command takes effect

immediately and will require adjusting the host serial rate to agree. Nonstandard rates

may be programmed by entering a data rate divisor computed with the following formula:

DIVISOR = (460800/RATE)-1

Round all non-integer values down.

Set Protocol Mode

Enables the base station to operate in a multipoint network. Depending on the user

application, more or less acknowledgment may be desired by the application. Remotes

can operate in transparent mode even though the base station is operating in one of the

nontransparent modes.

When using a protocol mode, make sure to count in packet overhead when calculating the

time it will take to read data from th e module. Refer to the Section 3 on Protocol Modes

for details on each format.

WIT2450

5.2. Network Commands

Network commands are used to set up a WIT2450 network and to set radio addressing

and configuration.

Command Description

wb[?|0|1] Set Transceiver Mode

0 = remote (default)

1 = base station

wd[?|00-3f] Set Default Handle

Used to override automatic handle assignment by the base station

00 = default

wg[?|0|1] Enable Global Network Mode

0 = Link only to hop pattern specified by wn parameter (default)

1 = Link to any hop pattern, regardless of wn parameter

wl[?|0-ff] Set lockout key allowing network segregation beyond network number

0 = default

wn[?|0-3f]*

* = depends upon

the pe setting

Set Hopping Pattern or Network Number

0 = default

For pe0 wn = 0 to 3f

For pe1 - pe6 wn = 0 – 27

For pe7 wn = 0 – 16 (excluding 15)

For pe8 - peA wn = 0 – 14

wp[?|0|1|2] Set Transmit Power

0 = 10mW / 10dBm

1 = 63mW / 18dBm (default)

2 = 250mW / 24dBm

wr? RSSI - Read Receive Signal Strength

wu[?|0|1] Set Point-to-Point Direct Mode

0 = Multipoint mode (default)

1 = Point-to-point direct mode

Set Transceiver Mode

Sets modem operation as either base station or remote. Default is remote.

Set Default Handle

Sets handle number between 0 and 62 inclusive for a remote to request from the base

station. This command can be used in applications where it is desired to have specific

modems have specific handles. When specified for the base, the default handle

determines which remote it will address when transparent protocol mode is in effect.

When 3FH is specified for the base, broadcast mode is entered.

Enable Global Network Mode

For networks with multiple base stations, remotes are ord inarily only able to link to one

base station, set by the hopping pattern. Mode 1 enables the global mode that allows

remotes to link to any base station they can hear, acquiring whatever hop pattern is

WIT2450

required. In this mode a remote can only change base stations once it is no longer

registered with a base station.

Set Lockout Key

Allows further network segregation beyond the network number. This feature allows

multiple co-located networks in which global roaming is enabled. In global roaming, a

remote is allowed to link to any base regardless of the network number as long as the

lockout key agrees. By using different lockout keys, the bases to which remotes link can

be limited or segregated.

Set Hopping Pattern

The WIT2450 has 32 preprogrammed hopping patterns (also referred to as network

numbers). By using different hopping patterns, nearby or co-located networks can avoid

interfering with each other’s transmissions. Even if both networks tried to use the same

frequency, on the next hop they would be at different frequencies. Network numbers

above 32 recycle the same hopping patterns but may be used to distinguish between

networks. Note: This parameter varies depending on the

setting of pe (Alternative Frequency Band).

Set Transmit Power

The WIT2450 has three preset transmit power levels, 10mW (10dBm), 63mW (18dBm)

and 250mW (24dBm) measured at the RF connector. Control of the transmit power is

provided through this command. Default is 63mW / 18dBm.

Read Receive Signal Strength Indicator (RSSI)

This command reports the relative signal strength averaged over the last 10 hops. This

command returns a one byte value that is proportional to received signal strength and can

range from 00H to FFH. Typical values range from 0FH to 60H where the lower the

number the lower the received signal strength and the higher the number the higher the

received signal strength. This is a relative indication and does not directly correspond to

a field strength number. This is available only at the remotes as the base station is the

only source that transmits on a regular basis. Plus, in a point-to-multipoint network the

base will receive different signal strengths from each remote.

Set Point-to-Point Direct Mode

Sets point-to-point mode that is recommended for point-to-point applications, especially

where the remote radio is mobile and may leave and re-enter the range of the base. This

mode fixes the remote handle assignment to always be 00H and improves the re-

registration process. Must be set in both base and remote radios.

WIT2450

5.3. Protocol Commands

These commands can be used to tune the transceiver for optimum transmission of data

across the RF link. For most applications, the default values are adequate.

Command Description

pe[?|0-A] Set Alternative Frequenc y Band

0 = FCC/ETSI operation. (~2401 – 2471MHz) (d efault)

1 = (2431.3 – 2482.3 MHz) Avoids 802.11b bands 1 & 2

2 = (2400.2 – 2409.7 & 2440.8 – 2482.3 MHz) Avoids bands 3 & 4

3 = (2400.2 – 2418.3 & 2449.4 – 2482.3 MHz) Avoids bands 5 & 6

4 = (2400.2 – 2428.7 & 2459.8 – 2482.3 MHz) Avoids bands 7 & 8

5 = (2400.2 – 2437.3 & 2468.4 – 2482.3 MHz) Avoids bands 9 & 10

6 = (2400.2 – 2452.0 MHz) Avoids bands 11 & 12 (French compliant)

*** Only 16 networks are supported for pe7 and above ***

7 = (2421.7 – 2446.8 MHz)

Avoids (2401. 7 – 24 2 0.1 & 2449.6 – 247 9.1)MHz

8 = (2457.2 – 2482. 3 MH z) Avoids (240 1.7 – 2451.5)MHz

9 = (2400.2 – 2426. 1 MH z) Avoids (242 9.3 – 2479.1)MHz

A = (2431.3 – 2456.3 MHz)

Avoids (2401. 7 – 24 2 9. 3)MHz and (245 8.8 – 2479.1)MHz

ph[?|00-fe]

(base only)

Set Hop Duration

90H = default (=10ms)

pk[?|00-d0]

Set Minimum Data Length

01 = default

pl? (remote only)

Get Maximum Data Length (read only)

D4 = default (=212 bytes)

pn[?|01-3e]

(base only) Set Maximum Numbe r of Remotes

8 = default (=8 remotes)

pr[?|00-ff]

Set Packet Attempts Limit

8 = default

FF = infinite retry (RF flow control point-to-point only)

pt[?|00-ff]

Set Data Transmit Delay

00 = default

pv[?|0|1]

(base only)

Set Slot Assignment Mode

0 = default (dynamic slot assignment)

1 = static slot assignment

pw[?|00-2f]

(base only) Set Base Slot Size

8 = default (=32 bytes)

px[?|0|1] Set ARQ mode.

0 = ARQ enabled (default)

1 = ARQ disabled (redundant transmission)

Note: Incorrect setting of these parameters may result in reduced throughput or loss of data packets.

WIT2450

Set Alternative Frequency Band

This setting should be set to 0, for FCC-compliant operation in the US (this is the

default). When set to 1, avoids 802.11b bands 1 & 2. When set to 2, avoids 802.11b

bands 3 & 4. When set to 3, avoids 802.11b bands 5 & 6. When set to 4, avoids 802.11b

bands 7 & 8. When set to 5, avoids 802.11b bands 9 & 10. When set to 6, avoids 802.11b

bands 11 & 12 and is also compliant with French regulatory standards. When set to 7,

avoids (2401.7 – 2420.1)MHz and (2449.6 – 2479.1)MHz. When set to 8, avoids (2401.7

– 2451.5)MHz. When set to 9, avoids (2429.3 – 2479.1)MHz. When set to A, avoids

(2401.7 – 2429.3)MHz and (2458.8 – 2479.1)MHz. If the WIT2450 is to be used in close

proximity to 802.11b networks, these alternative hopsets can be used to avoid interfering

with the 802.11b networks.

Note: This parameter affects the setting of wn (Hopping Pattern).

Set Hop Duration

Sets the length of time the transceiver spends on each frequency channel. A smaller

value will allow the remote to lock on to the base signal faster at system startup, and will

generally decrease packet latency. A larger value increases network capacity, due to

decreased overhead in channel switching. The hop duration is specified in 69.4µs

increments. The default value of 90H corresponds to a duration of 10ms. The maximum

value of FEH is 17.627ms. For best results, do not specify a duration of less than 3 ms.

This value only needs to be set in the base which broadcasts the parameter to all remotes.

However, link time can be reduced if this value is also programmed into the remotes,

which use it as a starting value when scanning for the base.

Set Minimum Data Length

This sets the minimum threshold number of bytes required to form a packet in transparent

mode. The radio will wait until the data transmit delay elapses before sending a data

packet with less than this number of bytes. Can be used to keep short, intermittent

transmissions contiguous. In packet modes, the length parameter in the data packet will

override this value (See Section 3.1). This value is subject to the maximum data length

even in packet mode. See Get Maximum Data Length below.

Get Maximum Data Length (remote only, read only)

This parameter indicates the largest number of bytes that a remote will transmit per hop,

based on the size of the slot it has been allocated by the base. In general more remotes

mean less data can be transmitted per remote. By reading this parameter and dividing by

the hop duration, the remote's data rate capacity can be determined. Attempting to send

protocol mode packets longer than maximum data length will result in the packet be ing

discarded without being sent. See Section 2.3.3 on the tradeoffs between hop duration

and data length.

WIT2450

Set Maximum Number of Remotes (base only)

This parameter limits the number of remotes that can register with a given base. The

default is 62 remotes which is the maximum number of remotes that can be registered

with a base at one time. This command is useful when used in conjunction with global

roaming for load balancing when base stations are collocated. It is also useful to assure a

minimum remote throughput.

Set Packet Attempts Limit

If ARQ Mode is set to 0, sets the number of times the radio will attempt to send an

unsuccessful transmission before discarding it. If ARQ Mode is set to 1, it is the number

of times every transmission will be sent, regardless of success or failure of a given

attempt. When this parameter is set to FFH, RF flow control mode is entered for

transmissions from the radio (See Section 2.3.4). This mode can be entered for one or

both radios in a point-to-point system. When used in a point-to-point system the wu

parameter should be set to 1. Using this mode in a point-to-multipoint system will stop

transmissions to all radios when any one radio has a full buffer or if the base radio

attempts to send data to a remote that has recently (<2.5 seconds) left the range of the

base.

Set Data Transmit Delay

When used in conjunction with the minimum data length parameter, this sets the amount

of time from the receipt of a first byte of data from the host until the radio will transmit in

transparent mode. Default is 00H which causes transmission to occur without any delay.

When a host is sending a group of data that needs to be sent together, setting this

parameter will provide time for the group of data to be sent by the host before the radio

transmits. If the length of data to be sent together is longer than the time slot can send,

the data will not be sent together but will be broken up over multiple hops. The length of

time the radio will wait is equal to the specified value times the hop duration.

Set Slot Assignment Mode (base station only)

Sets whether the base station will assign remote transmit slots dynamically, based on the

number of remotes currently registered or whether the base station will assign remote

transmit slots statically, based on the maximum number of remotes parameter. If static

slot assignment is selected, make sure maximum number of remotes is correctly set.

Otherwise remote transmit performance will suffer as transmit time will be reserved for

remotes that may not exist. The dynamic assignment mode will generally be preferred;

however, the static assignment mode will result in a static maximum data length

parameter.

Set Base Slot Size (base station only)

Sets the amount of time allocated for transmission on each hop for the base station time

slot in 69.4µs increments, corresponding to 4 bytes per unit. Maximum value is 34H

which corresponds to 208 bytes. If using a protocol mode, attempting to send a packet

with a length longer than this setting will cause the packet to be discarded.

WIT2450

Set ARQ Mode

Sets ARQ mode when set to 0 which is the default. In this mode the radio will resend an

unsuccessful transmission until eith er successful or packet attempt limit attem pts have

been made. When set to 1 selects redundant transmit mode that will send every

transmission packet attempt limit times regardless of success or failure of any given

attempt. When redundant transmit mode is used, receiving radios will discard all

subsequent retransmissions once the transmission has been successfully received. Thus

the receiving host will receive just one copy of the transmission.

5.4. Status Commands

These commands deal with general interface aspects of the operation of the WIT2450.

Command Description

zb[?|0|1]

Banner Display Disable

0 = disabled

1 = enabled (default)

zc[?|0..2]

Set Escape Sequence Mode

0 = disabled

1 = once after reset (default)

2 = unlimited times

zh? Read factory serial number high byte.

zm? Read factory serial number middle byte.

zl? Read factory serial number low byte.

zp[?|0-4] Set the duty cycle at which the modem will wake up to send and receive data.

Duty cycle equals 1/2N where the argument of the command equals N.

Default is zp = 0

zq[?|0|1]

(remote only)

Low Power Acquisition Mode Enable

0 = Disabled (default)

1 = Enabled

Exit Modem Control Mode

Banner Display Disable

Enables or disables display of the banner string and revision code automatically at power-

up. May be disabled to avoid being mistaken for data by the host.

Set Escape Sequence Mode

Enables or disables the ability to use the in-data-stream escape sequence method of

accessing Control Mode by transmitting the string ":wit2410". When this mode is set

to 1, the escape sequence only works immediately after reset (this is the default). When

set to 2, the escape sequence may be used at any time in the data stream when preceded

by a pause of 20 ms. For backwards compatibility with the WIT2400, the string

":wit2400" is also accepted for entering Control Mode. Note that the escape sequence

WIT2450

must be interpreted as data by the radio until the last character is received, and as such

will be generally be transmitted to a receiving radio station, if any.

Read Factory Serial Number High, Middle and Low Bytes.

These read only commands return one of the three bytes of the unique factory-set serial

number, which are also visible in the startup banner.

Set Duty Cycle

Allows reduced power consumption by having a remote wake up only every 2N hops to

receive and transmit.

Enable Low Power Acquisition Mode. When a remote is searching for a base to acquire

and register with, it scans the frequency band very rapidly and consumes more current.

To reduce the frequency consumption when a remote is in acquisition mode, a low power

acquisition mode is provided. In this mode, the remote only scans the frequency band

every other hop. This will cut the average current consum ption during acquisition in half.

The tradeoff is it can take twice as long to acquire and register with a base although

typically less than 4 seconds.

5.5. Memory Commands

The WIT2450 allows the user to store a configuration in nonvolatile memory, which is

loaded during the initialization period every time the radio is powered up. Note that

changes to the serial port baud rate from recalling the factory defaults or recalling

memory will not take effect until DTR is toggled or power to the radio is cycled.

Command Description

Recall Factory Defaults

Recall Memory

Store Memory

m! Display Modified Parameters

Recall Factory Defaults

Resets the WIT2450 to its factory default state. This is useful for testing purposes or if

there is a problem in operation of the system and the configuration is suspect. Use the

Store Memory command afterwards if you wish the factory default settings to be

remembered the next tim e you cycle power or reset the radio.

Recall Memory

Useful for restoring the power-on settings after experimenting with temporary changes to

data rate, protocol or network parameters, etc.

Store Memory

This command is necessary after any command to change the data rate, transceiver

address, or other radio setting that you wish to make permanent.

WIT2450

Display Modified Parameters

This command lists all parameter settings that are different from the factory default

settings. This will list changed parameters whether or not they have been stored with the

m> command. Note that issuing this command will cause the radio to lose link with the

base and will cause all remotes to lose link when issued to the base radio.

WIT2450

5.6. Modem Command Summary

Serial Commands

sd[?|00..ff] Set Data Rate Divisor

sp[?|00..14] Set Protocol Mode

Network Commands

wb[?|0|1] Set Transceiver Mode

wd[?|00..3f] Set Default Handle

wl[?|00..ff] Set Lockout Key

wn[?|00..3f] Set Hopping Pattern

wg[?|0|1|2] Enable Global Network Modes

wp[?|0|1|2] Set Transmit Power

wr? Read Receive Signal Strength (remote only)

wu[?|0|1] Set Point-to-Point Direct Mode

Protocol Commands

pe[?|0..B] Set Alternative Frequency Band

ph[?|00..fe] Set Hop Duration (base only)

pl? Get Maximum Data Length (remote only, read only)

pn[?|01..3e] Set Maximum Number of Remotes (base only)

pk[?|00..d4] Set Minimum Data Length

pr[?|00..ff] Set Packet Attempts Limit

pt[?|00..ff] Set Data Transmit Delay (remote only)

pv[?|0|1] Set Slot Assignment Mode (base only)

pw[?|00..2f] Set Base Slot Size (base only)

px[?|0|1] Set ARQ Mode

Status Commands

zb[?|0|1] Banner Display Disable

zc[?|0..2] Set Escape Sequence Mode

zh? Read Factory Serial Number High Byte

zm? Read Factory Serial Number Middle Byte

zl? Read Factory Serial Number Low Byte

zp[?|0..4] Set Duty Cycle

zq[?|0|1] Enable Low Power Acquisition (remote only)

z> Exit Modem Control Mode

Memory Commands

m0 Recall Factory Defaults

m< Recall Memory

m> Store Memory

m! Display Changed Parameters

Note: Brackets ([,]) as used here denote a set of option al arguments. Vertical slashes separate selections.

For example, given the string wn[?|00..3f], legal commands would be wn?, wn0, wn3, and wn2a.

Most commands which set a parameter also have a ? option which displays the current parameter setting;

e.g., wn?.

WIT2450

6. WIT2450 DEVELOPER’S KIT

The WIT2450 Developer’s Kit contains two self-contained wireless modems (HN-550s)

built around the WIT2450 OEM module. In addition, two WIT2450 OEM modules are

included in the kit. The self-contained units allow developers to get up and running

quickly using standard RS-232 interfaces without having to build a CMOS level serial

interface. In addition, the self-contained modems include status LEDs to provide modem

status information visually. The built-in battery pack allows the developer to use the

modems without being tethered to a power source. This provides a simple way to test the

range of the radios. Other than the true RS-232 signals of the serial interface, the self-

contained modems operate exactly as the OEM modules.

Connection is made to the HN-550s through a standard DB-9 connector. The HN-550s

are set up as DCE devices requiring the use of a straight-through cable to connect to DTE

devices. The pinout is provided in Section 7.2. The modems can be used with just a

three wire connection. Transmit data, receive data and ground are the three required

connections. Note that in this configuration, no flow control is available as the WIT2450

does not support software flow control.

When the developer’s kit is shipped from the factory, one HN-550 is set up as a base

station and the other is set up as a remote. The interface rate for both modems is set at

9600 bps. The default setting for the network key allows the modems to communicate

without changing any settings. As a quick test, separate the two modems by about 5 feet,

plug in the power and turn the modems on. Do not connect the modems to any device.

The Carrier Detect (CD) LED on the base station will come on immediately. After a few

seconds, the CD LED on the remote will come on. This indicates that the modems have

synchronized and have established a communications link.

An important point to remember is that if the base station is in Sleep mode, no

communications can take place until (1) the base station is taken out of sleep mode and

(2) the remote has synchronized with the base station. As the Sleep signal is brought out

on the pin usually occupied by DTR, connecting the base station to a PC serial port with

DTR de-asserted will put the modem into sleep mode. Some communications programs

will attempt to communicate immediately after asserting DTR. The base station will

transmit this data, but the remote will not be synchronized with the base station and will

not receive the transmission. In this instance, do not connect the Sleep signal to DTR of

the serial port.

WIT2450

7. WinCOM

Provided with the developer’s kit is a configuration program designed especially for

Cirronet’s wireless industrial transceivers or WIT radios. WinCOM is located on the

Manuals and Software CD included in the developer’s kit. Install WinCOM by

navigating to the Software Tools directory on the Manuals and Software CD and double-

click on wincom2.1.exe follow the installation wizard. Once it has installed, open

WinCOM by double-clicking on the WinCOM icon on the desktop.

WIT2450

WinCom’s menu structure is typical of Windows conventions with File, Edit, Options,

Tools and Help selections.

Under File, Save Settings (Ctrl S) saves the current

WinCom settings to the hard drive, Print (Ctrl P)

sends whatever text is in the display field to the

printer and Exit terminates the program.

Under Edit, Copy, Paste, Find (search) and Select

All perform the familiar Windows functionality in

typical fashion.

The Options menu contains the selections, Show

Comm Errors which lists any errors encountered in

the PC UART. Check Comm Ports on Bootup tells

WinCom to verify each available port and lists

them as such in the Com Port drop down field.

See the section entitled WinCom Tools for an

explanation of this drop down.

The Help menu displays the About screen which

lists the version number, hardware and software

information for the system being used.

WIT2450

7.1. Starting the program

When started, WinCOM de-asserts and re-asserts the DTR line to the radio which resets

the radio causing the sign-on banner to be displayed. If the baud rate on the computer

doesn’t match the baud rate of the radio, illegib le characters will be displayed. By hitting

the PgUp or PgDn key to change the baud rate, then pressing F1 twice to toggle DTR

(resets the radio) and causes a new banner to be displayed. Continue changing baud rates

in this fashion until a legible banner is displayed as shown below.

The banner indicates the radio firmware version, whether the radio is operating as a base

or a remote and the unique factory serial number of the radio module. If nothing is

displayed in the communications window of WinCOM, verify the COM port and baud

rate settings, then reset the radio (by hitting F1 twice). Cycling power to the radio also

will cause the sign on banner to be displayed unless the banner is disabled via the Banner

Display Disable command (zb0).

The COM port and baud rate can be changed using the drop down menus on the bottom

right. All the available COM ports will be listed in the menu but will have OK or N/A

designated. If another program that uses a COM port is open, that COM port will not be

available for use by WinCOM.

The boxes on the lower right of the WinCOM window provide the status of the COM

port flow control being used to communicate with the radio. Note that DCD is only

asserted by radios configured as remotes when they are linked to a base radio. Radios

configured as bases always assert DCD even if no remotes are linked. Clicking on the

DTR or RTS buttons will change the state of the respective signal line in the COM port.

The radio is normally in data mode – data that is sent to it from the PC is transmitted over

the wireless connection. When the WinCOM window is active, keys typed on the

keyboard will be sent to the radio and will be transmitted. Unless the “Echo” box is

checked the typed data will not be displayed in the WinCOM window of the sending

radio.

WIT2450

To change configuration parameters, the radio must be put into configuration mode by

clicking on the Config Mode button on the WinCOM window immediately after opening

WinCOM or after cycling power to the radio. Another method is to toggle the DTR by

pressing the F1 key twice, which de-asserts then re-asserts DTR, then pressing the F3 key

(or Config Mode button).

When the radio is in configuration mode, a “>” prompt character is displayed in the

WinCom window as shown above. Configuration parameters are sent to the radio by

entering them in the WinCom window after the “>” prompt and pressing the Enter key.

If an invalid command or value is entered, the radio will resp ond with “Error” as shown

above Until the command to save the parameters (m>) is issued, the new parameters will

only be valid until power is cycled or DTR is toggled by pressing the F1 key twice.

New parameter values that have been issued are saved to non-volatile memory using the

“m>” command. Refer to the Memory Commands section for details on this and other

helpful memory commands.

To exit configuration mode from the WinCom screen, use the “z>” command and press

Enter as shown below.

The return to the data mode is indicated by an absence of the “>” prompt. Refer to the

Configuration Commands section below for details on all the configurable parameters.

When the radio is linked to another radio, a communications test can be run by clicking

on the Transmit button or pressing the F6 key. Whatever ASCII string is in the Transmit

String window will be transmitted as shown below.

WIT2450

If the other radio is sending data, the received data will be displayed in the WinCOM

window.

If the Binary box is checked, all characters received will be displayed subject to the

limitations of Windows. For example, a carriage return will not return the cursor to the

left side of the window but the character corresponding to 0xd value of the carriage return

will be displayed. Similarly, if the Hex Mode box is checked, all characters are displayed

in hexadecimal format.

The Clear Screen button deletes all the text in the display window. The Clear CTS and

Clear DCD buttons reset the respective changes counters to zero.

WIT2450

After naming the file and clicking on OK, the Capture Data window opens and shows the

amount of data being received. Clicking on Done stops the loading of received data into

the file.

7.2. Function Keys

All of the function key shortcuts are described below:

F1 Toggles state of DTR (Sleep). State is shown in status line.

F2 Toggles state of RTS. State is shown in status line.

F3 Transmits “:wit2400”. Used to enter control mode.

F5 Toggles local echo. If you are transmitting characters through one modem

to another WIT2450, this allows you to see what you are typing.

F6 Toggles stream mode. Causes WinCOM to transmit a repeating pattern of

characters. Useful for testing.

F8 Toggles binary mode. Displays extended ASCII and control characters.

Useful for testing.

PgUp Sets data rate of PC serial port to next higher value. Value is displayed in

status line. Useful when WinCOM is used to change the WIT2450

interface data rate. WinCOM can communicate at new data rate without

having to exit and re-enter WinCOM.

PgDn Sets data rate of PC serial port to next lower value. Value is displayed in

status line.

WIT2450

7.3. WinCom Tools

There are seven selections under the Tools menu. The first, Obey CTS is useful when just

a three wire connection is made between the radio and the computer. Some PCs let the

CTS input line float. If CTS is not asserted, the PC COM port will not send data.

Note: Unchecking this selection will have the PC COM port

ignore the state of CTS and transmit data.

When WinCOM’s transmit mode is used, data is sent continuously until the user stops it

by clicking on Stop or pressing F6. If the second tool, Single Transmit, is checked,

clicking the Transmit button will send the Tr ansmit String a single tim e. There is no need

to click Stop. Clicking on the Transmit button a second time will have the string

transmitted a second time.

The third allows for checking of available Comm Ports and is useful for refreshing the

list.

The fourth, Transmit Tools allows for testing of the Transparent, WIT2410/WIT910 or

WIT2411 settings. Parameters related to how the transmission will take place can be set

including Handle, Transmit Period, whether or not a Sequence Number should be added,

if the Transmission will be continuous or one time, if the data should be sent in Hex

Format and whether or not data can be received. Data is entered into the Data f ield, then

Data Size can be set and clicking Fill loads the data into the Transmit Field.

WIT2450

The Packet Builder is an easy way to test the multipoint addressing mode of the

WIT241x radio. Since the WIT241x operates in a star configuration in multipoint mode,

only the base radio needs to address data to specific remotes. All remotes send data back

to the base and do not need to address the data to the base. To send a packet of data to a

specific remote in a multipoint network, enter the handle of the desired remote in the

Handle window. Type whatever data to be transmitted in the Data to Transmit window.

In the bottom window, you will see the entire packet being built as the da ta is entered in

the windows. When all the data has been entered, click on the Transmit button to send the

data.

WinCOM has the ability to perform any function or sequence of functions WinCOM can

perform through a script file. A script file is a text file that contains one or more

commands and arguments save with a wcr filename extension. Each command is

separated by a carriage return and linefeed. Configuration commands need to have wait

periods between them. The list of commands and their definitions is below:

WIT2450

7.4. Script Commands

cp <arg> Selects the COM port to use

br <arg> Selects the baud rate to use

do Asserts DTR

df De-asserts DTR

ro Asserts RTS

rf De-asserts RTS

cm Sends configuration escape sequence

oo Obey CTS/RTS

of Do not obey CTS/RTS

sc <cmd(arg)> Send WIT910 format configuration command

wt <arg> Pause for arg milliseconds

An example script file is shown below:

br 115200

wt 200

sc m!

This script file sets the baud rate of the PC COM that WinCOM is using to 115,200 kbps,

de-asserts DTR, waits 200 milliseconds, asserts DTR, waits 200 milliseconds, sends the

configuration mode escape sequence, waits 200 milliseconds and then sends the m!

command to the radio. What this script file does is set the PC COM port baud rate to

115.2 kbps, puts the radio in config mode and the issues the command to display all of

the radio parameters that have been changed from factory default. Note that this script

file leaves the radio in config mode. Cycling power or toggling DTR will return the radio

to data mode.

WinCOM prompts you to select the desired .wcr file. Opening the script file causes it to

executed immediately.

WIT2450

The seventh tool allows the loading of a data file for transmission. Navigate to a file then

click Open and the file is transmitted immediately.

The Capture File dialog displays with a bar showing loading progression. Once the file

has finished transmitting, the Final Average Throughput and Bytes sent numbers will be

displayed.

Finally, the eighth tool is Save to File which launches a Save As dialog that allows any

data received to be loaded into a file.

WIT2450

7.5. Demonstration Procedure

The procedure below provides a quick demonstration of the WIT241x.

1. Attach a transceiver to each computer, preferably between 5' and 30' apart for

convenience.

2. Start WinCOM running on both computers If you prefer, almost any other serial

communications program such as Procomm or QModem set for 9600 bps will

also work.

3. Turn the radios on and use the function keys to set DTR and RTS to 1 (if you are

using a terminal program other than COM24, these are typically set

automatically). The radio should respond by setting both DSR and CTS to 1, and

transmit a short sign-on message including the firmware version and whether the

unit is configured as a base or remote. Watch the states of th e hardware control

lines on the status bar as you do this. The DCD indicator should be lit on the base

station. After a few seconds, the remote unit will acquire the base station's signal

and also assert its DCD signal.

4. Access modem control mode for each unit. To access modem control mode, use

the F1 key to toggle DTR to 0 and back to 1 and then press the F3 key, which

sends the ":wit2400" escape sequence. If you are not using COM24, simply turn

the radio off and back on and then type ":wit2400" (must be lower case, no

backspace characters). The transceiver should echo back “>” to indicate that you

have entered modem control mode. Check the remote unit's hopping pattern by

entering "wn?" at the prompt. The remote should respond with "0", the default

setting. Check that the base station's hopping pattern matches this by entering

"wn?" at the base station.

5. Exit control mode by entering "z>". Do this for both radios. At this point, you

should be able to type characters into either radio and see them appear at the other

side. If you are using WinCOM, you can press the F6 key to transmit a repeating

test pattern.

6. For a range test, disconnect the remote station from the computer and power

supply. The DCD indicator should remain lit as long as the base station is in

range..

7. Exit COM24 by pressing the ESC key.

WIT2450

8. Troubleshooting

Radio is not responding.

Make sure DTR is asserted to bring the radio out of sleep mode. DSR should be on to

indicate the radio is ready.

Can’t enter modem control mode.

Make sure the host data rate is correct. The WIT2450 defaults to 9600 bps asynchronous.

Evaluation units do not have external access to the CFG_SEL signal; you must use the

:wit2410 power-on escape sequence to access modem control mode. The first characters

typed after the radio wakes up should be the escape sequence. Make sure you type the

colon (:) and enter the letters in lower case; the characters following the colon echo to

show you have typed them correctly. If using the “on-the-fly” escape sequence

command, make sure a pause of at least 20ms precedes the escape sequence.

Remote never detects carrier.

Check that the base station is running, and that the remote is programmed to the same

hopping pattern. Also check that the hop duration for base and remote are the same, and

that the remote has a non-zero link margin.

Carrier is detected, but no data appears to be received.

Make sure that RTS is asserted to enable receive character flow. In a poin t-to-point

application, if a remote is not receiving data, check that the base's default handle is the

same as the remote's. In a multipoint application, check that the remote is not configured

for protocol mode and that the base is using the correct protocol format and destination

handle.

Radio is interfering with other nearby circuits.

It is possible for the RF energy envelope to be rectified by nearby circuits that are not

shielded for RFI, manifesting as a lower frequency noise signal. If possible, place the

antenna at least 1 foot away from the transceiver module, and 3 feet from other circuit

boards and obstructions. Place sensitive circuits in a grounded metal casing to keep out

RFI.

Sign-on banner or modem control mode prompt is unreadable.

If the problem is repeatable, check whether the data rates between host and transceiver

match.

Range is extremely limited.

This is usually a sign of poor antenna coupling. Check that the antenna is firmly

connected. If possible, remove any obstructions in the near field of the antenna (~3'

radius).

Transmitting terminal flashes CTS occasionally.

WIT2450

This indicates that the transmitter is unable to reliably get its data across. This m ay be

the result of an interfering signal, but most often is caused by overloading of the network.

Adjusting the protocol parameters may increase the network efficiency.

Receiving terminal drops characters periodically.

Set the number of retries to a high number and send a few characters. Check that the

transmitted data can get through under these conditions. Sometimes this symptom is

caused by an application that is explicitly dependent on the timing of the received data

stream. The nature of the packetized RF channel imposes a degree of unpredictability in

the end-to-end transmission delay.

Cannot communicate with the OEM module.

Make sure DTR and RTS are asserted. DSR should be on to indicate the radio is ready.

OEM Module is in an unknown state.

Use the m0 command to restore the factory defaults. Note that the serial baud rate must

be set correctly for the module to receive this command.

WIT2450

9. APPENDICES

9.1. Technical Specifications

9.1.1. Ordering Information

WIT2450M

9.1.2. Power Specifications

Vcc Input Range: 3.3v to 10.0v

Operating Temperature Range: -40°C to +70°C

Current Consumption (Max transmit power @ 5Vcc, 230.4Kbps I/O)

Mode Remote Base Station

Power Down .75 mA N/A

Receive 40 mA N/A

Typical Average 55 mA 155 mA

Peak (Tx) 150 mA 155 mA

9.1.3. RF Specifications

FCC Certification Part 15.247, no license required

ETSI (European) Certification brETSI 300.328, no license required

Rated RF Power +24 dBm

Line-of-site Range approx. 6/10 of a mile w/2dB dipole

Frequency Range 2401 – 2495MHz

Number of Channels 95 US

Receiver Sensitivity -92dBm @ 10-5 BER

Channel Data Rate 460Kbps

IF Adjacent Channel Rejection >55dB

9.1.4. Mechanical Specifications

Weight 28g

Dimensions (incl. shield) 69.85 x 47.75 x 4.57mm

(refer to section 7.6 for mechanical drawing)

RF Connector:

WIT Huber/Suhner: 82 MMCX S50-0-2

Mating Huber/Suhner: 11 MMCX-50-2-3

(straight)

Huber/Suhner: 16 MMCX-50-2-2 (rt. angle)

Data/Power Connector:

WIT Samtec: SAMTEC CLT-108-02-G-D

Mating Samtec: SAMTEC MTMM-108-05-G-D-300

(PCB mount)

WIT2450

9.2. Serial Connector Pinouts

Signal

WIT2450

OEM Pinout

HN-550

DB9

Pinout

GND 1 5

TXD 2 3

RXD 3 2

CFG 4 -

RTS 5 7

DTR 6 4

DCD 7 1

CTS 8 8

The HN-550 is wired as a DCE device and as such can be connected to DTE devices such

as PCs with a straight-through cable. When connecting a HN-550 to a D TE device, a

“null modem” cable is required. To effect a null modem cable, cross-wire TXD and

RXD and connect ground. The HN-550 can operate with just these three wires

connected. However, as the WIT2450 does not support software flow control, there will

be no flow control in this mode. If the DTE device fails to respond, connect DCD from

the HN-510 to the DTR and RTS inputs to activate the DCE device whenever the

WIT2450 asserts carrier.

When connecting to the WIT2450, make sure that all of the inputs (TXD, CFG, RTS and

SLEEP) are terminated for proper operation.

9.3. Approved Antennas

The WIT2450 is designed to ensure that no antenna other than the one fitted shall be used

with the device. The end user must permanently affix the antenna by using an adhesive

on the coupling such as Loctite, or ensure the antenna has a unique coupling. The table

below lists the antennas which can be purchased directly from Cirronet. Contact Cirronet

Technical Support with any questions.

Description Gain Part Number Coupling

24dB Parabolic Dish 24dB PAR2424 N

18dB Parabolic Dish 18dB PAR2418 N

15dB Yagi Directional 15dB YAGI2415 N

14dB Corner Refle ctor 14dB CORNER2414 N

12dB Omnidirectional 12dB OMNI2412 N

9dB Omnidirectional 9dB OMNI249 N

9dB Corner Reflector 9dB CO RNER249 N

6dB Cironnet Patch 6dB PA2400 MMCX

5dB Mobile Mount 5dB MAG245 N

2dB Cirronet Patch 2dB PA2410 MMCX

2dB Rugged Body Mount 2dB RBM242 N

Dipole 2dB RWA249R Reverse SMA

WIT2450

9.4. Technical Support

For technical support call Cirronet at (678) 684-2000 between the hours of 8:30AM and

5:30PM Eastern Time.

WIT2450

9.5. Reference Design

WIT2450

9.6. Mechanical Drawing – WIT2450

WIT2450

10. Warranty

Seller warrants solely to Buyer that the goods delivered hereunder shall be free from

defects in materials and workmanship, when given normal, proper and intended usage, for

twelve (12) months from the date of delivery to Buyer. Seller agrees to repair or replace at

its option and without cost to Buyer all defective goods sold hereunder, provided that

Buyer has given Seller written notice of such warranty claim within such warranty period.

All goods returned to Seller for repair or replacement must be sent freight prepaid to

Seller’s plant, provided that Buyer first obtain from Seller a Return Goods Authorization

before any such return. Seller shall have no obligation to make repairs or replacements

which are required by normal wear and tear, or which result, in whole or in part, from

catastrophe, fault or negligence of Buyer, or from improper or unauthorized use of the

goods, or use of the goods in a manner for which they are not designed, or by causes

external to the goods such as, but not limited to, power failure. No suit or action shall be

brought against Seller more than twelve (12) months after the related cause of action has

occurred. Buyer has not relied and shall not rely on any oral representation regarding the

goods sold hereunder, and any oral representation shall not bind Seller and shall not be a

part of any warranty.

THE PROVISIONS OF THE FOREGOING WARRANTY ARE IN LIEU OF ANY

OTHER WARRANTY, WHETHER EXPRESS OR IMPLIED, WRITTEN OR

ORAL (INCLUDING ANY WARRANTY OR MERCHANT ABILITY OR

FITNESS FOR A PARTICULAR PURPOSE). SELLER’S LIABILITY ARISING

OUT OF THE MANUFACTURE, SALE OR SUPPLYING OF THE GOODS OR

THEIR USE OR DISPOSITION, WHETHER BASED UPON WARRANTY,

CONTRACT, TORT OR OTHERWISE, SHALL NOT EXCEED THE ACTUAL

PURCHASE PRICE PAID BY BUYER FOR THE GOODS. IN NO EVENT

SHALL SELLER BE LIABLE TO BUYER OR ANY OTHER PERSON OR

ENTITY FOR SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES,

INCLUDING, BUT NOT LIMITED TO, LOSS OF PROFITS, LOSS OF DATA OR

LOSS OF USE DAMAGES ARISING OUT OF THE MANUFACTURE, SALE OR

SUPPLYING OF THE GOODS. THE FOREGOING WARRANTY EXTENDS TO

BUYER ONLY AND SHALL NOT BE APPLICABLE TO ANY OTHER PERSON

OR ENTITY INCLUDING, WITHOUT LIMITATION, CUSTOMERS OF

BUYERS.