WIT2411D - RFM - Datasheet.Directory

WIT2411

2.4GHz Spread Spectrum Wireless Industrial Transceiver

Integration Guide

Important Regulatory Information

Cirronet Product FCC ID: HSW-2411

IC 4492A-2411

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 e xpo sure limits

may be exceeded if personnel com e 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 WIT2411 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

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 ......................................................................................................................1

1.1. Why Spread Spectrum? ........................................................................................................1

1.2. Frequency Hopping vs. Direct Sequence..............................................................................2

2. RADIO OPERATION................................................................................................................5

2.1. Synchronization and Registration........................................................................................5

2.2. Data Transmission ...............................................................................................................6

2.2.1. Point-to-Point.............................................................................................................6

2.2.2. Point-to-Multipoint ....................................................................................................7

2.2.3. Handle Assignment....................................................................................................7

2.2.4. TDMA Operation.......................................................................................................8

2.2.5. Full Duplex Communication....................................................................................10

2.2.6. Error-free Packet Transmission Using ARQ............................................................10

2.3. Modes of Operation...........................................................................................................12

2.3.1. Control and Data Modes ..........................................................................................12

2.3.2. Sleep Mode ..............................................................................................................12

2.3.4. RF Flow Control Mode............................................................................................13

3. PROTOCOL MODES ..............................................................................................................14

3.1.3. Connect Packet.........................................................................................................16

3.1.4. Disconnect Packet (base only, receive only) ..........................................................16

4. MODEM INTERFACE............................................................................................................17

4.1. Interfacing to 5 Volt Systems ............................................................................................18

4.2. Evaluation Unit and Module Differences..........................................................................18

4.3. Three-Wire Operation........................................................................................................18

5. MODEM COMMANDS...........................................................................................................19

5.1. Serial Commands...............................................................................................................19

5.2. Network Commands..........................................................................................................20

5.3. Protocol Commands...........................................................................................................21

5.4. Status Commands ..............................................................................................................23

5.5. Memory Commands ..........................................................................................................24

5.6. Modem Command Summary.............................................................................................25

6. WIT2411 DEVELOPER’S KIT ...............................................................................................26

7. WinCOM...................................................................................................................................28

7.1. Starting the program ..........................................................................................................30

7.2. Function Keys....................................................................................................................33

7.3. WinCom Tools...................................................................................................................34

7.4. Script Commands...............................................................................................................36

7.5. Demonstration Procedure ..................................................................................................38

8. Troubleshooting........................................................................................................................39

9. APPENDICES ..........................................................................................................................41

9.1. Technical Specifications....................................................................................................41

9.1.1. Ordering Information...............................................................................................41

9.1.2. Power Specifications................................................................................................41

9.1.3. RF Specifications.....................................................................................................41

9.1.4. Mechanical Specifications .......................................................................................41

9.2. Serial Connector Pinout.....................................................................................................42

9.3. Approved Antennas ...........................................................................................................42

9.4. Technical Support..............................................................................................................43

9.5. Reference Design...............................................................................................................44

9.6. Mechanical Drawing – WIT2411D ...................................................................................45

10. Warranty .................................................................................................................................46

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1. INTRODUCTION

The WIT2411 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 921600 bps. An on-board 12 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 43 frequency channels

(2401-2475 MHz).

- Supports point-to-point or

multipoint applications.

- Meets FCC rules 15.247 and ETS

300.328 for worldwide license-

free operation.

- Superior range to 802.11 wireless

LAN devices.

- Transparent ARQ protocol

w/12KB buffer ensures data

integrity.

- Digital addressing supports up to

64 networks, with 62 remotes per

network.

- Low power 3.3v CMOS signals

- Fast acquisition typically locks

to hopping pattern in 2 seconds

or less.

- Selectable 8 mW or 18 mW

transmit power.

- Built-in data scrambling reduces

possibility of eavesdropping.

- Nonvolatile memory stores

configuration when powered

off.

- Smart power management

features for low current

consumption.

- Dynamic TDMA slot

assignment that maximizes

throughput.

Simple serial interface handles

both data and control at 115,200

or 921600 bps.

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

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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

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.

WIT2411

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

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.

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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.

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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 up to 43 frequencies and the rem o te is

scanning up to 43 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 automatically changed are hop

duration and hop set.

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. The

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

size parameter. If there is no data to be sent, the base station will not tran smit data until

the next frequency.

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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 remotes currently transmitting data. A detailed

explanation of this relationship is provided in Section 2.2.3.

Except for the registration process that 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 WIT2411 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, the base station will transmit whatever data is in its buff er limited

to 65,536 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 it’s transmit slot or slots. 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 address, a packet sequence

number and 24-bit CRC. These additional bytes are transparent to the user application if

the protocol mode is 00 (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.

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The WIT2411 has a point-to-point direct mode which fixes the remote radio’s handle at

30H. 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 the section

on 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.

If the remote device can determine if a particular transmission is intended for it (e.g. there

is addressing information contained in the data payload), broadcast mode can be used. In

this mode, the default handle is set to a value of 63 (3FH). In broadcast mode, all remotes

will receive all transmissions and thus it is up to the remote device to determine for which

device a particular transmission is intended. In this mode, ARQ retries becomes a

redundant transmit count, that is, the number of times the base radio will broadcast each

transmission. This is provided since the ARQ mechanism must be disabled in broadcast

mode. Once a remote radio has successfully received a transmission from the base, any

subsequent transmissions of the same data is discarded by the remote radio. So just one

copy of each transmission will be transmitted to the remote device by the rem o te radio.

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.

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When a remote links to a base and requests registration, it is assigned an unused handle

by the base. If the remote is the only or first radio registering with the base, it will be

assigned handle 30H. 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 30msec per hop, this could be as along as 7.65 seconds. If within this time the

remote re-establishes link with the base, the previous handle assigned to this rem o te will

still be marked active in the base radio. Thus the remo te w ill 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

In the WIT2411 TDMA scheme, the base station time slot is set independently of the

remote time slots through the Set Base Slot Size command. The base divides the time

remaining in the hop after subtracting for the base overhead, base slot size and guard

bands between remote transmit slots into 26 equal-size remote transmit slots. These 26

transmit slots are allocated among remotes requesting transmit slots. Each remote that has

data to send requests a transmit slot from the base radio. Based on the amount of data the

remote has to send, the remote will request more or fewer transmit slots. Depending on

the number of unused remote-to-base transmit slots, the base radio either will assign one

or more slots or will not assign a slot. The remote will request slots on every hop that it

has data to send. When it has no data to send, it indicates that to the base and any slots

that have been assigned are freed for assignment to other remotes. Depending on the

amount of activity of other remotes, the number of transmit slots assigned to a remote can

vary from hop to hop even if the number requested does not change.

A typical sequence goes as follows: Data is sent to a remote radio by the remote host.

During a contention time in the hop, the remote requests some number of transmit slots

based on the amount of data it has to send. Up to three remotes can request time slots

during a single contention period. On the next hop, the base radio assigns some transmit

slots to the remote. On that same hop, the remo te transmits as much data as will fit in the

assigned time slots and request time slots for the next hop. The requests for time slots by

remotes currently assigned time slots do not occur in the contention period and thus do

not count against the three remotes that can request slots during this period. On the hop

when the remote exhausts the data it has to send, the remote indicates to the base that it

has no data to send. The base adds those slots back into the pool of unused slots. There

are a total of 26 remote to base transmit slots. Thus a maximum of 26 remotes can be

transmitting to the base on a single hop with each remote assigned a single slot. Remotes

will be assigned as many slots as are available up to the number requested by the remote.

A remote can request a maximum of 26 slots. The number of slots requested by a remote

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is calculated by the remote based on the amount of data it has to send. The calculation is

performed to send the data in as few hops as possible.

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.

The base station requires 1.7 ms overhead for tuning, the synchronization signal and

parameter updating, as well as a guard time of 150µs between each remote slot. Thus the

amount of time allocated per remote slot is roughly:

hop duration – base slot – 1.7ms – 25 transmit slot guard bands·150µs

26 remote transmit slots

For the default settings of base slot size of 160H and hop duration of 240H, the amount of

data that can be transmitted by remotes per hop is calculated by:

The hop duration is set in 52.1µsec increments. Thus a hop duration of 240H becomes:

576 x 52.1µsec = 30msec

The base slot size is set in increments of 8 bytes. A base slot size of 160H is:

160H = 352 Decimal x 8bytes = 2,816 bytes

With a 1,228,800 bps data rate, the time it takes to transmit 2,816 bytes of data is:

2,816 bytes x 8bits per byte/1228800bps = 18.3msec

Adding the 1.7msec of base overhead gives a total base time of:

18.3msec + 1.7 = 20.0msec

Subtracting the guard band time of 25 x 150µsec or 3.75msec leaves

30msec – 20.0msec – 3.75msec = 6.25msec

Dividing this time by 26 slots yields a remote transmit slot time of

6.25msec/26 slots = 0.240msec per slot

Converting that time to bytes of data yields:

0.240msec x 1228800bps/8bits/byte = 36 bytes per slot

This corresponds to the base sending just over 750Kbps and the aggregate of the remote

throughput equaling about 250Kbps. This is clearly setup for predominantly base to

remote transmission. The balance between base and remote transmission is varied using

the Set Base Slot Size and Set Hop Duration commands. Details of these commands are

provided in the Modem Commands section of this manual.

It is often difficult to predict what throughput a remote will obtain in a point-to-

multipoint network. The worst-case scenario would be when there are 26 remotes

transmitting continuously. In this case, each remote would get 1/26th of the remote to

base aggregate throughput of about 250Kbps or about 9600bps. In practice, given the

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over-the-air data rate of the radio (1.2288Mpbs) is faster than the serial input to the radio

(921.6Kbps), it is rare that this circumstance will exist more than briefly. Also, in

applications where there are more remotes to base communication than base to remotes,

the base slot size will be reduced accordingly. These calculations are provided as a means

of only estimating the capacity of a multipoint WIT2411 network.

2.2.5. Full Duplex Communication

From an application perspective, the WIT2411 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 but rather use a Time Division Duplex (TDD) scheme.

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 remote 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 WIT2411 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 WIT2411 simply tries again on the next channel. Even if two

thirds of the band is unusable, the WIT2411 can still communicate reliably.

Data input to the WIT2411 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

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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.

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2.3. Modes of Operation

2.3.1. Control and Data Modes

The WIT2411 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 echo the value just entered and 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 de-asserted, the modem will return to

Data Mode.

The second method for entering Control Mode is to send the escape sequence :wit2411

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

only valid immediately after power up or after de-assertion 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 then de-assert

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

zc = 2 Escape sequence available at any time (default setting)

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 may be sent

at any time after a pause of at least two hop dwell times. 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. 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. Sleep Mode

To save power consumption for intermittent transmit applications, the WIT2411 supports

a Sleep Mode. Sleep Mode is entered by asserting the Sleep pin on the modem interface.

While in Sleep Mode, the modem consumes less than 50µA. This mode allows the radio

to be powered off while the remote device remains powered. After leaving Sleep Mode,

the radio must re-synchronize with the base station and re-register.

WIT2411

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 similar 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 WIT2411 supports an RF flow control mode for point-to-point operation. In this

mode, when the receive buffer of the receiving WIT2411 is close to full, the receiving

WIT2411 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 de-assert CTS stopping

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

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.

WIT2411

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 at 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 WIT2411

protocol format is described in detail below. The protocol format is selected through the

Set Protocol Mode command.

Base radios can use protocol modes to insure that a packet is transmitted to the base

without being broken up over multiple hops. Note that if the data length is set to a

number of bytes longer than the number of bytes that can be transmitted by a base on a

single hop, the packet will be discarded. For the base, this value is set by the Set Base

Slot Size command. 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.

WIT2411

Protocol Modes Definitions

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

multipoint remotes; does not support any packet types.

mode 03 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

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.

WIT2411 packet types (mode-03):

Transmit and Receive:

Base DATA 1110 1001 1100 0101 00HH HHHH 00SS SSSS LLLL LLLL LLLL LLLL <0-65536 bytes

data>

Remote DATA 1110 1001 1100 0101 0000 0000 00SS SSSS LLLL LLLL LLLL LLLL <0-65536 bytes

data>

Receive only:

CONNECT 1110 1001 1100 0101 10HH HHHH RRRR TTTT 00NN NNNN <3

byte remote ID>

DISCONNECT 1110 1001 1100 0101 11HH HHHH 0111 1111

H : handle number (0-63)

S : packet sequence number (0-63)

L : data length (0-65536)

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 65536, the maximum number of bytes

transmitted per hop is limited to the lesser of 65536 or the length specified by 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.

Handle 63 (3FH) is reserved for broadcast packets from the base to all remotes.

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

WIT2411

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

remotes.

3.1.3. Connect Packet

1110 1001 1100 0101 10HH HHHH RRRR TTTT 00NN NNNN <3-byte remote ID> (base, receive o nly)

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 1100 0101 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 1100 0101 11HH HHHH 0111 1111

H : handle number (1-62)

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.

WIT2411

4. MODEM INTERFACE

Electrical connection to the WIT2411 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 WIT2411 buffers re ceiv e data until

RTS is asserted.

(0v) 1 = Receive data (RxD) e nabled

(3.3v) 0 = Receive data (RxD) di sabled.

6 SLEEP Input Sleeps/wakes radio transceiver. In slee p mode all radio functions

are disabled consuming less than 50µA. At wake up, any user

programmed 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 (synchronized)

(3.3v) 0 = No carrier detected (not synchronized)

8 Output Clear to send. Used to co ntrol 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 - - Reserved for future use. Do not connect.

10 Input Resets the radio.

11-15 - - 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

Reset

WIT2411

4.1. Interfacing to 5 Volt Systems

The modem interface signals on the WIT2411 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 WIT2411 signal inputs. The output voltage swing of the WIT2411

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

10 k

Ω

From 5v

Output

To 3.3v Input

20 k

Ω

4.2. Evaluation Unit and 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 (SLEEP) 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 WIT2411 can be operated in a three-wire configuration using just TxD, RxD and

Ground. To operate the WIT2411 in this configuration, the Sleep and RTS signals must

be tied to ground. These signals are pulled up on the WIT2411 module and if left

disconnected will put the radio into sleep mode and RTS will be de-asserted.

The WIT2411 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 WIT2411

has a 2048-byte transmit buffer and a 1024-byte receive buffer.

WIT2411

5. MODEM COMMANDS

The WIT2411 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 arguments. 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 115,200 bps and protocol mode 0.

Command Description

sd[?|01|0f] Set Data Rate Divisor

Data Rate Divisor (hex)

115200 bps = 0f (default)

921600 bps = 01

sp[?|00|03] Set Protocol Mode (currently only mode 3 is working)

00 = point-to-point transparent mode

03 = command, data and connection notification

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.

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

network performance. Refer to the section on Protocol Modes for details on each format.

WIT2411

5.2. Network Commands

Network commands are used to set up a WIT2411 network and to set radio addressing

and configuration.

Command Description

wb[?|0|1] Set Transceiver Mode

0 = remote (default)

1 = base station

wg[?|0|1] Enable Global Network Mode (remote)

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] Set Hopping Pattern (Network Number)

0 = default

wp[?|0|1] Set Transmit Power

0 = 10mW

1 = 100mW (default)

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.

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

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 or seamless roaming is enabled. In

global and seamless 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 WIT2411 has 64 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.

WIT2411

Set Transmit Power

The WIT2411 has two preset transmit power levels, 10mW (10dBm) and 100mW

(20dBm). Control of the transmit power is provided through this command. Default is

100mW.

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 30H and improves the re-

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

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[?|0-9] Set Alternative Frequency Band

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

1 = Avoids 802.11b ba nds 1 & 2

2 = Avoids 802.11b ba nds 3 & 4

3 = Avoids 802.11b ba nds 5 & 6

4 = Avoids 802.11b bands 7 & 8

5 = Avoids 802. 11 b bands 9 & 10

6 = Avoids 802.11b bands 11 & 12

7 = Reserved

8 = Israel (~2418 – 2457MHz)

9 = Mexico/Canada (~2450 – 2483.5MHz)

xh[?|00-ff] (base only)

Set high byte of Hop Duration

02H = default

ph[?|00-ff] (base only)

Set low byte of Hop Duration

40H = default

pr[?|00-ff]

Set Packet Attempts Limit

10H = default

FFH = Infinite retry (RF flow control point-to-point only)

xw[?|00-34] (base only) Set high byte of Base Slot Size

01H = default

pw[?|00-34] (base only) Set low byte of Base Slot Size

60H = default

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.

WIT2411

Set Alternative Frequency Band

When set to a value between 1 and 6, will cause the WIT2411 to hop around the various

802.11b channels. When used in this mode, the WIT2411 will not interfere with co-

located 802.11b systems. This mode of operation is allowed by the FCC in the United

States and the ETS in Europe. For Mexico and Canadian operation, set this parameter to

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 52.1µs

increments. The default value of 240H corresponds to a duration of 30ms. 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 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 Base Slot Size (base station only)

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

slot in 52.1µs increments, corresponding to 8 bytes per unit. Default value is 160H which

corresponds to 2,816 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.

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 either successful or packet attempt limit attempts 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.

WIT2411

5.4. Status Commands

These commands deal with general interface aspects of the operation of the WIT2411.

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

2 = unlimited times (default)

zh? Read factory serial number high byte.

zm? Read factory serial number middle byte.

zl? Read factory serial number low byte.

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 ":WIT2411". When this mode is set

to 1, the escape sequence only works immediately after reset. When set to 2, the escape

sequence may be used at any time in the data stream when preceded by a pause of two

hop dwell times (this is the default). For backwards compatibility with the WIT2400, the

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

sequence must be interp reted 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.

WIT2411

5.5. Memory Commands

The WIT2411 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 WIT2411 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.

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 th e

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

WIT2411

5.6. Modem Command Summary

Serial Commands

sd[?|1|f] Set Data Rate Divisor

sp[?|0|3] Set Protocol Mode (only 0 and 3)

Network Commands

wb[?|0|1] Set Transceiver Mode

wl[?|0..ff] Set Lockout Key

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

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

wp[?|0|1] Set Transmit Power

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

Protocol Commands

pe[?|0..9] Set Alternative Frequency Band (base only)

xh,ph[?|00..ff] Set Hop Duration (base only)

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

xw,pw[?|00..ff] 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

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?.

WIT2411

6. WIT2411 DEVELOPER’S KIT

The WIT2411 Developer’s Kit contains two self-contained wireless modems (HN-511s)

built around the WIT2411M OEM module. In addition, two WIT2411M OEM modules

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

quickly using standard RS-232 or USB 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 level signals of the serial interface

and the USB interface, the self-contained modems operate exactly as the OEM modules.

The HN-511 will communicate over the USB port if that port is connected to an active

USB device. Otherwise, it will communicate of the RS-232 serial port.

Connection is made to the USB port using the standard USB cable provided. The USB

port is provided to simplify communicating to the WIT2411 module in the HN-511 at the

921,600 bps data rate. While most PCs can support that data rate through a USB port,

they are unable to do so through a standard RS-232 port.

When the HN-511 is powered up and connected to a USB port on the computer, you will

be notified that a new device has been found and will be prompted for the location where

the driver is to be found. Click on the Have Disk button and insert the CD included in the

developer’s kit. Select the drive letter of the CD drive and click continue. The USB

drivers will be installed automatically.

Connection is made to the RS-232 port of HN-511s through a standard DB-9 connector.

The HN-511s 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 7.3. 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 WIT2411 does not support software flow control.

When the developer’s kit is shipped from the factory, one HN-511 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

115,200 bps. The default settings allow 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

WIT2411

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.

WIT2411

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.

WIT2411

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.

WIT2411

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.

WIT2411

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.

WIT2411

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.

WIT2411

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.

WIT2411

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.

WIT2411

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:

WIT2411

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.

WIT2411

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.

WIT2411

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.

WIT2411

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 WIT2411 defaults to 9600 bps asynchronous.

Evaluation units do not have external access to the CFG_SEL signal; you must use the

:WIT2411 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.

WIT2411

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

known for the module to receive this command.

WIT2411

9. APPENDICES

9.1. Technical Specifications

9.1.1. Ordering Information

WIT2411D OEM Module

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, 921.6Kbps I/O)

Mode Remote Base Station

Sleep 50µA N/A

Standby 100mA N/A

Typical Average 170mA 200mA

Peak (Tx) 245mA 245mA

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 +18 dBm (+20 dBm effective radiated)

Line-of-site Range approx. 6/10 of a mile w/2dB dipole

Frequency Range 2401 – 2495MHz

Number of Channels 43, 27 or 15 depending on hop set

Receiver Sensitivity -89dBm

Channel Data Rate 1.2288Mbps

9.1.4. Mechanical Specifications

Weight 48g

Dimensions (including shield) 88.9 x 70.0 x 10.5mm

(refer to section 7.6 for mechanical drawing)

RF Connector:

WIT Huber/Suhner: 85 MMCX 50-0-1

Mating Huber/Suhner: 11 MMCX-50-2-3

(straight)

Huber/Suhner: 16 MMCX-50-2-2 (rt. angle)

Data/Power Connector:

WIT Samtec: DIS5-108-51-L-D

Mating Samtec: CLP-108-02-G-D

(PCB mount)

Samtec: FFSD-08 (IDC cable)

WIT2411

9.2. Serial Connector Pinout

Signal

WIT2411D

OEM Pinout

HN-511

DB9

Pinout

GND 1 5

TXD 2 3

RXD 3 2

CFG 4 -

RTS 5 7

SLEEP 6 4

DCD 7 1

CTS 8 8

The HN-511 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-511 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-511 can operate with just these three wires

connected. However, as the WIT2411 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-511 to the DTR and RTS inputs to activate the DTE device whenever the

WIT2411 asserts carrier.

When connecting to the WIT2411D, make sure that all of the inputs (TXD, CFG, RTS

and SLEEP) are terminated for proper operation.

9.3. Approved Antennas

The WIT2411D 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

15dB Yagi Directional 15dB YAGI2415 N

14dB Corner Refle ctor 14dB CORNER2414 N

12dB Cirronet Patch 12dB PA2412 RF cable w/MMCX

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

WIT2411

9.4. Technical Support

For technical support call Cirronet™ at (678) 684-2000 between the hours of 8:30AM

and 5:30PM Eastern Time.

WIT2411

9.5. Reference Design

TXD

RTS_3.3V

If using a 5.0V converter use the

fo ll owi ng ci rcu it fo r T XD ,DT R,R TS

DTR

DCD_3.3VDCD

VCC 3.3V

MAX3238

15 2

C1+

C1-

C2+

C2-

R1OUTB

T1OUT

T2OUT

T3OUT

T4OUT

T5OUT

R1OUT

R2OUT

R3OUT

R2IN

R3IN

R1IN

VCC

V+

V-

FORCEON

FORCEOFF

INVALID GND

T4IN

T5IN

T2IN

T3IN

T1IN

DTR_SLEEP_3.3V

RS232 Interface

MBR0520L

CTS_3.3V

1 uF

TXD_3.3V

RXD

0.1uF

RXD_3.3V

10k

1 2

0.22uF

1 uF

WIT2410 Interface

6.8k

RTS

VC C 3.3V

Optional pullups to keep

RT S and DT R ass ert ed

when left unconnected

TXD_3.3V

TXD_5V

CTS

1 uF

20k

1 2

WIT2411

9.6. Mechanical Drawing – WIT2411D

WIT2411

10. Warranty

Seller warrants solely to Buyer that the goods delivered hereunder shall be free from

defects in materials and workmanship, when given norma l, 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.