Murata Electronics North America 5811M WIRELESS LAN User Manual users manual

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WIT5811
5.8GHz Spread Spectrum
Wireless Industrial Transceiver
Integration Guide
5375 Oakbrook Parkway
Norcross, Georgia 30093
www.cirronet.com
+1 (678) 684-2000
Note: This unit has been tested and found to
comply with the limits for a class B 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 his
own expense. Commensurate with EIRP limits
specified in FCC Rules 15.247b, this device may
not be used with antennas that exceed 36dB of
gain in point-to-point applications or 16dB of gain
in multi-point applications.
If the WIT5811 is installed within another device the outside of the device into which the
WIT5811 is installed must also display a label referring to the enclosed module. The label
required for the WIT5811 module is as follows: Transmitter Module FCCID: HSW-5811M.
About This Manual
This manual is designed to allow integration of the Cirronet WIT5811 OEM module into
complete products. Care has been taken to try and make sure all of the information in this
manual is accurate. However, specifications can change over time and Cirronet cannot guarantee
the accuracy of this information. If you have any questions on any information in this manual,
please contact Cirronet Technical Support at +1-678 684 2000.
Cirronet is a trademark of Cirronet Incorporated. All other trademarks belong to their
respective companies.
INFORMATION TO THE USER
FCC Class B:
“NOTE: This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation. This equipment
generates, uses and can radiate radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful interference to radio communications.
However, there is no guarantee that interference will not occur in a particular installation. If this
equipment does cause harmful interference to radio or television reception, which can be
determined by turning the equipment off and on, the user is encouraged to try to correct the
interference by one or more of the following measures:
•
•
•
•
Reorient or relocate the receiving antenna.
Increase the separation between the equipment and receiver.
Connect the equipment into an outlet on a circuit different from that to which the
receiver is connected.
Consult the dealer or an experienced radio/TV technician for help.”
All Equipment:
Warning: Changes or modifications to this device not expressly approved by Cirronet
Incorporated could void the user’s authority to operate the equipment.
RF Exposure (Intentional Radiators Only)
In accordance with FCC requirements of human exposure to radiofrequency fields, the radiating
element shall be installed such that a minimum separation distance of 20 cm will be maintained.
Industry Canada
All Equipment:
This Class [B] digital apparatus meets all requirements of the Canadian Interference Causing
Equipment Regulations. Operation is subject to the following two conditions: (1) this device
may not cause harmful interference, and (2) this device must accept any interference received,
including interference that may cause undesired operation.
Cet appareillage numérique de la classe [B] répond à toutes les exigences de l'interférence
canadienne causant des règlements d'équipement. L'opération est sujette aux deux conditions
suivantes: (1) ce dispositif peut ne pas causer l'interférence nocive, et (2) ce dispositif doit
accepter n'importe quelle interférence reçue, y compris l'interférence qui peut causer
l'opération peu désirée.
Notice to WIT5811 users/installers using the following fixed antennas:
Mobile Mark 14dBi Corner Reflector ,
Cirronet 14dBi patch,
The field strength radiated by any one of these antennas, when connected to a transmitting
WIT5811 module, may exceed FCC mandated RF exposure limits. FCC rules require
professional installation of these antennas in such a way that the general public will not be closer
than 20 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 20 cm
to the apertures of any of these antennas.
Notice to WIT5811 users/installers using the following mobile antennas:
Mobile Mark 9dBi omnidirectional,
Mobile Mark 2dBi dipole
The field strength radiated by any one of these antennas, when connected to a transmitting
WIT5811 module, may exceed FCC mandated RF exposure limits. FCC rules require
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.
TABLE OF CONTENTS
1. INTRODUCTION .................................................................................................................. 1
1.1. Why Spread Spectrum? .................................................................................................. 1
1.2. Frequency Hopping vs. Direct Sequence........................................................................ 3
2. RADIO OPERATION ............................................................................................................ 4
2.1. Synchronization and Registration .................................................................................. 4
2.2. Data Transmission ......................................................................................................... 5
2.2.1. Point-to-Point ........................................................................................................ 5
2.2.2. Point-to-Multipoint ................................................................................................. 6
2.2.3. Handle Assignment ............................................................................................... 7
2.5.8. TDMA Operation ................................................................................................... 7
2.2.5. Full Duplex Communication .................................................................................. 9
2.2.6. Error-free Packet Transmission Using ARQ.......................................................... 9
2.3. Modes of Operation ..................................................................................................... 11
2.3.1. Control and Data Modes ..................................................................................... 11
2.3.2. Sleep Mode......................................................................................................... 11
2.3.4. RF Flow Control Mode ........................................................................................ 11
3. PROTOCOL MODES ......................................................................................................... 13
3.1.3. Connect Packet................................................................................................... 15
3.1.4. Disconnect Packet (base only, receive only)...................................................... 15
4. MODEM INTERFACE......................................................................................................... 16
4.1. Interfacing to 5 Volt Systems ....................................................................................... 17
4.2. Evaluation Unit and Module Differences ...................................................................... 17
4.3. Three-Wire Operation .................................................................................................. 17
5. MODEM COMMANDS........................................................................................................ 18
5.1. Serial Commands ........................................................................................................ 18
5.2. Network Commands..................................................................................................... 19
5.3. Protocol Commands .................................................................................................... 20
5.4. Status Commands ....................................................................................................... 22
5.5. Memory Commands..................................................................................................... 23
5.6. Modem Command Summary ....................................................................................... 24
6. WIT5811 DEVELOPER’S KIT ............................................................................................ 25
6.1. WinCOM24 .................................................................................................................. 26
6.2. Demonstration Procedure ............................................................................................ 26
6.3. Troubleshooting ........................................................................................................... 27
7. APPENDICES .................................................................................................................... 29
7.1. Technical Specifications............................................................................................... 29
7.1.1 Ordering Information .......................................................................................... 29
7.1.2. Power Specifications........................................................................................... 29
7.1.3. RF Specifications ................................................................................................ 29
7.1.4. Mechanical Specifications................................................................................... 29
7.2. Serial Connector Pinout ............................................................................................... 30
7.3. Approved Antennas ..................................................................................................... 30
7.4. Technical Support ........................................................................................................ 31
7.5. Reference Design ........................................................................................................ 32
7.6.1 Mechanical Drawing – WIT5811D.............................................................................. 33
7.7 Warranty ....................................................................................................................... 34
1. INTRODUCTION
The WIT5811 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 5.8GHz 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.
Simple serial interface handles both
data and control at 115,200 or
921600 bps.
Fast acquisition typically locks to
hopping pattern in 2 seconds or less.
Selectable 25 mW or 250 mW
transmit power.
Built-in data scrambling reduces
possibility of eavesdropping.
Transparent ARQ protocol
w/12KB buffer ensures data
integrity.
Nonvolatile memory stores
configuration when powered off.
Smart power management features
for low current consumption.
Digital addressing supports up to
64 networks, with 62 remotes per
network.
Dynamic TDMA slot assignment
that maximizes throughput.
Low power 3.3v CMOS signals
Multipath fading impervious
frequency hopping technology
with 75 frequency channels
(5729 - 5821MHz).
Supports point-to-point or
multipoint applications.
Meets FCC rules 15.247 licensefree operation.
Superior range to 802.11 wireless
LAN devices.
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 5.8 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.
© 2003 Cirronet Incorporated
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Spread spectrum reduces the vulnerability of a radio system to interference from both
jammers and multipath fading 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
© 2003 Cirronet Incorporated
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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.
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 wide, they tend to
offer few non-overlapping channels, whereas multiple hoppers may interleave with less
© 2003 Cirronet Incorporated
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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.
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 75 frequencies and the remote is
scanning up to 75 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 remotes 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.
© 2003 Cirronet Incorporated
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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 transmits 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 transmit data until the next
frequency.
The operation for remotes 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 WIT5811 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 buffer 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
© 2003 Cirronet Incorporated
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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 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.
The WIT5811 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 intended 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
© 2003 Cirronet Incorporated
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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 remote 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.
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 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.
2.5.8. TDMA Operation
In the WIT5811 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
© 2003 Cirronet Incorporated
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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 remote 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 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
© 2003 Cirronet Incorporated
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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 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 is 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 WIT5811 network.
2.2.5. Full Duplex Communication
From an application perspective, the WIT5811 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 5.8GHz 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 WIT5811 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
WIT5811 simply tries again on the next channel. Even if two thirds of the band are
unusable, the WIT5811 can still communicate reliably.
Data input to the WIT5811 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
© 2003 Cirronet Incorporated
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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.
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2.3. Modes of Operation
2.3.1. Control and Data Modes
The WIT5811 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 :wit5811 (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
zc = 1
Escape sequence disabled
Escape sequence available at any time (default setting)
The zc1 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 WIT5811 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.
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
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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 WIT5811 supports an RF
flow control mode for point-to-point operation. In this mode, when the receive buffer of the
receiving WIT5811 is close to full, the receiving WIT5811 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.
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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-topoint 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-tomultipoint 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 WIT5811
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
that is 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 modems 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.
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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.
WIT5811 packet types (mode-03):
Transmit and Receive:
Base
DATA
1110 1001 1100 0101 00HH HHHH 00SS SSSS LLLL LLLL LLLL LLLL
Remote DATA
1110 1001 1100 0101 0000 0000 00SS SSSS LLLL LLLL LLLL LLLL
<0-65536 bytes data>
<0-65536 bytes data>
Receive only:
CONNECT
remote ID>
DISCONNECT
1110 1001
1100 0101 10HH HHHH
RRRR TTTT
1110 1001
1100 0101 11HH HHHH
0111 1111
00NN NNNN
<3 byte
handle number (0-63)
packet sequence number (0-63)
data length (0-65536)
remote's previous network number (if roamed)
receive sequence number (from previous cell)
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 idea
to send broadcast messages several times to increase the odds of reaching all remotes.
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3.1.1. Connect Packet
1110 1001 1100 0101
10HH HHHH
1110 1001
00NN NNNN
<3-byte remote ID> (base, receive only)
handle number (0-62)
receive sequence number (from previous cell)
transmit sequence number (from previous cell)
network number of the previous base (if roamed)
1100 0101 10HH HHHH
RRRR TTTT
RRRR TTTT
00NN NNNN
<3-byte base ID> (remote, receive only)
handle number (0-62)
receive sequence number
transmit sequence number
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.
3.1.2. Disconnect Packet (base only, receive only)
1110 1001
1100 0101 11HH HHHH
0111 1111
: 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.
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4. MODEM INTERFACE
Electrical connection to the WIT5811 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
GND
Type
Description
Signal and chassis ground
TXD
Input
Transmit data. Input for serial data to be transmitted. In Control
Mode also used to transmit modem commands to the modem.
RXD
Output
Receive data. Output for received serial data. In Control Mode,
also carries receive modem status from the modem.
CFG
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)
(3.3v)
RTS
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 WIT5811 buffers receive data until
RTS is asserted.
(0v)
(3.3v)
SLEEP
Input
DCD
Output
1 = Receive data (RxD) enabled
0 = Receive data (RxD) disabled.
Sleeps/wakes radio transceiver. In sleep 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)
(0v)
1 = Control Mode
0 = Data Mode
1 = Sleep Radio
0 = Wake Radio
Data carrier detect. For remotes, indicates the remote has
successfully acquired the hopping pattern of the base station.
(0v)
(3.3v)
1 = Carrier detected (synchronized)
0 = No carrier detected (not synchronized)
CTS
Output
10
Reset
Input
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.
© 2003 Cirronet Incorporated
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
Reserved for future use. Do not connect.
Resets the radio.
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4.1. Interfacing to 5 Volt Systems
The modem interface signals on the WIT5811 are 3.3volt signals. To interface to 5volt
signals, the resistor divider network shown below must be placed between the 5 volt signal
outputs and the WIT5811 signal inputs. The output voltage swing of the WIT5811 3.3 volt
signals is sufficient to drive 5volt logic inputs.
10 kΩ
From 5v
Output
To 3.3v Input
20 kΩ
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 WIT5811 can be operated in a three-wire configuration using just TxD, RxD and
Ground. To operate the WIT5811 in this configuration, the Sleep and RTS signals must be
tied to ground. These signals are pulled up on the WIT5811 module and if left disconnected
will put the radio into sleep mode and RTS will be de-asserted.
The WIT5811 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 WIT5811 has a
8192-byte transmit buffer and a 4096-byte receive buffer.
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5. MODEM COMMANDS
The WIT5811 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 respond 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
sd[?|01|0f]
Description
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.
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5.2. Network Commands
Network commands are used to set up a WIT5811 network and to set radio addressing and
configuration.
Command
wb[?|0|1]
Description
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
Set Hopping Pattern (Network Number)
0 = default
wn[?|0-3f]
wp[?|0|1]
Set Transmit Power
0 = 25mW
1 = 250mW (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 ordinarily 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 WIT5811 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.
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Set Transmit Power
The WIT5811 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
xh[?|00-ff]
(base only)
Set high byte of Hop Duration
02H = default
(base only)
Set low byte of Hop Duration
40H = default
ph[?|00-ff]
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
(base only)
Set low byte of Base Slot Size
60H = default
pw[?|00-34]
px[?|0|1]
Description
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.
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
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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-topoint 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.
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5.4. Status Commands
These commands deal with general interface aspects of the operation of the WIT5811.
Command
Description
zb[?|0|1]
Banner Display Disable
0 = disabled
1 = enabled (default)
zc[?|0|1]
Set Escape Sequence Mode
0 = disabled
1 = unlimited times (default)
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
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 ":WIT5811". When this mode is set to 1, 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 interpreted as data by the radio until the last character is received, and as such
generally will 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.
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5.5. Memory Commands
The WIT5811 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
m0
Recall Factory Defaults
m<
Recall Memory
m>
Store Memory
m!
Display Modified Parameters
Recall Factory Defaults
Resets the WIT5811 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 time 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 the base and
will cause all remotes to lose link when issued to the base radio.
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5.6. Modem Command Summary
Serial Commands
sd[?|1|f]
sp[?|0|3]
Set Data Rate Divisor
Set Protocol Mode (only 0 and 3)
Network Commands
wb[?|0|1]
wl[?|0..ff]
wn[?|00..3f]
wg[?|0|1]
wp[?|0|1]
wu[?|0|1]
Set Transceiver Mode
Set Lockout Key
Set Hopping Pattern
Enable Global Network Modes
Set Transmit Power
Set Point-to-Point Direct Mode
Protocol Commands
xh,ph[?|00..ff]
pr[?|00..ff]
xw,pw[?|00..ff]
px[?|0|1]
Set Hop Duration
Set Packet Attempts Limit
Set Base Slot Size
Set ARQ Mode
(base only)
(base only)
Status Commands
zb[?|0|1]
zc[?|0|1]
zh?
zm?
zl?
z>
Banner Display Disable
Set Escape Sequence Mode
Read Factory Serial Number High Byte
Read Factory Serial Number Middle Byte
Read Factory Serial Number Low Byte
Exit Modem Control Mode
Memory Commands
m0
m<
m>
m!
Recall Factory Defaults
Recall Memory
Store Memory
Display Changed Parameters
Note: Brackets ([,]) as used here denote a set of optional 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?.
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6. WIT5811 DEVELOPER’S KIT
The WIT5811 Developer’s Kit contains two self-contained wireless modems (HN-581s) built
around the WIT5811M OEM module. In addition, two WIT5811M 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-581 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 WIT5811 module in the HN-581 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-581 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-581s through a standard DB-9 connector. The
HN-581s 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 WIT5811
does not support software flow control.
When the developer’s kit is shipped from the factory, one HN-581 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 DTR de© 2003 Cirronet Incorporated
25
M-5811-0008 Rev -
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.
6.1. WinCOM
Provided with the developer’s kit is a simple communications program designed especially
for the WIT5811. The WinCOM program provides a simple command interface to the
modems along with function key control for manipulating the serial port control lines and
baud rates. This program is designed to run under Windows®.
WinCOM will automatically detect to which port and at which baud rate the HN-581 is
communicating. These settings will be displayed.
Note that the data rate applies to the serial port of the computer. This parameter has no effect
on the modem. If the modem is set for 115,200bps but WinCOM is invoked to run at
921,600bps, the computer and the modem will be unable to communicate.
Toggles state of DTR (Sleep). State is shown in status line.
Toggles state of RTS. State is shown in status line.
Transmits “:wit2400”. Used to enter control mode.
Toggles local echo. If you are transmitting characters through one modem to
another WIT5811, this allows you to see what you are typing.
F6
Transmits data string. Causes WinCOM24 to transmit the data string entered
in the data window a single time. 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 WIT5811 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.
F1
F2
F3
F5
The values of DTR (Sleep), RTS, DSR, CTS, DCD and the PC serial port rate are displayed
in the status line at the bottom of the display.
6.2. Demonstration Procedure
The procedure below provides a quick demonstration of the WIT5811.
1. Attach a transceiver to each computer, preferably between 5' and 30' apart for
convenience.
© 2003 Cirronet Incorporated
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M-5811-0008 Rev -
2. Start WinCOM running on both computers by double-clicking on the WinCOM icon. If
you prefer, almost any other serial communications program such as Procomm or
QModem set for 115,200 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 WinCOM, 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 the 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 WinCOM, 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 WinCOM by pressing the ESC key.
6.3. 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 WIT5811 defaults to 921,600 bps asynchronous.
Evaluation units do not have external access to the CFG_SEL signal; you must use the
:WIT5811 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.
© 2003 Cirronet Incorporated
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M-5811-0008 Rev -
Carrier is detected, but no data appears to be received.
Make sure that RTS is asserted to enable receive character flow. In a point-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.
This indicates that the transmitter is unable to reliably get its data across. This may 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.
© 2003 Cirronet Incorporated
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M-5811-0008 Rev -
7. APPENDICES
7.1. Technical Specifications
7.1.1 Ordering Information
WIT5811D
OEM Module
7.1.2. Power Specifications
Vcc Input Range:
Logic Signals
Operating Temperature Range:
6.0v to 12.0v
3.3v
-40°C to +70°C
Current Consumption (Max transmit power, 921.6Kbps I/O)
Mode
Standby
Typical Average
Peak (Tx)
Remote
450mA
500mA
830mA
Base Station
N/A
550mA
830mA
7.1.3. RF Specifications
FCC Certification
Rated RF Power
Line-of-site Range
Frequency Range
Number of Channels
Receiver Sensitivity
Channel Data Rate
Part 15.247, no license required
+24 dBm
approx. 6/10 of a mile w/2dB dipole
5729 - 5821MHz
75
-89dBm
1.2288Mbps
7.1.4. Mechanical Specifications
Weight
Dimensions (including shield)
65g
120 x 95 x 16 mm
(refer to section 7.6 for mechanical drawing)
RF Connector:
WIT
Mating
Data/Power Connector:
WIT
Mating
© 2003 Cirronet Incorporated
Huber/Suhner: 85 MMCX 50-0-1
Huber/Suhner: 11 MMCX-50-2-3 (straight)
Huber/Suhner: 16 MMCX-50-2-2 (rt. angle)
Samtec: DIS5-108-51-L-D
Samtec: CLP-108-02-G-D (PCB mount)
Samtec: FFSD-08 (IDC cable)
29
M-5811-0008 Rev -
7.2. Serial Connector Pinout
Signal
GND
TXD
RXD
CFG
RTS
SLEEP
DCD
CTS
HN-581
DB9
Pinout
WIT5811D
OEM Pinout
The HN-581 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-581 to a DTE device, a “null
modem” cable is required. To effect a null modem cable, cross-wire TXD and RXD and
connect ground. The HN-581 can operate with just these three wires connected. However,
as the WIT5811 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-581 to the DTR and
RTS inputs to activate the DTE device whenever the WIT5811 asserts carrier.
When connecting to the WIT5811D, make sure that all of the inputs (TXD, CFG, RTS and
SLEEP) are terminated for proper operation.
7.3. Approved Antennas
The WIT5811D 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
14dB Corner Reflector
13dB Cirronet Patch
9dB Omnidirectional
Dipole
© 2003 Cirronet Incorporated
Gain
14dB
13dB
9dB
2dB
Part Number
CORNER5814
PA5813
OMNI589
OMNI582
30
Coupling
RF cable w/MMCX
Reverse TNC
M-5811-0008 Rev -
7.4. Technical Support
For technical support call Cirronet at +1 678 684 2000 between the hours of 8:30AM and
5:30PM Eastern Time.
© 2003 Cirronet Incorporated
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M-5811-0008 Rev -
7.5. Reference Design
Optional pullups to keep
RTS and DTR asserted
when left unconnected
D1
RS232 Interface
11
TXD
12
10
RXD
DCD
CTS
16
V CC 3.3V
13
14
15
C5
0.1uF
C2+
C3
1 uF
C1V-
C2
1 uF
27
25
R2
6.8k
V+
R1
6.8k
C1
0.22uF
C1+
26
V CC
28
DTR
RTS
V CC 3.3V
U5
C4
1 uF
C2R1IN
R2IN
R3IN
T5OUT
T4OUT
T3OUT
T2OUT
T1OUT
R1OUT
R2OUT
R3OUT
T5IN
T4IN
T3IN
T2IN
T1IN
21
20
18
TXD_3.3V
DTR_SLEEP_3.3V
RTS_3.3V
17
19
22
23
24
RXD_3.3 V
DCD_3.3 V
CTS_3.3V
WIT5811 Interface
Interface
WIT2410
R1OUTB
FORCEON
FORCEOFF
INVA LID
MA X3 238
GND
If using a 5.0V converter use the
following circuit for TXD,DTR,RTS
TXD_5V
R1
10k
TXD_3.3V
MBR0520L
R2
20k
© 2003 Cirronet Incorporated
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M-5811-0008 Rev -
7.6.1 Mechanical Drawing – WIT5811D
© 2002 Cirronet Incorporated
33
M-5811-0008 Rev A
7.7 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.
© 2002 Cirronet Incorporated
34

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