Murata WIT910 Quick setup guide

©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com
WIT910 900 MHz
Spread Spectrum
Wireless Industrial
Transceiver
Integration *XLGH

Important Regulatory Information
Cirronet Product FCC ID: HSW-910M
IC 4492A-910M
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 8.5 dBi Yagi antenna with the WIT910.
FCC rules limit the use of this antenna, when connected to the WIT910 module, to 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 applications, omni-directional applications, and
applications where there are multiple co-located intentional radiators transmitting the same
information. Any other mode of operation using this antenna is forbidden.
Notice to WIT910 users/installers using the following fixed antennas:
Cushcraft 8.5 dBi Yagi
The field strength radiated by this antenna, when connected to a transmitting WIT910, 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 23 cm from the radiating
aperture of this antenna. End users of these systems must also be informed that RF exposure
limits may be exceeded if personnel come closer than 23 cm to the aperture of this antenna.
Notice to WIT910 users/installers using the following fixed antennas:
Cushcraft 6 dBi Monopole Cushcraft 3 dBi Omni Ace 2dBi dipole
The field strength radiated by any one of these antennas, when connected to a transmitting
WIT910, may not 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.
Changes or modifications not expressly approved by the party responsible may void the users ability to
operate the equipment.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com

TABLE OF CONTENTS
1. INTRODUCTION ......................................................................................................................1
1.1 Why Spread Spectrum? ........................................................................................................1
1.2 Frequency Hopping vs. Direct Sequence..............................................................................2
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....................................................................................................6
2.2.4. 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............................................................................................................10
2.3.1. Control and Data Modes ..........................................................................................10
2.3.2. Sleep Mode ..............................................................................................................10
2.3.3. Low Power Mode and Duty Cycling .......................................................................11
2.3.4. RF Flow Control Mode.............................................................................................11
3. PROTOCOL MODES ..............................................................................................................12
3.1.1. Data Packet ..............................................................................................................14
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 OEM Module Differences .................................................................17
4.3 Three Wire Operation.........................................................................................................17
4.4 Power-On Reset Requirements...........................................................................................18
4.6 Received Signal Strength Indicator ....................................................................................19
5. MODEM COMMANDS...........................................................................................................20
5.1 Serial Commands................................................................................................................20
5.2 Network Commands...........................................................................................................22
5.3 Protocol Commands............................................................................................................24
5.4 Status Commands ...............................................................................................................27
5.5 Memory Commands ...........................................................................................................28
5.6 Modem Command Summary..............................................................................................29
6. WIT910 DEVELOPER’S KIT .................................................................................................30
7. WinCOM...................................................................................................................................31
Starting the program ..................................................................................................................33
Function Keys............................................................................................................................36
WinCom Tools...........................................................................................................................37
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com

Script Commands.......................................................................................................................39
Demonstration Procedure ..........................................................................................................41
7.6 Troubleshooting..................................................................................................................42
8. APPENDICES ..........................................................................................................................44
8.1 Technical Specifications.....................................................................................................44
8.1.1. Ordering Information...............................................................................................44
8.1.2. Power Specifications................................................................................................44
8.1.3. RF Specifications.....................................................................................................44
8.1.4. Mechanical Specifications .......................................................................................44
8.2 Serial Connector Pinouts ....................................................................................................45
8.3 Approved Antennas ............................................................................................................45
8.4 Technical Support...............................................................................................................46
8.5 Reference Design................................................................................................................47
8.6 Mechanical Drawing – WIT910 .........................................................................................48
8.7 Warranty .............................................................................................................................49
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com

WIT910
1. INTRODUCTION
The WIT910 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 900MHz ISM band allows
license-free use and worldwide compliance. Standard communication rates between the
WIT910 and the host are supported between 2400bps and 115bps. Non-standard rates
are supported as well. An on-board 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 54 frequency channels
(902 to 927 MHz).
- Supports point-to-point or
multipoint applications.
- Meets FCC rules 15.247 for
license-free operation.
- 20+ mile range with omni
antenna.
- Transparent ARQ protocol
w/512byte buffer ensures data
integrity.
- Digital addressing supports up to
64 networks, with 62 remotes per
network.
- Low power 3.3v CMOS signals
- Selectable 10mW, 100mW or
500mW 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 up to 115.2 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
its range. At any given time, multipath fades will typically occupy 1% - 2% of the
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.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
1 of 49
www.murata.com

WIT910
2
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
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.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
2 of 49
www.murata.com

WIT910
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 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.
3
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
3 of 49
www.murata.com

WIT910
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 54 frequencies and the remote is
scanning 54 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. 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 the duty cycle.
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 unless
data transmit delay has been set. The data transmit delay parameter allows for the
transmission of groups of continuous data in transparent mode (protocol mode 00H). The
amount of data that the base station can transmit per hop is determined by the base slot
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
4 of 49
www.murata.com

WIT910
size parameter. The maximum amount of data sent by a base station per hop is 208 bytes.
If there is no data to be sent, the base station will not transmit 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 registered remotes. 212 bytes per hop is the
maximum data length a remote can transmit per hop, subject to limitations imposed by
the hop duration, the base slot size and the number of registered remotes. A detailed
explanation of this relationship is provided in Section 2.2.3. Minimum data length and
data transmit delay operate the same as with the base station.
Except for the registration process which occurs only when a remote logs onto the
network, the whole procedure is repeated on every frequency hop. Refer to the section
on Modem Commands for complete details on parameters affecting the transmission of
data.
2.2 Data Transmission
The WIT910 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. It should be noted that point-to-point mode is a
subset of point-to-multipoint mode and therefore there is no need to specify one mode or
the other.
2.2.1. Point-to-Point
In point-to-point mode, unless data transmit delay or minimum data length have been set,
the base station will transmit whatever data is in its buffer limited to 188 bytes or as
limited by the base slot size. If the base station has more data than can be sent on one
hop, the remaining data will be sent on subsequent hops. In addition to the data, the base
station adds some information to the transmission over the RF link. It adds the address of
the remote to which it is transmitting, even though in a point-to-point mode there is only
one remote. It also adds a sequence number to identify the transmission to the remote.
This is needed in the case of acknowledging successful transmissions and retransmitting
unsuccessful transmissions. Also added is a 24-bit CRC to allow the base to check the
received transmission for errors. When the remote receives the transmission, it will
acknowledge the transmission if it was received without errors. If no acknowledgment is
received, the base station will retransmit the same data on the next frequency hop.
In point-to-point mode, a remote will transmit whatever data is in its buffer up to the limit
of its maximum data length. If desired, minimum data length and data transmit delay can
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
5 of 49
www.murata.com

WIT910
also be set, which force the remote to wait until a certain amount of data is available or
the specified delay is exceeded before transmitting. If the remote has more data than can
be sent on one hop, it will send as much data as possible as a packet, adding its own
address, a packet sequence number and 24-bit CRC. These additional bytes are
transparent to the user application if the protocol mode is 00H (which is the default). In
the event a remote has more data to send, the data will be sent on subsequent hops. If the
transmission is received by the base station without errors, the base station will
acknowledge the transmission. If the remote does not receive an acknowledgment, it will
retransmit the data on the next frequency hop. To the user application, acknowledgments
and retransmissions all take place behind the scenes without the need for user
intervention.
The WIT910 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.
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.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
6 of 49
www.murata.com