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

Murata Electronics North America WIRELESS LAN users manual

users manual

WIT5811 5.8GHz Spread Spectrum Wireless Industrial Transceiver Integration Guide 5375 Oakbrook Parkway Norcross, Georgia 30093 www.cirronet.com +1 (678) 684-2000
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. 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. 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
© 2003 Cirronet Incorporated 1 M-5811-0008 Rev - 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. - Multipath fading impervious frequency hopping technology with 75 frequency channels (5729 - 5821MHz). - Supports point-to-point or multipoint applications. - Meets FCC rules 15.247 license-free operation. - Superior range to 802.11 wireless LAN devices. - Transparent ARQ protocol w/12KB buffer ensures data integrity. - Digital addressing supports up to 64 networks, with 62 remotes per network. - Low power 3.3v CMOS signals - 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. - Nonvolatile memory stores configuration when powered off. - Smart power management features for low current consumption. - Dynamic TDMA slot assignment that maximizes throughput. 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 2 M-5811-0008 Rev - 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 3 M-5811-0008 Rev - 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 4 M-5811-0008 Rev - 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 5 M-5811-0008 Rev - 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 6 M-5811-0008 Rev - 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 7 M-5811-0008 Rev - 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 8 M-5811-0008 Rev - 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 9 M-5811-0008 Rev - 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 10 M-5811-0008 Rev - 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.
© 2003 Cirronet Incorporated 11 M-5811-0008 Rev - 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 Escape sequence disabled zc = 1 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
© 2003 Cirronet Incorporated 12 M-5811-0008 Rev - 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.
© 2003 Cirronet Incorporated 13 M-5811-0008 Rev - 3. PROTOCOL MODES In point-to-point applications, it is generally desired that the radios operate in a transparent mode. That is, raw unformatted data is sent from the host to the radio and is received as raw data at the receiving end. The addressing and error detection and correction are still performed by the radios, but it is transparent to the user application. To set up a point-to-point network, one radio has to be set up as a base station. When the radios are powered on, the base station will send out the synchronization signal at the beginning of each hop. The remote will synchronize with the base and automatically request registration. Once the remote is registered, the radios can transmit data. Protocol mode operation is available in point-to-point mode if desired. If the base station is to be responsible for directing data to a specific remote in point-to-multipoint mode, the data sent to the base station by the user application must adhere to a packet format. This allows transmissions from the base station to be directed to a specific remote. Data received by a base station from a remote is similarly formatted to identify to the user application the remote that sent the transmission. The remotes may still use transparent mode without formatting to send data to the base, if desired. The 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.
© 2003 Cirronet Incorporated 14 M-5811-0008 Rev - 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 <0-65536 bytes data> Remote DATA 1110 1001 1100 0101 0000 0000 00SS SSSS LLLL LLLL LLLL LLLL <0-65536 bytes data> Receive only: CONNECT 1110 1001 1100 0101 10HH HHHH RRRR TTTT 00NN NNNN <3 byte remote ID> DISCONNECT 1110 1001 1100 0101 11HH HHHH 0111 1111 H : handle number (0-63) S : packet sequence number (0-63) L : data length (0-65536) N : remote's previous network number (if roamed) R : receive sequence number (from previous cell) T : transmit sequence number (from previous cell) Note that while the packet length can be set to 65536, the maximum number of bytes transmitted per hop is limited to the lesser of 65536 or the length specified by maximum data length. Packets with a data length longer than that will be discarded and not sent. See Get Maximum Data Length for more details. Handle 63 (3FH) is reserved for broadcast packets from the base to all remotes. Acknowledgment requests are not supported for broadcasts. For this reason, it is a good idea to send broadcast messages several times to increase the odds of reaching all remotes.
© 2003 Cirronet Incorporated 15 M-5811-0008 Rev - 3.1.1. Connect Packet 1110 1001 1100 0101 10HH HHHH RRRR TTTT 00NN NNNN <3-byte remote ID> (base, receive only) H : handle number (0-62) R : receive sequence number (from previous cell) T : transmit sequence number (from previous cell) N : network number of the previous base (if roamed) 1110 1001 1100 0101 10HH HHHH RRRR TTTT 00NN NNNN <3-byte base ID> (remote, receive only) H : handle number (0-62) R : receive sequence number T : transmit sequence number N : network number of base Remotes must go through an automatic registration process when roaming from one base to another, after loss of contact, or when acquiring a base signal for the first time after power up. The base then assigns the remote a handle value, may or may not assign it a dedicated time slice depending on the user settings, and notifies the user application of the new remote with a connect packet. The network number of the last base the remote was connected to is given to aid user software in resending orphan packets that may have been sent to the remote's previous cell. If the remote has been powered up for the first time and this is the first base contacted, the last base ID will be reported as 80H. 3.1.2. Disconnect Packet (base only, receive only) 1110 1001 1100 0101 11HH HHHH 0111 1111 H : handle number (1-62) When a remote goes out of range or roams to another cell, the base issues a disconnect packet to indicate that the remote is no longer available.
© 2003 Cirronet Incorporated 16 M-5811-0008 Rev - 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 Type Description 1 GND - Signal and chassis ground 2 TXD Input Transmit data. Input for serial data to be transmitted. In Control Mode also used to transmit modem commands to the modem. 3 RXD Output Receive data. Output for received serial data. In Control Mode, also carries receive modem status from the modem. 4 Input Configuration selector. Used to switch between Control and Data Modes. Normally, CFG will be set for Data Mode. An internal 10K pull-up enables Data Mode if this signal is left unconnected. Control Mode is also accessible by transmitting an escape sequence immediately after wake up or power up. (0v) 1 = Control Mode (3.3v) 0 = Data Mode 5 Input Request to send. Gates the flow of receive data from the radio to the user on or off. In normal operation this signal should be asserted. When negated, the WIT5811 buffers receive data until RTS is asserted. (0v) 1 = Receive data (RxD) enabled (3.3v) 0 = Receive data (RxD) disabled. 6 SLEEP Input 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) 1 = Sleep Radio (0v) 0 = Wake Radio 7 Output Data carrier detect. For remotes, indicates the remote has successfully acquired the hopping pattern of the base station. (0v) 1 = Carrier detected (synchronized) (3.3v) 0 = No carrier detected (not synchronized) 8 Output Clear to send. Used to control transmit flow from the user to the radio. (0v) 1 = Transmit buffer not full, continue transmitting (3.3v) 0 = Transmit buffer full, stop transmitting 9 - - Reserved for future use. Do not connect. 10 Input Resets the radio. 11-15 - - Reserved for future use. Do not connect. 16 VCC - Positive supply. Min 3.3 v, 5.0 v nominal, 10.0 v max. RTS DCD CTS CFG Reset
© 2003 Cirronet Incorporated 17 M-5811-0008 Rev - 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. 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. 10 kΩ 20 kΩ From 5v Output To 3.3v Input
© 2003 Cirronet Incorporated 18 M-5811-0008 Rev - 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 Description sd[?|01|0f] Set Data Rate Divisor Data Rate Divisor (hex) 115200 bps = 0f (default) 921600 bps = 01 sp[?|00|03] Set Protocol Mode (currently only mode 3 is working) 00 = point-to-point transparent mode 03 = command, data and connection notification Set Data Rate Divisor Sets the serial bit rate between the modem and the host. This command takes effect immediately and will require adjusting the host serial rate to agree. Set Protocol Mode Enables the base station to operate in a multipoint network. Depending on the user application, more or less acknowledgment may be desired by the application. Remotes can operate in transparent mode even though the base station is operating in one of the nontransparent modes. When using a protocol mode, make sure to count in packet overhead when calculating network performance. Refer to the section on Protocol Modes for details on each format.
© 2003 Cirronet Incorporated 19 M-5811-0008 Rev - 5.2. Network Commands Network commands are used to set up a WIT5811 network and to set radio addressing and configuration. Command Description wb[?|0|1] Set Transceiver Mode 0 = remote (default) 1 = base station wg[?|0|1] Enable Global Network Mode (remote) 0 = Link only to hop pattern specified by wn parameter (default) 1 = Link to any hop pattern, regardless of wn parameter wl[?|0-ff] Set lockout key allowing network segregation beyond network number 0 = default wn[?|0-3f] Set Hopping Pattern (Network Number) 0 = default wp[?|0|1] Set Transmit Power 0 = 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.
© 2003 Cirronet Incorporated 20 M-5811-0008 Rev - 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 Description xh[?|00-ff] (base only) Set high byte of Hop Duration 02H = default ph[?|00-ff] (base only) Set low byte of Hop Duration 40H = default pr[?|00-ff] Set Packet Attempts Limit 10H = default FFH = Infinite retry (RF flow control point-to-point only) xw[?|00-34] (base only) Set high byte of Base Slot Size 01H = default pw[?|00-34] (base only) Set low byte of Base Slot Size 60H = default px[?|0|1] Set ARQ mode. 0 = ARQ enabled (default) 1 = ARQ disabled (redundant transmission) Note: Incorrect setting of these parameters may result in reduced throughput or loss of data packets. 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
© 2003 Cirronet Incorporated 21 M-5811-0008 Rev - times every transmission will be sent, regardless of success or failure of a given attempt. When this parameter is set to FFH, RF flow control mode is entered for transmissions from the radio (See Section 2.3.4). This mode can be entered for one or both radios in a point-to-point system. When used in a point-to-point system the wu parameter should be set to 1. Using this mode in a point-to-multipoint system will stop transmissions to all radios when any one radio has a full buffer or if the base radio attempts to send data to a remote that has recently (<2.5 seconds) left the range of the base. Set Base Slot Size (base station only) Sets the amount of time allocated for transmission on each hop for the base station time slot in 52.1µs increments, corresponding to 8 bytes per unit. Default value is 160H which corresponds to 2,816 bytes. If using a protocol mode, attempting to send a packet with a length longer than this setting will cause the packet to be discarded. Set ARQ Mode Sets ARQ mode when set to 0 which is the default. In this mode the radio will resend an unsuccessful transmission until either successful or packet attempt limit attempts have been made. When set to 1 selects redundant transmit mode that will send every transmission packet attempt limit times regardless of success or failure of any given attempt. When redundant transmit mode is used, receiving radios will discard all subsequent retransmissions once the transmission has been successfully received. Thus the receiving host will receive just one copy of the transmission.
© 2003 Cirronet Incorporated 22 M-5811-0008 Rev - 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.
© 2003 Cirronet Incorporated 23 M-5811-0008 Rev - 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.
© 2003 Cirronet Incorporated 24 M-5811-0008 Rev - 5.6. Modem Command Summary Serial Commands sd[?|1|f] Set Data Rate Divisor sp[?|0|3] Set Protocol Mode (only 0 and 3) Network Commands wb[?|0|1] Set Transceiver Mode wl[?|0..ff] Set Lockout Key wn[?|00..3f] Set Hopping Pattern wg[?|0|1] Enable Global Network Modes wp[?|0|1] Set Transmit Power wu[?|0|1] Set Point-to-Point Direct Mode Protocol Commands xh,ph[?|00..ff] Set Hop Duration (base only) pr[?|00..ff] Set Packet Attempts Limit xw,pw[?|00..ff] Set Base Slot Size (base only) px[?|0|1] Set ARQ Mode Status Commands zb[?|0|1] Banner Display Disable zc[?|0|1] Set Escape Sequence Mode zh? Read Factory Serial Number High Byte zm? Read Factory Serial Number Middle Byte zl? Read Factory Serial Number Low Byte z> Exit Modem Control Mode Memory Commands m0 Recall Factory Defaults m< Recall Memory m> Store Memory m! Display Changed Parameters Note: Brackets ([,]) as used here denote a set of 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?.
© 2003 Cirronet Incorporated 25 M-5811-0008 Rev - 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 26 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. F1 Toggles state of DTR (Sleep). State is shown in status line. F2 Toggles state of RTS. State is shown in status line. F3 Transmits “:wit2400”. Used to enter control mode. F5 Toggles local echo. If you are transmitting characters through one modem to another 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. 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 27 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 28 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 29 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: 6.0v to 12.0v Logic Signals 3.3v Operating Temperature Range: -40°C to +70°C Current Consumption (Max transmit power, 921.6Kbps I/O) Mode Remote Base Station Standby 450mA N/A Typical Average 500mA 550mA Peak (Tx) 830mA 830mA 7.1.3. RF Specifications FCC Certification Part 15.247, no license required Rated RF Power +24 dBm Line-of-site Range approx. 6/10 of a mile w/2dB dipole Frequency Range 5729 - 5821MHz Number of Channels 75 Receiver Sensitivity -89dBm Channel Data Rate 1.2288Mbps 7.1.4. Mechanical Specifications Weight 65g Dimensions (including shield) 120 x 95 x 16 mm (refer to section 7.6 for mechanical drawing) RF Connector: WIT Huber/Suhner: 85 MMCX 50-0-1 Mating Huber/Suhner: 11 MMCX-50-2-3 (straight) Huber/Suhner: 16 MMCX-50-2-2 (rt. angle) Data/Power Connector: WIT Samtec: DIS5-108-51-L-D Mating Samtec: CLP-108-02-G-D (PCB mount) Samtec: FFSD-08 (IDC cable)
© 2003 Cirronet Incorporated 30 M-5811-0008 Rev - 7.2. Serial Connector Pinout Signal WIT5811D OEM Pinout HN-581 DB9 Pinout GND 1 5 TXD 2 3 RXD 3 2 CFG 4 - RTS 5 7 SLEEP 6 4 DCD 7 1 CTS 8 8 The HN-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 Gain Part Number Coupling 14dB Corner Reflector 14dB CORNER5814 N 13dB Cirronet Patch 13dB PA5813 RF cable w/MMCX 9dB Omnidirectional 9dB OMNI589 N Dipole 2dB OMNI582 Reverse TNC
© 2003 Cirronet Incorporated 31 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 32 M-5811-0008 Rev - 7.5. Reference Design TXDRTS_3. 3VIf using a 5.0V converter use thefollowing circuit for TXD,DTR,RTSDTRDCD_3.3 VDCDV CC 3. 3VU5MA X3 23828251316567101221201891182627413141521917232224C1+C1-C2+C2-R1OUTBT1OUTT2OUTT3OUTT4OUTT5OUTR1OUTR2OUTR3OUTR2INR3INR1INVCCV+V-FORCEONFORCEOFFINVA LIDGNDT4INT5INT2INT3INT1INDTR_ S L EEP_ 3 . 3 VRS232 InterfaceD1MBR0520L12CTS_3. 3V+C31 uFTXD_3.3VRXDC50.1uF12RXD_3.3 VR110k1 2C10.22uF12+C41 uFWIT2410 InterfaceR16.8k12R26.8k12RTSVCC 3.3VOptional pullups to keepRTS and DTR assertedwhen left unconnectedTXD_3. 3VTXD_5VCTS+C21 uFR220k1 2WIT5811 Interface
© 2002 Cirronet Incorporated 33 M-5811-0008 Rev A 7.6.1 Mechanical Drawing – WIT5811D
© 2002 Cirronet Incorporated 347.7 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.

Navigation menu