© Radiometrix Ltd

		SPM2-433
The SpacePort Modem (SPM) is a low cost highly integrated intelligent radio packet modem that enables a radio network/link to be simply implemented between a number of digital devices. The SPM uses addressable data packets with error checking, packet acknowledgements and retransmissions to achieve a reliable invisible wireless data link. Built for ease of use and rapid installation, the serial interface ensures direct connection to microprocessors or to RS232 port via RS232 driver while remote configuration enables post installation setup of the modem.
Features Addressable point-to-point mode Point-to-Multipoint and broadcast modes Inverted RS232 interface at TTL level DTE speed 600-115200bps Air data speed 1200-14400bps Single 5V or 3.3V supply Flow control - Hardware, none Up to 200m outdoor & 50m in-door range Built-in command line configuration Built-in RF link diagnostics Remote over-air unit configuration Low operating current, Auto standby mode Conforms to ETSI EN 300 220-3 and EN 301 489-3 Dimensions - 23mm X 39mm X 6.5mm
Evaluation Platform: SPM2/RPM Evaluation Kit
Applications PDAs, organisers & laptops Telemetry and telecontrol Handheld / portable terminals EPOS equipment, barcode scanners, belt clip printers, stock control, job allocation Remote data acquisition system, data logging Audience response systems In-building environmental monitoring and control system High-end security and fire alarm signalling Restaurant ordering systems Fleet management, vehicle data acquisition
INTRODUCTION The SPM2 is a self-contained radio modem module that requires only a simple antenna, 5V supply and a serial I/O port on a host microcontroller or PC. The module provides all the RF circuits and processor intensive low level packet formatting and packet recovery functions required to inter-connect any number of microcontrollers in a radio network. A continuous stream of serial data downloaded by a Host microcontroller into the SPM serial receive buffer is transmitted by the SPM's transceiver and will "appear" in the serial buffer of the addressed SPM within radio range. Figure 1: SPM + Host µ-controller Figure 2: Physical dimensions and pinouts   TECHNICAL SPECIFICATIONS General   Operating Voltage 5V (standard)   3.3V (3V version) Operating Current             Transmitting/Receiving Average 40mA (Data streaming)           Standby/Power-down 15mA/400mA Operating frequency Single channel 433.920 MHz To be released in 869.85MHz and 914.5MHz Operating Temperature -10ºC to +55ºC Configuring options Built-in command line configurator     Interface   Serial Interface Inverted RS232 at TTL level Serial Protocol 8 data/1 stop/no parity Serial Signals RXD, TXD, CTS, WAKE Powerdown Control Via WAKE signal Serial Handshaking Selectable as CTS signal or none DTE Interface Speed 600/1200/2400/4800/9600/14400 19200/38400/57600/115200 Air Interface Speed 1200/2400/14400 bps Overall throughput                      Acknowledged 18kbps (max) for standard and 28kbps for fast variant                    Unacknowledged 30kbps (max) for standard and 55kbps for fast variant Receiver   Sensitivity -95 dBm for 1ppm BER and -90dBm for fast variant LO leakage (conducted) -70dBm Transmitter   Output Power 10mW ERP Spurious Emissions -46dB     Approvals Complies with ETSI EN 300-220-3 (radio) and ETSI EN 301 489-3 (EMC)
1. FUNCTIONAL DESCRIPTION
The SPM is a connection oriented modem module for sending and receiving serial data via an RF communications link. The SPM handles all necessary protocol related functions of validation and retries to ensure error free and uninterrupted data is sent over the communications link. All data transfers between a pair of SPMS are fully acknowledged, thus preventing the loss of data. Bit coding and checksums are used on the data packets to ensure the validity of the received data at the remote end.
1.1 OPERATING STATES The SPM has three normal operating states: · SHUTDOWN · STANDBY · CONNECTED SHUTDOWN The SHUTDOWN state is entered by asserting the WAKE/DTR input pin high (Vcc). It effectively forces the SPM into a suspended state. No communications can be made with the SPM in this state. STANDBY Immediately after power up and during normal operation, the SPM will automatically enter standby mode where it is waiting for a connection request from a remote SPM module. While in this mode a remote connection request can be received which will place the SPM into a connected state allowing it to then start receiving data from the remote unit. The connected host device can also send data to the SPM via the serial interface which will force the module to send a connection request to the remote SPM module, thus effectively setting up a logical connection between two units and allowing data to be transferred. CONNECTED On receipt of a connection request from a remote unit, the SPM immediately enters a connected state. This effectively allows the SPM modems to start sending and receiving data. In-coming data is sent to the host via the serial port in the same form as it was given to the remote SPM module.
2. The Host Interface
2.1 SIGNALS The connection to the SPM is a full duplex serial interface supporting baud rates from 600bps to 115200bps. Additional control signals are provided to assist in flow control, configuration and power saving in the SPM. Figure 3 shows an overview of the interface signals to the SPM. Pin name Pin Pin function Input /Output Description RF GND 1, 3 RF signal ground - BNC casing/coax braid connection RF 2 RF signal In/Out Antenna pin/coax core connection RF SELECT 4 Receiver Select In/Out Manual RF Receiver Enable or RF Receiver Active Indicator TX SELECT 5 Transmitter Select In/Out Manual RF Transmitter Enable or RF Transmitter Active Indicator TXD/AF 7 Transmitted Data or demodulated signal In/Out Transmitted Packetised Data to BiM2 Analogue Demodulated signal from BiM2 D3 8 SP2 Data line NC Internal data line between RPM and FRPC D2 9 SP2 Data line NC Internal data line between RPM and FRPC SIGNAL 10 Preamble Detect Out Valid preamble indicator RST 11 FRPC reset NC Resets FRPC which also isolates BiM2 RXA 12 Receive Acknowledge NC Host to FRPC download request acknowledge RXR 13 Receive Request Out Valid Data packet indicator RESET 14 Reset In Hardware reset of the SPM SETUP 15 Enter Setup In Enter SPM configurator after a reset WAKE/DTR 16 Wake or Shutdown In Wakes SPM when low, shuts down when high TXD 17 Serial transmitted data In Host (DTE) to SPM serial data RXD 18 Serial Received data Out SPM to host (DTE) serial data CTS 19 Flow control Out SPM to Host (DTE) flow control DEFAULT 20 Force 9600bps In Force the SPM serial interface to 9600bps Vcc 21 Vcc Supply In +5VDC GND 6, 22 Ground - Ground internally connected to RF GND     Notes: 1. RXD/TXD lines true data   2. The 4 input control lines are active low   3. Logic levels are 5V CMOS. See electrical specifications   4. Input control pins must be terminated, as pull-ups are not provided   5. Indicator outputs are active low which can be connected to LEDs
2.2 SpacePort Modem Reset RESET The Reset signal may either be driven by the host (recommended) or pulled up to Vcc via a suitable resistor (10kW). A reset aborts any transfers in progress and restarts the SPM. HOST DRIVEN RESET Minimum low time: 1.0 ms, after reset is released (returned high). The host should allow a delay 1ms after reset for the SPM to initialise itself.
figure 3: Host to SPM connection
2.3 HOST TO SPACEPORT DATA TRANSFER Data is transferred between the SPM and the HOST using an asynchronous serial protocol. The default protocol settings are 8 data bits, no parity and 1 stop bit (8n1). The baud rate setting for the serial interface is user settable from 600bps to 115200bps. TXD Data from the connected host is received by the SPM using TXD signal. CTS A single handshake line, CTS, controls the flow of data into the SPM. The serial receive buffer of the SPM is 96 bytes deep. The CTS will be asserted by the SPM when the receive buffer hits approximately 66% full. It is advisable to limit the number of characters sent to the SPM after the CST control line is asserted. This will help to reduce the possibility of lost data due to internal buffer overruns in the SPM. The SPM will clear the CTS when the internal serial receive buffer falls below 33% full. RXD Upon the SPM receiving data from a remote unit, the received data is sent to the connected host device using the RXD signal. 2.4 ENTERING SPACEPORT MODEM CONFIGURATOR Configuring the SPM is accomplished by using a built-in command line configurator. The configurator is entered by asserting the SETUP input of the SPM while resetting the SPM. SETUP Holding SETUP low during a reset cycle will force the modem into the configurator. The state of this input is checked while the SPM starts up from either power on or reset. HOST DRIVEN SETUP The Setup pin may either be driven by the host (recommended) to enable host controlled configuration of the SPM or pulled up to VCC via a suitable resistor (10kW). 2.5 FORCING DEFAULT SERIAL BAUD RATE Asserting this pin low forces the SPM to startup with a default baud rate of 9600bps, 8 data, one stop and not parity. DEFAULT During a RESET the HOST must hold DEFAULT low to force the SPM serial interface to default to 9600bps. This is ideal if the serial baud rate has been forgotten or incorrectly set. HOST DRIVEN DEFAULT The DEFAULT pin may either be driven by the host (recommended) or pulled up to VCC via a suitable resistor (10kW). 2.6 FORCING SPACEPORT MODEM IN TO SLEEP MODE Asserting the WAKE input high forces the modem into a low power sleep mode. This effectively shuts down the SPM and prevents it from sending or receiving any data. It is a method for conserving power when the modem is not required. WAKE/DTR During normal operation WAKE pin can be pulled low to force the SPM to shutdown into low power sleep mode. HOST DRIVEN WAKE The WAKE pin may either be driven by the host (recommended) or pulled up to 0V via a suitable resistor (10kW).
3.0 SPACEPORT CONFIGURATION 3.1 ENTERING THE CONFIGURATOR The SPM is configured by entering the built-in software configurator. Current argument can be displayed by entering parameter / command without argument
3.2 USER CONFIGURABLE PARAMETERS
CONFIG Display a list of the current SPM configuration. This wil also set FLOW control to none to enable simple 3 wire communication Valid range None DEFAULT Set all SPM configuration settings to their factory default values. Valid range None RESET Exit the modem and force a software reset. Any changed parameters will take effect after the modem has restarted. When exiting the configurator, the HOST device must ensure the SETUP pin is high otherwise the configurator will be re-entered after the reset. Valid range None UNIT Sets the unit number. Two SPM modules can communicate with each other provided they have matching Unit numbers and Site codes. default 0 Valid range 0 to 15 SITE Sets the Site address. The site number is used to distinguish between groups of operating modems. The site code is an address extension to the unit number. default 0 valid range 0 to 7 ADDR Updates the unit number value. This command is used for changing the unit number without updating the stored value. This enables the SPM to support point-to-multipoint communications.Upon using this command the configurator is exited and the modem operation is resumed. The modem is not reset when the configurator is exited. Valid range 0 to15 BAUD Sets the host interface baud rate. The changed baud rate will take effect after resetting the SPM. default 9600 valid range 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200 THRUPUT Sets the on-air data throughput. Three possible settings are provided. Max: sets the maximum data throughput of the SPM. Slots: effectively reduces the on-air throughput. This opens up 'time slots' allowing other SPM pairs, operating within close proximity, equal opportunity to transmit data. FCC: sets the on-air throughput to a rate which is compatible with FCC regulations (max 10% air time) for use in the US. default max valid range max, slots, fcc FLOW Sets the serial flow control between the host and SpacePort. Using no flow control enables the SPM to be used with a 3 wire serial link (TXD, RXD, GND). Care must be taken in order to prevent overflowing the 96 byte serial receive buffer in the SPM. Using hardware flow control enables the SPM to control the flow of serial data being received. default hw valid range hw, none SERDLY Sets the serial data receive to packet transmit delay. When the SPM receives the first byte of data from the host, it starts a timer running. Either a full buffer of data to send or a timeout of this timer will allow the packet to be transmitted. Fine tuning this delay for the baud rate the SPM is operating at can significantly increase throughput while reducing unnecessary transmissions. default 2 (x10ms) valid range 2 to 255 (x10ms) SHDN Sets the action of the WAKE input. Setting SHDN to ON will cause the SPM to monitor the WAKE input. When WAKE is taken high the SPM will be forced into low power sleep mode, thus reducing current consumption. Subsequently lowering the WAKE input will bring the SPM out of low power sleep mode. default on valid range on, off RETRY Sets the number of data retry attempts. RF interference can cause a transmitted data packet to be lost or corrupt on reception. If this happens the SPM will retransmit any unacknowledged transfer. The transmission will be retried the specified number of times before the link to the remote unit is considered 'lost' and the data purged. default 5 valid range 1 to 63 STRTMSG Enables the startup message. The startup message is enabled by default, thus giving an immediate indication of the operation of the SPM. The message can be disabled prior to deployment of the SPM module. default On valid range on, off ACKMODE Enables transfer acknowledgements. This function enables packet transfer acknowledgements to be returned for every outgoing packet. Packet acknowledgements aid in the delivery of error free and consistent data transfers between a pair of modems. Disabling the acknowledgements results in higher data throughput between modems, but does not protect against lost data due to RF interference. It should be disabled while using SPM in a broadcast mode. default On valid range on, off REMOTE Enables remote configuration. Over-air remote configuration of a SPM module is possible once it has been enabled. The remote command is used to send remote configuration commands. See the following chapter for a overview of remotely configuring a SPM module. default On valid range on, off RADAR Starts the radar test. Used as a range or confidence test between SPM modules within the same site parameter Unit number between 0 and 15.
Figure 4: SPM2 configuration using HyperTerminal
Note: To configure the SPM, the HyperTerminal should be set with the following settings. Hardware flow control should be disabled. Default baud rate of the SPM is 9600bps. However if the default baud rate of the SPM is changed then the baud rate of the HyperTerminal should be matched or DEFAULT jumper should be connected to force the SPM baud rate to 9600bps.
4.0 EXTENDED SPACEPORT FEATURES 4.1 THROUGHPUT The SPM supports two rates, MAX and SLOTS, of over-air throughput. A third rate is also provided which can be used during normal operation, but is specifically supplied for compliance with FCC regulations. MAX: When set to MAXimum and streaming data at the SPM, the data is sent as quick as possible. For host baud rates of 19200 and above, data is transmitted continuously with minimal delay between sequential packets. When this occurs, there is effectively no airtime for another pair, operating in close proximity, to transmit without causing collisions. The maximum over-air throughput that can be achieved is 14400bps.
Figure 5: A SpacePort Modem pair streaming at maximum throughput
SLOTS: Setting the throughput to Slots provides a method of opening 'time slots' for other SPM pairs operating in close proximity. The effective streaming on-air throughput between a pair of SPM is effectively reduced to approximately 2400bps.
Figure 6: Two SpacePort Modem pairs operating at Slots throughput
FCC: This setting is effectively the same as Slots, however it further slows the over-air throughput to approximately 1200bps. This mode is provided to enforce the modem to comply with FCC regulations of 10% maximum airtime usage. The THRUPUT should be set to FCC for all SPM modules used in all equipment subject to FCC regulations.
4.2 REMOTE CONFIGURATION Remote configuration of a SPM module is possible using the REMOTE command from within the configurator. Initially the REMOTE command is used to enable and disable the ability to remotely configure a module, as described in section 3.2: User Configurable Command. Once remote configuration is enabled the REMOTE command is then used to issue configuration commands to a remote SPM. The format for the remote command then becomes:
REMOTE <SERIAL NUM> <COMMAND> <PARAMTER>
The <SERIAL NUMBER> of the remote SPM must be known in order for the remote configuration request to be executed on the appropriate SPM module.
The <COMMAND> to be executed can be any of the following:
Baud 600,1200,2400,4800,9600,19200,38400,57600,115200 Unit 0 to 15 Site 0 to 7 Shdn on/off Flow hw/none Serdly 2 to 255 Retry 1 to 63 Signon on/off
The <PARAMETER> is optional, and if not specified the setting for that command is returned and displayed.
4.3 POINT-TO-MULTIPOINT The SPM can be used for point-to-multipoint communications. One module must be considered to be the master, which is used to address up to 15 remote units in any one site. During normal operation, the base unit can be set to address another unit dynamically by entering the configurator and using the ADDR command to change the unit address. Upon execution of this command, provided the parameters are correct, the configurator is exited immediately. A period ('.') is sent to the connected host device to indicate that the change has been registered and the SPM is now ready for communications to the new unit address. ADDR is very similar to the Unit command, except that ADDR does not update the stored EEPROM unit value. As the EEPROM has a limited number of write cycles, using ADDR for addressing multiple units in a point to multipoint network is recommended. Also, the ADDR command will exit the configurator immediately, which is requires to resume communications very quickly.
4.4 BROADCAST MULTIDROP The SPM has a broadcast mutidrop mode which provides a mechanism for building a large networks. This mode of operation is determined by the configuration command keyword ACKMODE being set to OFF. In broadcast mutidrop mode, the SPM does not implement network layer functionality related to data packet routing, acknowledgement and retries. The connected host device should provide network layer functionality. The site code and unit address is still used by the radio modem when working in broadcast multidrop mode. For a given multipoint network all radio modems within a group must contain the same site code and unit address.
4.5 RADAR: DIAGNOSTIC TEST Built into the configurator is a diagnostic test suitable for range testing and link confidence testing. The Radar test effectively sends a small request packet to a remote unit then waits for a reply. The remote unit must not be in the configurator otherwise it will not respond. Upon receipt of a positive response from the remote unit, a success is recorded before the process is repeated. This test will continue indefinitely until it is ended by a key press.
4.6 SpacePort Modem Error Handling The SPM's radio decoder module is deliberately non bit error tolerant, i.e. no attempt is made to repair corrupt data bits. All of the redundancy in the code is directed towards error checking. For an FM radio link using short packet lengths, packets are either 100% or so grossly corrupt as to be unrecoverable. By the same reasoning, the Host is not informed or sent corrupt data since corrupt information is of little value. The SPM implements packet acknowledges, timeouts and re-transmission accomplish reliable error handling.
Appendix A
figure 7: SPM with DCE type RS232 interface Click on the image for EXPANDED VIEW
Appendix B
figure 8, 9: FRPC, RPM pin outs Click on the image for EXPANDED VIEW
Ordering Information
Part no. Max. throughput Sensitivity Supply SPM2-433-18 (standard) 18kbps -95dBm 5V SPM2-433-18-3V 18kbps -95dBm 3.3V         SPM2-433-28 28kbps -90dBm 5V
Limitation of liability The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd reserves the right to make changes or improvements in the design, specification or manufacture of its subassembly products without notice. Radiometrix Ltd does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. This data sheet neither states nor implies warranty of any kind, including fitness for any particular application. These radio devices may be subject to radio interference and may not function as intended if interference is present. We do NOT recommend their use for life critical applications. The Intrastat commodity code for all our modules is: 8542 6000. R&TTE Directive After 7 April 2001 the manufacturer can only place finished product on the market under the provisions of the R&TTE Directive. Equipment within the scope of the R&TTE Directive may demonstrate compliance to the essential requirements specified in Article 3 of the Directive, as appropriate to the particular equipment. Further details are available on The Office of Communications (Ofcom) web site: Licensing policy manual
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