RS232 LOW COST RF MODEM FM-232C-433 FEATURES • • • • • • • • • • • • • Industry Standard RS-232. Automatic Data Packetising, Error Checking (Transparent link). Available at 433MHz (10mW ERP) Range upto 120 Metres Network Configurable, User Selectable as Master or Slave 56 Byte Data Buffer Broadcast Facility User Selectable Baud Rate 9600, 4800, 2400, 1200, Half Duplex Optional H/W or S/W Flow Control LED Indication of Data Tx, Rx, CD. 9-30Vdc Power Supply Requires no radio Licence To Operate Miniature enclosure 90 x 55 x 40mm DESCRIPTION The R.F. Solutions low cost Wireless Modem provides a reliable serial data communications link that can be used for many data communications applications. The RF Modem is very simple to use and provides an RS232 ‘invisible link’ up to 9600 baud. Each Modem may be configured to be either a ‘Master’ or ‘Slave’ to be used in a wireless network. Up to 127 ‘slaves’ may be controlled by a single ‘Master’ Modem. Packetising and encrypting the data as well as error checking with full acknowledgement for all data transmitted achieve highly reliable communication. The RF Modem is supplied with an RS232 cable to connect the host and requires only a 9-12Vdc power supply. BLOCK DIAGRAM VCC Volatile Mem 9 Way 'D' Type RS-232 MCU FM 433MHz Transceiver TX RX CD Links DS232_2 June 00 ©2000 Reg. No. 227 4001, ENGLAND Page 1 RS232 LOW COST RF MODEM FM-232C-433 FUNCTIONAL DESCRIPTION The RF Modem is designed to connect two DTE devices (e.g. PC’s). The RF Modem physical interface is a 9 pin DCE. The host communications RS232 operates at various baud rates, 8 data bits, 1 stop bit, no parity. The DTE device must either support hardware CTS flow control, XON/XOFF flow control or if hardware flow control is disabled then the user must be aware of the maximum buffer size of 56 bytes. (note: if you use a null Modem to connect a DTE to a DCE using two RF Modems, then the DCE device should support RTS flow control.) LED’s The RF Modem has three LED’s, Tx, Rx, and CD: CD (Carrier Detect). The CD LED will flash on/off for 100 mSecs when a RF connection is active. The flashing status of CD is on a 60 Sec connection timer. After 60 Secs of inactivity the CD LED will automatically extinguish. The CD LED is held on when the RF Modem detects another device transmitting (receiving). This could be its partner, another pair of RF Modems or another RF transmitting device using the same frequency. Tx (Transmit). The Tx LED is illuminated when the RF Modem is currently transmitting an RF packet. Rx (Receive). The Rx LED is illuminated when the RF Modem detects a receive packet which is addressed to that particular RF Modem. POWER SUPPLY The RF Modem requires a 9 - 12V @ 100mA power source. On the power jack the centre is +ve connection. The power switch is a slide switch located on the bottom of the unit. STANDBY MODE When not transmitting, the RF Modem continually searches for a carrier signal and valid I/D address, which match its own. When detected, the RF Modem receives the data, acknowledges back to the transmitting RF Modem and decodes the data before transmitting it out onto the host RS232 port. USER CONFIGURABLE JUMPER LINKS There are several Jumper Links, which the user may set. Please note that these are only read at power up! ECHO / REPEATER MODE (J1) In echo mode each data packet that is received is transmitted out immediately after reception. This may be used to extend the system range. note: In Echo Mode, the RF Modem generates an acknowledge signal to the originating RF Modem. The originating RF Modem will not receive an acknowledge signal from the destination RF Modem if it has been echoed by another RF Modem. J1 Option Open Connected Echo Mode Selected DS232_2 June 00 ©2000 Reg. No. 227 4001, ENGLAND Page 2 RS232 LOW COST RF MODEM FM-232C-433 HOST COMMUNICATION SPEED (J2, J3) The data link between the Modem and the host computer may be set using the appropriate jumper links on the Modem circuit board. It is set according to the following table. J3 Open Open Connected Connected J2 Open Connected Open Connected Baud Rate 1,200 2,400 4,800 9,600 note: The host communication link is ONLY the speed of communications between Modem and the host PC, The radio communications speed is controlled by the two Modems which are communicating which is dependant on many other factors. MASTER / SLAVE SELECTION (J13) J13 Open Connected Option Slave Mode Master Mode MASTER / SLAVE ADDRESS SELECTION (J6-12) Used to set the modem’s address when in master or slave operation Link no Address bit J12 6 (MSB) J11 5 J10 4 J9 3 J8 2 J7 1 J6 0 (LSB) Note: if the address links are set to zero (all address jumper links open) then the modem will be in Broadcast mode (see below for full description) DATA FLOW CONTROL (J4, J5) J4 Connected Open Open J5 Open Connected Open Option Hardware Flow Control (RTS/CTS) XON/XOFF Flow Control No Flow Control J18 - J21 RS232/5V data Input, these jumpers are used to set the data into the modem, either as RS232 data or 5V inverted data. Usually set between pins one and two in all cases to select RS232 data in. DS232_2 June 00 ©2000 Reg. No. 227 4001, ENGLAND Page 3 RS232 LOW COST RF MODEM FM-232C-433 MASTER SLAVE COMMUNCATION When the modems are configured in a master / slave arrangement only the master can initiate communications. If a number of slaves are used within a network (all with different addresses) then the master will need to initiate communications with each slave modem in turn. This can be achieved by changing the address of the master modem from the host controller (see below). Note: If two modems are both set to master with the same address then either modem can initiate communications. TRANSMIT ADDRESS SELECTION There are two methods of selecting the transmit address; 1. Jumper Link Header (JL) - Through the address jumper links. 2. Host Selected (HS) - By host controller to which the Modem is connected. (See below) SENDING A NEW TRANSMIT ADDRESS FROM THE HOST CONTROLLER The host generated address is communicated to the Modem via the standard RS232 data link. In order for the RF Modem to determine that the data being received from the host controller is a new transmit address (and not actual data to be transmitted), a specific command must be sent as below; ZCZCnnnNNNN where ZCZC is the transmit new address start identifier and nnn is the new 3 digit address. and NNNN is the transmit new address end identifier The address is stored in volatile memory and will be lost on power down. If the modem is set to either master or slave then it will read its own address jumper links as a default on power up. This enables point to point communication between two master modems if they both have the same addresses on power up. CLEARING THE CD When using the modems in a master slave situation it might be necessary to clear down the CD between the two modems. This will enable the master to talk to another slave immediately and not have to wait for the 60 seconds until the CD automatically clears down. This is achieved by sending the following string of characters from the master modem via the standard RS232 data link; ZCZCCCCCNNNN BROADCAST MODE Broadcast mode can be used to send data from the master modem to all of the slave modems within range. When the master modem’s address is set to zero it is then in broadcast mode. Broadcast mode is one way communication only and because of this if any of the data is lost in the transmission the slaves will not be able to request the data to be sent again by the master. Note: The CD will only be active for 5 seconds in Broadcast mode DS232_2 June 00 ©2000 Reg. No. 227 4001, ENGLAND Page 4 RS232 LOW COST RF MODEM FM-232C-433 ERROR CHECKING / RELIABILITY Several methods are employed, a. Checksum. b. I/D & COMMAND : bits are sent to on each packet. c. Data Sequencer : this ensures that the receiving Modem knows the logical sequence of packets so that if an ‘acknowledge’ only, was destroyed causing re-transmission of a data packed, the receiver knows this packet has already been received and discards the data. ANTENNA & RF MODEM POSITIONING The helical antenna provided will provide adequate range for most applications. For optimum range, follow these general rules: • • • The space around the antenna is as important as the antenna itself. The optimum position is to locate the antenna so that is protrudes upwards. If this is not possible due to other design constraints, try to keep the antenna away from other potential sources of interference such as transformers, batteries and PCB tracks, especially ground planes. Note: Personal computers are one of the one of the greatest generators of RF interference. Ensure the RF Modem is situated as far away as possible. CE COMPLIANCE This product is a sensitive electronic instrument and as such it may temporarily be affected by Radio Transmitting Devices being used in close proximity to it (such as Mobile Phones, Walkie Talkies, CB Radios, Radio Model Controllers and some Microwave Ovens). If it does exhibit symptoms such as display of erratic or erroneous data, try moving this product away from the source of interference or switching off that source of interference whilst you are using this product. CONNECTION INFORMATION The RF Modem interfaces to the host computer via RS232 connection. A standard DB9 connector as shown in the diagram below. PC Serial Port DTE (DB25) RF Modem DCE (DB9F) 8 1 3 2 2 20 7 6 June 00 4 5 RF Modem DCE (DB9F) 1 1 2 2 Tx 3 3 Rx 4 4 DTR 5 5 GND 6 6 7 7 RTS 8 8 CTS 9 9 Tx Rx DTR GND 6 4 7 RTS 5 8 CTS 22 DS232_2 3 PC Serial Port DTE (DB9) 9 ©2000 Reg. No. 227 4001, ENGLAND Page 5 RS232 LOW COST RF MODEM FM-232C-433 TECHNICAL SPECIFICATIONS Storage Temperature; -10 to +70o Celsius. Operating Temperature; 0 to +55o Celsius. Dimensions: Enclosed products : 90mm x 55mm x 40mm PCB 81mm x 46mm ELECTRICAL CHARACTERISTICS Supply Voltage Supply Current Transmission Frequency Radiated Power (ERP) MIN 9 TYPICAL 12.0 21 433.92 10 MAX 16.0 DIMENSION V mA MHz mW Ordering Information; Part Number FM-232C-433 PSU12V1AUK ICEPIC-PSU-INTL Description nd FM Radio Modem 2 Generation Power Supply 240Vac (12Vdc @1000mA) Power Supply 110-240Vac (9Vdc @750mA) For more information or general enquiries, please contact R. F. Solutions Ltd., Unit 21, Cliffe Industrial Estate, South Street, Lewes, E Sussex, BN8 6JL. England Tel +44 (0)1273 898 000 Fax +44 (0)1273 480 661 Email [email protected] http://www.rfsolutions.co.uk RF Solutions is a member of the Low Power Radio Association All Trademarks acknowledged and remain the property of the respected owners Information contained in this document is believed to be accurate, however no representation or warranty is given and R.F. Solutions Ltd. assumes no liability with respect to the accuracy of such information. Use of R.F.Solutions as critical components in life support systems is not authorised except with express written approval from R.F.Solutions Ltd. DS232_2 June 00 ©2000 Reg. No. 227 4001, ENGLAND Page 6