RMX232 Radio Modem User’s Guide N11391 Embedded Communications Systems Specialists in Embedded RF Data Communications, Monitoring and Control Systems
Copyright Notice Copyright ©2006 by Embedded Communications Systems Pty Ltd. All rights reserved. Under the copyright laws, this manual cannot be reproduced in any form without the prior written permission of Embedded Communications Systems. No patent liability is assumed, with respect to the use of the information contained herein. embeddedcomms RMX232 Radio Modem User’s Guide First Edition November 2006 (Covers firmware version 1.00a) Disclaimer This manual has been validated and reviewed for accuracy.
Contents Chapter 1 Introduction .......................................................................................................1-1 About this Manual ..............................................................................................................1-1 The RMX232 Radio Modem ..............................................................................................1-1 Features................................................................................................................
Chapter 5 Connecting the Radio Modem..........................................................................5-1 Serial Pinouts.....................................................................................................................5-1 Connecting to a PC............................................................................................................5-2 Two Wire Simplex Interface ...............................................................................................
Chapter 1 Introduction About this Manual This manual has been written for the RMX232 range of low cost short range modems license exempt radio modems. A list of the Radio Modems currently covered by this manual is included in the appendix: The generic reference of RMX232 will be used throughout this manual when referring to any one of the RMX232-xxx modem variants mentioned above. Specific information relating to a specific radio modem type will be noted by using the full radio modem name.
Point-to-Multipoint Configuration and Broadcast Multi-drop Configuration Point-to-Multipoint Radio Link RMX232 RS232 c:\ RMX232 RMX23 2 RS232 RS232 Master Unit RMX232 RS232 Point-to-Point Configuration Point-to-Point Radio Link c:\ RMX232 Local Host RMX232 RS232 RS232 Remote Host Features • • • • • • • • • • • • User’s Guide Acknowledged Point-to-Point and Point-to-Multipoint RF networks.
Chapter 2 Installation and Operation This chapter describes basic connection procedures and operation. It also covers the front panel indicator lights and physical mounting and positioning of the radio modem. Serial Interface The RMX232 radio modem interfaces to external DTE equipment using a 9 way D type female connector. The serial interface is configured as DCE equipment with the pin out shown in the table below.
The Radio Modem is fitted with a DC power socket for use with an external regulated 7-15VDC power source. The diagram below shows the power socket polarity. Power socket type and polarity. Contact your distributor if you require an appropriate regulated mains power supply to suit. Starting your computer Switch your computer on if it is not already running, and start your favorite communications application (such as Hyperteminal for Windows).
The status LED indicator on the front of the radio modem should be showing 1 short pulse every 2 seconds (approximately). This indicates the radio modem is in standby mode. The receive LED indicator (green) will also be flashing regularly indicating it is listening for radio transmissions. Sending Serial Data Assuming both radio modems are connected and operating correctly, you are now ready to send some data. Ensure the two radio modems are spaced with at least 5 or more metres between them.
Positioning the Radio Modem In order to achieve maximum operational reliability and range from your radio modems it is important to reduce the possible effects of RF interference on them. Each radio modem has an antenna protruding from the top of the case. This antenna is used for both receiving and transmitting data. This antenna will provide adequate range and reliability for most applications.
problems. Inadequate performance from the bench test may require fine tuning of the configuration parameters. It is recommended that for any new site installation a radio site test be performed. This can be accomplished using the ping and radar diagnostic functions built in to the Radio Modem. The diagnostic functions are explained in detail later. If an installed system exhibits poor performance, both the radio path and possible interference sources should be checked.
Chapter 3 Configuration Commands This section describes the configuration and test commands supported by the radio modem. In most cases, once the configuration is set it will not need to be changed. Configuration is performed using a serial terminal, organiser, PDA or appropriate communication application. All commands and command values accepted by the radio modem are described in this section; any entries other than those listed here results in an invalid command or argument error message.
Configuration Commands in Detail help Display basic help information This command is used to display brief help information. For detailed help information the manual should always be consulted! exit Exit configurator This command exits the radio modem configuration mode and returns it to the data transfer mode. A soft reset of the modem occurs when returning to the data transfer mode, after which the updated settings will take immediate effect.
baud DTE baud rate This command sets the host interface (DTE) baud rate. The changed baud rate will take effect after leaving the configurator using the exit command. Using a DTE baud rate, with no flow control, greater than the radio through-put, you should be aware of the 96 byte serial internal receive buffer of the radio modem. If the internal serial receive buffer overflows then data will be lost. If hardware flow control is used, no data will be lost.
Command format: unit [n] where: n = [0-15] The unit address that a modem pair must be set to in order for them to communicate. site Radio Modem site address This command sets the device site code. Each site code can effectively support up to 16 different unit addresses. For two radio modems to communicate they must have matching unit and site codes.
addr Updates local memory unit, site and hop values This command sets the RAM based values for the unit address, site code and optionally the hop count. The command is provided in order to support continual programmatic changing of the unit address, site code and hop count in an acknowledged point-tomultipoint system. The command, if used without parameters results in an argument error. Entering valid parameters results in a period (“.
dtr DTR Control This command interprets how the radio modem responds to the state of the DTR signal and changes to the DTR signal. If the host device (DTE) interface does not provide a DTR signal then this setting should always be set to off. When DTR control is set to on and the DTR signal is not active, the Radio Modem enters a power saving shutdown state. Upon the DTR signal becoming active, the Radio Modem will power up, perform a reset and be ready to receive data.
dlytx Delay data packet transmissions This command is used to set the delay between the last serial character received by the radio modem and the next packet of data sent from the radio modem. Radio network traffic is reduced by delaying packet transmissions until there is either a timeout of this delay period or there is enough data in the serial receive queue to transmit a complete full length data packet.
cmdchr Configuration escape character and guard time (user defined) This command allows the user to specify the ASCII value used for an escape sequence, and the pause time either side of the escape sequence. The default escape character is the ‘+’ symbol (ASCII 43). The default guard time is 1 second. The guard time (second parameter) does not need to be specified if only changing the escape character.
remote Remote unit configuration This command is used to either enable or disable the unit for remote configuration access. Once enabled for remote configuration access, the radio modem can be configured remotely by another radio modem using this command. Command format: remote [s] where: s = on Enable remote configuration access to this modem. off Disable remote configuration access to this modem. Any remote configuration requests to this modem will be ignored.
rptmode Repeater mode This command enables or disables repeater mode. Please refer to chapter 4 for a detailed overview of the radio modem in repeater mode. Note that the repeater mode takes precedence over mode setting of ptpmode.
seropt DTE serial options This command enables the user to select from several serial protocol options. Command format: ping [s] where: s = 8n1 Sets 8 data, no parity and 1 stop bit. 8n2 Sets 8 data, no parity and 2 stop bits. 8o1 Sets 8 data, odd parity and 1 stop bit. 8e1 Sets 8 data, even parity and 1 stop bit. Upon receipt of serial characters, the modem strips the parity bit, sends the data to the remote device where the parity bit is regenerated if parity is enabled at the remote.
Chapter 4 Modem Operation Explained This section describes in detail the operation of a number of the radio modem’s configurable features. Flow Control The buffers in the radio modem and its flow control function permit serial communications even if the speed differs between the computer (DTE) and the modem DCE or between the radio modems (modem ports).
The radio modem provides three kinds of serial port flow control: hardware (RTS/CTS), software (XON/XOFF) and none. XON/XOFF Flow Control (Software) This type of flow control is performed by sending XON and XOFF control codes in the data stream. The XOFF code makes a transmission halt request, while the XON code makes a transmission restart request. Since these two codes, XON and XOFF, are used as flow control characters, binary data that has these codes cannot be transmitted or received.
Radio Modem Addressing Scheme The RMX232 radio modem provides a two tier addressing scheme applied to each outgoing packet of data. Seven data bits are used by the radio modem for data packet addressing, these being divided into a 3 bit site code (8 possible sites) and a 4 bit unit address (16 possible unit pairs). Addressing Scheme: Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Point-to-Point Addressing: Site/Unit N/A Site Code. 3 Bit Unit Addr. 4 bit Point-to-Multipoint Addressing: 0 - 127.
On-Air Data Speed In a network of multiple radio modem point-to-point links, where network usage is at moderate levels, a situation occurs which results in each pair competing for air-time to transmit its data. The RMX232 enables user selectable throughput rates for the radio interface ranging from 600bps to 9600 bps (2400 bps for RMX232-151/173), thus improving network access.. The on-air data speed varies the amount of airtime a radio modem uses to send data thus directly affecting the throughput.
DTR Power Control The RMX232 radio modem has three states of operation in terms of power consumption. Maximum power consumption within the radio modem occurs during data transfer. A short period after the data transfer has ended the radio modem enters a standby state whereby power consumption is more than halved. To resume normal data transfer again the radio modem either sends a wake up message, or receives a wakeup message, which upon receipt, effectively takes the radio modem out of its standby state.
A receiving modem, upon receipt of a connect request, will send a connect acknowledgement to complete the link establishment phase. Once the communications link has been set up, data can then be exchanged between the Radio Modems. After no activity between the Radio Modems for a short period, both modems send a disconnect request message.
number of attempts an ACK message is still not received the link connection is effectively terminated and the data packet is discarded. The default setting for the number of data packet retry attempts is usually adequate for most situations. However if the radio modems are being used in an RF noisy environment or an environment prone to short signal interruptions (trucks passing between the link, etc) thus resulting in lost data, then the number of packet retry attempts should be increased slightly.
Broadcast Multidrop This mode of operation is determined by the configuration command keyword ptpmode being set to OFF. Broadcast multidrop mode provides a mechanism for building very large networks using the RMX232 radio modem combined with intelligent host controllers. In broadcast multidrop mode, the radio mode does not implement network layer functionality related to data packet routing, acknowledgement and retries. It merely provides an error free mechanism for transferring data between multiple nodes.
Repeater Mode This mode of operation is determined by the configuration command keyword rptmode being set to ON or ALL. Repeater mode takes precedence over the setting of ptpmode. Note that the RMX232-151/173 only supports a maximum of 1 repeater hop. In repeater mode the radio modem becomes a dedicated packet repeater node. Using a number of repeater nodes effectively enables a network to be extended beyond the operating range of an individual radio modem pair.
A receiving radio modem will only accept a data packet whose hop count is zero. It is therefore essential that the correct hop count be specified in the modem configuration for the number of expected repeater hops. With rptmode being set to ALL, the repeater will retransmit all packets regardless of the site address, provided the hop count for that packet is greater than or equal to 1.
Using the Radar function, a site test can be performed by placing one Radio Modem in a fixed position, then walking around the site with the second radio modem. It is best that the mobile unit be connected to laptop or PDA on which the radar test is run. The results are then immediately accessible while you are wandering around the site. A radio modem range test can also be performed in a similar fashion to the site test.
Chapter 5 Connecting the Radio Modem This section details the radio modem serial pin connections and describes various examples of connecting the radio modem to real world devices. Serial Pinouts The RMX232 DTE interface is via a 9 way female D type connector fitted to the side of the radio modem. The DTR signal into the Radio Modem is used to wake up the Radio Modem. The Radio Modem can be forced into a permanently power up state by disabling DTR control in the configurator.
Connecting to a PC To connect the radio modem to a personal computer use the 9 way modem cables supplied. If the computer has a 25 way connector then the use of a suitable 25 way to 9 way adapter should be used. Note the remaining RS232 signals are not connected internally in the RMX232 radio modem.
Two Wire Simplex Interface The radio modem can be used in a very basic two wire simplex connection. In this example, with no wake-up signal provided by DTR the Radio Modem is required to be permanently powered up. This is achieved by setting DTR control to off in the Radio Modem configurator.
Connecting to other DTE and DCE Equipment For DCE and DTE equipment that require DCD and DSR be connected for proper operation, the following interface can be used. Note that the supplied serial cable does not provide the connections shown in the following diagrams.
Chapter 6 Specifications General Radio Approvals Australian Standards AS4268.2 European Standards EN 300 220-3 & EN 301 489-3 Enclosure Extruded Aluminium Optional TS35 DIN rail mounting bracket Interface Connectors RS232 Interface 9 way female D style configured as a DCE RS232 Signals RXD, TXD, RTS, CTS, DTR, GND Power-down control Via DTR (software selectable) Power Interface 2.
Current Drain at 9V Transmit/Receive Average 40mA TBD for RMX232-151P & RMX232-433P Standby 15mA 400uA In power down state Radio Transceiver General Single channel SAW controlled FM transmitter Can also be supplied as a crystal controlled radio module Double conversion FM superhet receiver Fully screening radio modules Receiver Sensitivity -100 dBm for 1ppm BER Antenna Female SMA gold plated antenna connector Impedance 50 ohms Ordering Information User’s Guide RMX232-151.
Chapter 7 Product Version Information Version Information The RMX232 products contain both a hardware and firmware version string. The firmware version information provides some information regarding compatibility with other firmware versions. The firmware version number is displayed both with the signon message and upon entering the command line configurator. The hardware version string provides some information regarding the hardware platform. It contains no useful information for the user.
Chapter 8 Modification History Bug Fixes & Change History Version 2.00a First release of the RMX232 Radio Modem. The RMX232 has been ported from the original RM-232 radio modem, thus all issues and bug fixes have been ported and included in this release of the RMX232.
User’s Guide
User’s Guide
