Wireless RS232 & RS485 Data Links

The ELPRO 805U radio modem module provides RS232 or RS485 connections by radio. It can be used instead of serial cable to link PLC's, data loggers, supervisory computers and intelligent transducers. The 805U has been designed to be easy to use and simple to install. It uses a low power 868MHz radio which does not require a radio licence in most European countries. The module is fully integrated with radio, power supply, serial ports and microprocessor controller housed in a strong industrial aluminium case.

Simple and Reliable 
The 805U includes a radio transceiver, allowing communications in both directions, so the modules can check and control the transfer of information. The 805U is suitable for both simple and complex systems. It can operate in a transparent mode, where the host devices provide error checking and communications control. For less intelligent host devices, the 805U can provide the addressing, error checking and control of communications. The 805U can also accept Hayes compatible commands for selective addressing.
 
High Speed Wireless Data
Host devices can connect to the 805U via RS232 or RS485 serial ports, at data rates up to 115.2 Kb. The 805U has an internal buffer of 2 Kbytes, and the radio can transmit data packages of up to 530  bytes, at speeds configurable up to 76,800 bits/sec. The 805U radio modem is both low cost and very flexible.
Radio Communications
The 805U operates in the 868 MHz UHF band.  The 805U radio is available with transmit power of 500mW, and meets CE radio regulations. The 805U has been designed to operate reliably on an open channel with other users.

The maximum radio range of the 805U is 5 km line-of-sight with unity gain antennas.  The 805U module may also be configured to act as an intermediate repeater to provide longer radio paths.  In controlled mode, up to five repeater modules may be configured for each link, and in transparent mode, an unlimited number of repeater modules may be configured for each link.

The transmission rate of the 805Uradio may be configured between 19200 and 76800 bits/sec, half-duplex.

RS232/485 
The 805U connects to host devices using RS232 full duplex or R5485 half duplex. The RS232 connection provides standard CTS/RTS control, with the 805U module operating as a DCE device. The CTS/RTS signals may be configured to reflect the status of the 805U input buffer, or to reflect the CT5/RTS signals at the remote module. The R5485 connection is a industry standard half-duplex twisted pair mulitdrop connection. Only one serial connection (R5232 or RS485) can be supported at each module,however different types of serial data can be connected to different modules in the same system.

The 805U accepts data at standard rates between 1,200 and 115,200 baud. It may be configured to accept 10-bit or 11-bit characters, with 7 or 8 data bits, even/odd/no parity, and 1or 2 start and stop bits. The 805U will connect to almost any host device!

Configuration
The 805U module may be configured to operate in two different modes, to suit the type of host device. In each mode, data is sent in packets of up to 530 bytes, with a superimposed "system address". Only a module with the same system address will accept data from another module - this avoids cross-talk between systems operating in the same radio range. Modules may be configured manually or by the host device using standard Hayes codes.

Transparent Mode
Transparent mode is suitable for host devices which provide their own data checking and control the flow of data. As data is received at the serial port, it is transmitted by radio and re-created at the serial port of all other modules with the same system address.There is no error checking carried out by the 805U modules and modules are not individually addressed - this is performed by the host devices.  Modules listen to the radio channel and hold off transmitting until the channel is clear, apart from this there is no other transmission delay. Transparent mode is suitable for PLC networks, or for a broadcast system where the same serial data is to be sent to multiple devices. In transparent mode, one repeater may be configured - the repeater will re-transmit any radio message it receives.

Controlled Mode 
In controlled mode, each module is configured with a unit address, and the 805U modules perform error checking and acknowledgments. If a message is corrupted during the radio transmission, the source module will re-transmit the data up to four times until the data is received correctly. If reliable radio communications cannot be achieved, a communications failure output is provided as a discrete signal. Controlled mode is suitable for host devices such as data loggers or intelligent transducers which do not carry out error checking or control the flow of data. In controlled mode, up to five intermediate repeaters may be configured in any one link. Destination addresses, and repeater messages may be preset using the configuration switches on the module, or they may be set from the host device using standard Hayes AT codes. This type of system would be suitable for a master device (such as a PC) polling several slave devices (for example, data loggers) to download information.

Specifications

Power Supply

• The 805U module may be powered from either a 10 - 30 VDC or 10 - 24 VAC supply
• Normal current drain 70mA (@12VDC) or 50mA (@24VDC)
• Current when transmitting 350mA (@12V), 250mA (@ 24V).
• Low power mode,  normal current drain is 20mA (@ 12VDC),  15mA (@24VDC)

General 

• Environmental -30 to 60 degC (full performance),  -40 to 70 degC (typical performance)
• 0 to 99 %RH 
• EMC Compliant ETS 300 683
• Housing, extruded aluminium case 114 x 185 x 30 mm DIN rail mounting, removable terminal blocks for ease of module replacement, terminals suitable for 2.5sqmm conductors.
• LED indication for unit OK, radio TX and RX, serial TX and RX, DCD (comms OK).

Serial Port

• Standard data rates 1200 to 115200 baud.
• RS232 and RS485 standard interface connections provided, each connected to the same serial port. Serial interfaces are asynchronous non-return-zero (NRZ) format.
• The following characters are supported (selectable) - 7 data bits, even or odd parity,1 start bit,1 or 2 stop bits; 7 data bits, no parity,1 start bit, 2 stop bits; 8 data bits, even or odd or no parity, 1 start bit,1 stop bit
• RS232 connection provides full duplex operation as a DCE device with RTS/CTS hardware handshaking- standard D9 connector.
• RS485 connection provides half duplex operation for twisted-pair multidrop networks.
• Terminal connectors provided for RS485.

Radio Transceiver

• Single channel,  synthesised transceiver
• Frequency 869.4 - 869.65 MHz,  250KHz channel
• Transmit Power 500mW
• RSSI -60 to -120 dBm RF Data Transmission Rate - 19200 baud, 38400 baud, 76800 baud
• Range may be extended by:-
  - up to five intermediate repeaters for controlled mode
  - unlimited repeaters for transparent mode 
• Conforms to EN 300 220 Antenna connection is SMA coaxial

Data Transmission

• Transparent mode: Data is transmitted with a system address
• Data transmission begins as soon as serial data is received.
• For RS232, DCD signal is always high, and CTS is high while there is space in the input buffer.
• All modules, with correct system address, which receive the data packets, output the data without error checking.
• Controlled mode: Data is transmitted in packets of up to 520 bytes (configurable), with a system address, source address, destination address, up to five intermediate repeater addresses, and a 16 bit CRC error check.
• If the packet is received with a correct error check, only the destination module will output the data and will also return an ACK transmission.
• If the source module does not receive the ACK, it will retry a further four times before resetting the DCD output.
• For RS232, the CTS signal is high if there is room in the input buffer.
• Destination and repeater addresses may be configured using Hayes AT commands.