CDX800 DESCRIPTION
2.4. Description of the individual parts of the CDX 800
2.4.1.
Radio module
The radio transceiver XBee has been used for wireless communication on the radio
channel. The module achieves high-rate parameters thanks to used digitalization of both
the transmitter and receiver. The modem works in the band 869 MHz. For usage within
specific regions, restrictions as to the frequency selection are provided to comply with the
appropriate legislation. The transmitter works with the OFDM modulation; the transmitting
power output can be programmed in steps of 1 mW up to 315 mW. The maximum
transmission rate is 24 kb/s with duty cycle receiving/transmitting 10:1.
The duty cycle is according to the ERC/REC 70-03 document.
2.4.2.
Control microprocessor
Thirty-two-bit microprocessor Freescale Coldfire with 512 kByte FLASH EEPROM
memory and real-time circuit with reserve power supply makes for the basis of CDX 800
control microprocessor. Software is based on real-time operating system that processes
simultaneous tasks. Thus parallel operation of all external interfaces of the communication
module is maintained.
The microprocessor is connected through the synchronous serial interface to the radio
component and controls the communication via the radio channel. Towards a user it
connected on serial interfaces, typically RS232, and direct I/O signal processing circuits.
The microprocessor enables connection of up to two user devices through two serial
interfaces. The ports are linked to RJ45 connectors marked PORT1, PORT2. All user interface
signals are protected against over voltage on the data cable.
Device with different communication protocol can be connected to each interface.
The microprocessor may work as a protocol converter between separate serial user interfaces.
The wide scale of CDX 800 module features can be configured through any RS232 serial user
interface using service software.
In case other than RS232 interface device needs to be connected, e.g. RS485/422, it is
possible to connect level converter to the serial port according to particular application.
The microprocessor can control such external converter.
The microprocessor further manages numerous functions of servicing, diagnostic
and installation purposes. The computer saves various information such as GPRS data
communication statistics, ports activity, power failure, voltage of backup power source
and temperature inside the CDX 800 module to its memory.
Configuration of the CDX 800 module is stored in the FLASH EEPROM memory.
The RADWIN service software has been designed for setting of the CDX 800 modem
configuration. The description of program RADWIN is in reference
[3]
.
2.4.3.
Inputs and outputs for telemetry
Apart from serial data interfaces there is CIO interface established in the module.
These are 5 signals to be used as analogue or binary inputs or binary outputs with an open
collector. The input can be analogue 0 - 5 V or digital with control level adjustment. The output
is an open collector able to switch up to 500 mA. Reading and control of I/O signals is possible
from the remote CDX 800 module or any serial user interface. Two CDX 800 modules can
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