Communication of TRW-24G RF modules with AT90S2313 microcontroller

Introduction

My first attempt with RF modules was with TLP and RLP418 modules. Those modules working at 418 MHz with slow data-rate (typical 4.8 kbits/sec) and every module is transmit or receive only. TLP418 is only transmitting data and RLP418 module is only receive data. You can not make a bi-directional communication with only one couple of this modules. The solution of this problem is the use of TRW-24G transceiver modules (transceiver = transmitter + receiver). This modules working at 2.4 GHz frequency with GFSK modulation, and the data-rate is 250Kbps and 1Mbps (1 mega bit/second!)

description

First of all I would like to say that the TRW-24G connector pins are too small (~1mm pin to pin). For that I order the adaptor PCB that is convert the small connector of RF module, to standard pin connector. The pin order of RF modules in schematic diagram is based on pin order of pin adaptor, and not on pin order of the module’s connector.

My circuit is constituted by 2x TRW-24G modules, 1x AT90S2313 microcontroller and 1x MAX202 TTL to RS232 voltage level converter. The RF modules work with +3.3V not with +5V. I connect this modules to STK500 development board and I set the VTG voltage to 3.3V from programmer’s software in AVRstudio. For serial communication I used the internal MAX202 of STK500 board, that is working at +5V power supply. There is no problem with that, but the AT90S2313 MUST be work at 3.3V or else you will burn the RF modules if you send +5V instead +3.3V (max. 3.6V).

When you power-on this circuit, the AVR it will configure the IC1 as receiver and IC3 as transmitter. Then, the AVR it will check the DR1 pin of IC1 for incomming data. If DR1 pin of IC1 is LOW (logic ’0′) the AVR it will send serial from IC3 the 5 byte address of the module that is want to send the data (AA,BB,CC,DD,EE hex address) and the Payload bytes wich is the data that it want to send (31,32,33,34 hex, are the same as 1,2,3,4 ASCII). When AVR push the CE1 pin of IC3 to LOW (’0′) the IC3 transmitt the data with baud rate of 250kbps (i set the communication to 250Kbps not to 1Mbps). After some small delay, the AVR is going to read again the DR1 pin of IC1 for incomming data. In this step the DR1 pin of IC1 is going to logic ’1′ because receiver’s buffer now have the 4 bytes (payload bytes) that we have transmit before with IC3. The LED1 it will flash for a moment to show that the receiver’s buffer have incomming data. Then, the AVR it will read this 4 bytes and send them serial via PD1 and MAX202 to PC with baud rate 9600bps/8/n/1. When AVR read all data from IC1, the LED1 it will turn-off.

You can connect the CN1 to COM1 serial port of your PC, run the Hyperterminal (start->programs->accesories->communications->hyperterminal) and set it at COM1 with 9600bps/8/N/1. When you power-on this circuit you will see some small flash in the LED1 and after a small delay you can see the ASCII characters <1234> in Hyperterminal’s screen.

>> Schematic of the electronic circuit.

The TRW-24G modules are transmitters and receivers both. The function is dependent by the configuration of each module. When you power-on the module, you have to send 2 or 16 serial bytes to configure the modules. The method to configure this RF modules is described in this manual.

Another great tool for Windows, to make the configuration file of 16 bytes, is nRF Configuration Word Generator and is created by Michael Mittermayr.

• Download the schematic, hex and source code in assembly, of this project.

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source http://www.serasidis.gr/