communication with AVR microcontroller

Posted on Feb 5, 2014

The TRW-24G connector pins is 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, andnot on pin order of the module`s connector. My circuit is constituted by 2x TRW-24G modules, 1x AT90S2313 microcontroller

communication with AVR microcontroller
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and 1x MAX202 TTL to RS232 voltage level converter. The RF modules work with +3. 3V not with +5V. I connected 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 works at +5V power supply. There is no problem with that, but the AT90S2313 MUST 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 AVRwill configure the IC1 as receiver and IC3 as transmitter. Then, the AVR will check the DR1 pin of IC1 for incomming data. If DR1 pin of IC1 is LOW (logic `0`) the AVR will send serially fromIC3the 5 byte address of the module that wants to send the data (AA, BB, CC, DD, EE hex address) and the Payload bytes which is the data thatwants to send (31, 32, 33, 34 hex, arethe same as 1, 2, 3, 4 ASCII). When AVR pushes the CE1 pin of IC3 to LOW (`0`) the IC3 transmits the data with baud rate of 250kbps (I set the communication to 250Kbps not to 1Mbps). After some small delay, the AVR reads again the DR1 pin of IC1 for incoming data. In this step the DR1 pin of IC1 goesto logic `1` because receiver`s buffer now has the4 bytes (payload bytes) that we had transmitted before with IC3. The LED1 it will flash for a moment to show that the receiver`s buffer has incoming data. Then, the AVRwill read these 4 bytes and send them...

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