Posted: Mon Apr 09, 2012 1:02 pm Post subject: Problem with RS-232 interfacing
Hey guys. I have a problem with interfacing my bluetooth module (aubtm-20) with Atmega 640. The BT module works perfectly and responds to the commands sent when connected directly to a PC. I have also debugged the code and it works perfectly. But when I connect the BT module (Rx and Tx pins are connected to MAX232 and then to DB9 connector) to the microcontroller using DB9 connector + MAX232, I get incomplete response.
For example, instead of getting getting the response as "<CR><LF>OK<CR><LF>", I get a response like "<CR><LF>O<LF><CR><LF>". The response I get seems to be a part of the actual response but I get a different response everytime.
Rx of BT module is connected to Tx of microcontroller and Tx of BT module is connected to Rx of microcontroller.
I also have shorted grounds of both the boards and have ensured that the baud rates are proper.
Hard to tell without the code and any other info.
Did you check the status report to see the %-deviation of the com?
Sometimes setting the internal pull-up on RX helps.
Hubert
edit: What you post looks like a character overrun.
Mostly happens if you spend too much time in an ISR.
Do you use serial buffer or polling...bytematch....???
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