I use a simple rf module to communicate PC and pic 16F877. I send characters and I receive different characters than I have send. But I take same wrong value for the same cahracters altough it is wrong. What can be the problem?
Make sure that bytes (characters) at both ends are in the sampe phase .. ie. if you send a "1" you should receive a "1" .. not a "0" (RS-232 drivers invert signal's phase, so if you use them, and computer port does, use them at both ends) ..
Next thing, check out if both ends use the same word structure (for example, 8bits, 1start, 1stop, no-parity) and baud rate ..