Problem with aynchronous recption on PIC16F876

[Guest]

My PIC must receive 3 bytes, sent by another one. When I turn the receiver on, If the serial signal has been pluged before, the program Crash...

When I turn the Receiver Pic on with the serail signal pluged, it works good, and then I plug the the serial signal form the other pic, and it works good....

How is it possible to make the receiver works good when turning it ON and plugged ?

I use an #int_rda to launch the recpetion... might it work with a KBHIT ?

[Ttelmah]

This is down to writing the program to handle unexpected events.
Remember that asynchronous serial at the PIC, 'idles high'. I'd suspect that when the other kit is plugged in, and not turned on, the line is being pulled low, so the PIC sees continuous '0' characters, and this then leads to the crash.
Your code should be writen to be able to handle this, since otherwise even after initialisation, patterns like this, could cause problems...
At boot, I'd suggest directly reading the serial receive line, and waiting till it does go high, before starting the main code.

Best Wishes

[Joyce]

You're right, I've done a getc() at the beginning of the main code. It has enabled the receiver module to start well when the other one IS NOT plugged.

The level is still HIGH on the receive pin, because of an amplifier system.

And when the receiver module turns ON, and the signal is arriving on the receive pin, it crashes...

With the debugger window, we saw that it crashes only when doing a the first getc() programm.

I don't what to do actually...

[tojape]

I agree with Ttelmah.
Every communication between two systems may contain corrupted data. You can not, moreover, may not! rely on the assumption that both sides will allways receive error free data. Instead, error handling will be the bigger part of a program section which uses communication.
The simpliest way to avoid the possibility of crashing beacause of corrupted data to form packets from the data stream.
A valid packet always has a header, the payload data, the footer and a checksum. There are a lot of protocols used worldwide for this purpose.
Apart from the approach above, the other cause might be an erroneous behaviour of the getc() function. I am not convinced that it handles frame and overflow errors correctly. Actually, don't use it at all. I wrote an interrupt driven, puffered getc instead.
If you need further information, feel free to contact me.
Best wishes
tojape
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