SERIN2 Receiving Wrong Data

[rsocor01]

Hi, I have two devices communicating with SERIN2/SEROUT2. Device A, a PIC18F4550, sends data to device B a PIC16F19197. I'm receiving the data at device B using SERIN2, but like 1 out of 5 times I receive a wrong byte. I know that device A is sending the correct data because I can see the right data with my logical analyzer. So, the problem is with SERIN2.

I placed a 10k resistor in series to prevent either device to send power to the other device when one of them is turned off. Do you think that this resistor is the problem?

'Code at device B, PIC18F4550
SEROUT2 PORTB.7,32,[STR RFID_IN\7]

'Code at device B, PIC16F19197
SERIN2 PORTE.1, 32, 5, BOARDSEARCHFAILED, [STR ClockInDataArray\7]

[Ioannis]

Yes it could be a problem. Try with no resistor and see if the problem is in your code or just the lack of power on the link. Then try max 1K resistor.

But without more details like, type of cable, length and most important your code on both PIC chips, it is not easy to address the issue.

Ioannis

[HenrikOlsson]

Are these PICs on the same PCB or on each end of a long cable?
Cable (well PCB traces too of course) has capacitance, with a 10k resistor you're forming quite an RC-filter (relatively speaking) which slows down the rise and fall times of the signals.

If you have a scope, compare the signal on the sending and receiving PICs respectively.

[tumbleweed]

Another thing that could be causing problems is that SEROUT2/SERIN2 are software bit-banged (no hdw UART involved),
so device B must be sitting waiting at the SERIN2 for the first start bit before device A begins transmitting, else the timing won't be correct.

[rsocor01]

I tried removing the 10k resistor and I'm still having the same problem. The PICs are in two different PCB boards. The serial communication is taking place over a 3ft cable. The cable has 2.5mm mono plugs connectors at the end. I'm using a Baud rate of 19200. I'm going to try 9600 to see if that helps.

Each PIC has thousands of lines in code. I don't think there is a problem with the side sending the data because I can see the correct byte with the logical analyzer. The issue in in the receiving end.

[Ioannis]

Your best shot would be to post your code...

Ioannis