pc to pc communication using rs232 connected through optical link showing FRAMING ERROR

Question

I have set up a PC to PC optical communication link using RS232 Port.

I have used PC1 RS232 -> MAX232A -> Optical Tx/Rx Module -> MAX232A -> RS232 - PC2

sending and receiving data using RealTerm software.

but while sending data from PC1, some another data is received at PC2 stating Framing Error i.e. error in identifying start and stop bit. e.g -
Input | Output
1 | g
2 | 3
3 | f
5 | e
and so on

but for PC1 RS232 -> MAX232A -> COPPER WIRE -> MAX232A -> RS232 - PC2 No error detected and correct value are received.

What could be reason for Framing error in Optical link and - what could be the possible solution for the same?

Answer 1

It's not a complete optical link.. only partial. That being said, you need to ensure that all end points are working. You need to step out the troubleshooting by putting what is commonly called a "loopback plug" at each link. This is an old term that basically means to loop back the signal on the current side of the link without having to worry about the other side you are trying to communicate. Once you have verified each side is working properly without having to talk to each other, try to integrate the two links. If it still does not work, then you know the problem is between the two optical link modules. If your settings match your devices settings, and you are still receiving a framing error, you may be experiencing noise on your serial line.

Not knowing anything about your configuration or type of hardware, it is hard to say exactly what parameters you have flipped or incorrect.

Answer 2

The error is being produced in one of the RS232 links where both sides are configured with different parameters. Verify that speed, parity, 7 or 8 bits and stop bits are the same in both sides of the RS232 connections.