Test uart at low baudrate fail at bit 8, linux

Question

I'm testing between 2 uart RS485 port at low baud rate, 600bps, 1200bps.

The first round (uart 1 to uart 2) is always accurate. However, the second round (uart 2 to uart 1) is sometimes wrong at bit 8 (I send char, hopefully bit 8 is 0 (initialization is 0 for every bit in sent data) but catching data at bit 8 is 1). For eg.

send 0x00, receive 0x00

send 0x00, receive 0x80

...

High baud rate (>= 9600) transmission have't have any issue.

Did you used to face same issue before?

Answer 1

Maybe you can describe a bit better your setup, in particular the hardware side.

From the errors you're getting at low speed only I would say there might be something wrong with the flow control line (drive enable/~read enable). It would help if you have the chance to monitor your bus with a scope. If you do and you can post a couple of snapshots maybe I can offer more help.