I am re-posting this issue since there hasnt been any updated from Cypress in over 4 weeks.
I am using PSOC6 to communicate with a controller board over UART. using RS422 driver. The message length is about 300 bytes sent every 100 milliseconds. The issue is every few messages I get extra bytes (1 to 3 bytes) the extra bytes are 0xFF.
Any Idea what what might be causing this behavior?
Make sure that you are not turning off (three-stating) your 422 driver. Some 422 receivers are very noise-sensitive when their differential inputs are floating. And make sure that you are not turning the input to the 422 driver (the TTL pin from your PSoC UART) to high-Z either. Or if you do, make sure you have an appropriate pullup or pulldown resistor on it to maintain a known level. And make sure that your 422 receiver is properly terminated - some require a 100 ohm resistor across the differential input, some have that built in to the chip. (Actually, I think the driver should also be terminated, check the data sheet.)
Is the message always the same length, or does it vary? Is it possible that sometimes the message is shorter but you are sending the same number of bytes? (So you overrun the buffer.)