Anyone else's UART RX (serial input) stopped working?
I installed and was happily running OpenBSD on my RockPro64 v2.1 for many months. At some point I needed to wipe and reinstall everything. When I attached the serial console as usual, I realized that I was only ever able to get serial output FROM the board, but was no longer ever able to send any serial TO the board.

I have performed all of the expected troubleshooting steps many, many times to figure out what the heck I'm doing wrong:
  • rechecked TX, RX, and GND connections
  • rechecked serial terminal baudrate and settings (correct because I'm getting good serial output)
  • swapped out different FTDI USB-serial cables
  • confirmed I was able to use the same FTDI cable to send and receive on a different SBC
  • connected both TX and RX lines to an oscilloscope (with serial decoding) to monitor that I was, indeed, sending and receiving valid serial data to/from the board

At this point I'm starting to think that I must either have inadvertently shorted the UART RX pin to something bad and blown the OC/OV/ESD protection in the silicon, or maybe there is even a manufacturing defect.

As my next debugging step I was going to start writing firmware to manually read the RX pin and see if it picks up signal changes, but I wanted to check with folks here and see if anyone has encountered this and/or if someone can suggest an easier debugging strategy.

Thanks much!

Messages In This Thread
Anyone else's UART RX (serial input) stopped working? - by pion - 03-23-2022, 02:02 AM

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