No activity on IO Debug port for Pixhawk 4 fmu-v5

I am looking to read PX4_ERR messages and assume I would read them over the IO Debug port on the side of my Pixhawk 4. I hooked pin 4 (pixhawk tx) and pin 5 (pixhawk rx) to an oscilloscope and saw no activity with tx reading high and rx reading low. When I connected it to the computer with an ftdi adapter and putty I could see keyboard strikes on rx but still no activity on tx. Is there something I need to do to activate debugging?

I assume you want to debug PX4_ERR “printfs” of the FMU side (not IO side)? In that case you need to connect the FTDI adapter (or Dronecode Debug probe) to the “FMU Debug” port.

Thanks I am getting some messages now.

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