Setup serial connection for remote KVM

I’ve got a TrueNAS Core NAS that will be a remote backup system for my main TrueNAS instance. I will be configuring a somewhat complicated networking scheme, so I’m trying to setup a Raspberry Pi as a basic KVM, communicating with TrueNAS over a serial connection.

The backup NAS uses an ODroid H3 and I’m having trouble reading messages over the serial port (via GPIO pins). To test this out, I want to connect to the serial console from a TrueNAS shell before moving on to the Raspberry Pi. Try as I might, I’m not able to read serial messages. Here are the relevant settings I’ve changed:

  • System / Advanced / Enable Serial Console (checked)
  • System / Advanced / Serial Port (0x3f8)
  • System / Advanced / Serial Speed (9600)

The command I tried was cu -l /dev/ttyu0 which resulted in just a bunch of junk characters being printed.

What am I doing wrong? Does the serial console not provide a text console?