One of the quirks of the SBC6120-RBC boards I just built is that its serial port talks a protocol that’s very rarely seen these days: 7 bits, mark parity, 1 stop bit. minicom supports it, but seemingly can’t set it from the command line.
Kermit, of course, can. Kermit (not the frog, but named after him) is the connect-to-anything, with-anything comms package. It’s been in constant development since 1981, and there’s hardly a computer system that exists that it won’t run on. The Unix/Linux variant, C-Kermit, has an incredibly intricate hand-crafted makefile that predates autoconf or cmake or any of those newfangled toys. Unfortunately, though, this means it may need a lot of reading and a little hand to compile.
There may be some additional dependencies, but to build a simple version of C-Kermit 9.0.304 Dev.23 on Ubuntu 19.10 and Raspbian Buster you need this patch, and do something like:
tar xvzf cku304-dev23.tar.gz
patch < ckermit-9.0.302-fix_build_with_glibc_2_28_and_earlier.patch
and it should build correctly. There are many, many options: make linux+ssl gives some extra network security features; make install puts it in the system path.
The command line I use to connect to the SBC6120-RBC is:
kermit -l /dev/ttyUSB0 -p m -b 38400 -m none -c
That drops you straight into a connection. To get you back to Kermit’s command mode, type Ctrl + \ + C.