I don’t know how many years I’ve used ckermit as trusted terminal emulator and just carried along the same .kermrc (probably initially copied from the DULG):

set line /dev/devcon
set speed 115200
set carrier-watch off
set handshake none
set flow-control none
robust
set file type bin
set file name lit
set rec pack 1000
set send pack 1000
set window 5

However with debian testing, ckermit is not available anymore, and before compiling from source, I did a quick search for an alternative. This turned up picocom, a “minimal dumb-terminal emulation program”, which works nicely. The following one-liner replaces the .kermrc above:

picocom --escape=z --baud=115000 --parity=none \
        --databits=8 --stopbits=1 --flow=none /dev/devcon

The --escape=z sets the escape sequence to Ctrl-z, so you can exit by typing Ctrl-z followed by Ctrl-q.