Original instruction for Windows: https://groups.io/g/ninotnc/message/204
Set the baud for the device:
~$ stty 57600 -F /dev/ttyACM0
Send the following command to the device:
$ echo -ne '\xC0\x0C\xC0' > /dev/ttyACM0
Check the reponse:
~$ cat -v < /dev/ttyACM0
M-@M-`2.35-@^C^C
Good, looks like the TNC is working with version 2.35 of the firmware.