Nice find . Unfortunately, it still didn't work (random characters being printed). I'll probably need to look into the source of some of these programs to work out what's happening. The 'connect' command shouldn't be influenced by any g-code / x3g issues right; given that it is just arduino C code?

Anyway I'll try some more stuff with Arduino's serial monitor and maybe look at the Sailfish documentation. I'm open for any other ideas, but thanks already for the ones posted.