All versions of the firmware work great, except GP. [Marina has] mixed feelings about this since it's 10 years old now and these devices aren't circulating much. The loop type can't be changed (and register 85 doesn't exist yet) so that messes get_pid(), though set_pid() can be used if the loop isn't specified. The totalizer command is missing the dollar signs ({addr}T\r instead of {addr}$$T\r so it doesn't like this. Only GP actually uses the dollar signs, though everything else is backwards compatible. And lastly, the {addr}VE command also wasn't around yet, so GP isn't recognized to stop it from continue to create_mix() function. {addr}??m8 would work, but only for GP which is annoying.

Originally posted by @marinapalese in #15 (comment)