However, their support isn't bad and they sent me the protocol specification within one day of me asking. Here is the Growatt Serial Comms Protocol as PDF. The comms protocol is a tad odd, and the spec isn't 100% clear in all situations but with a bit of fiddling I got a perl reader to work. The comms implementation isn't very robust; while experimenting I managed to send it into a catatonic state a few times, and it stuffs up the message checksum that it sends every now and then, too.
Without further ado, here's my perl proggie. It doesn't work with the growatt's super-weird dynamic address mode (shows as "MOVE" on the LCD); knock through the menus and set a fixed address value first. The perl proggie also expects a unixy box with /bin/stty because I couldn't be bothered to do the tedious termios fiddling from within perl.
