So I just started out with custom KSP controllers and ran into a similar issue regarding the throttle.
I'm using KSP 1.4.1.2089, with Simpit 1.2.4.53 and Arduino library version 1.1.3 . I have turned verbose logging on.
My code regarding the issue boils down to the following:
int16_t val = 32767; // At this point this is just a static value
simpit.send(THROTTLE_MESSAGE, (unsigned char*) &val, 2);
Action groups work just fine (activating, deactivating, toggling). AG actions also lead to according debug output in the KSP console.
Sending the message above however doesn't give any message in the debug console inside KSP. The issue seems to be on the KSP end, as the message seems to be sent successfully (as indicated by a flickering TX LED).
Maybe I'm not seeing it, but an even more verbose output, that would also log failed transmissions and such, would be helpful.
With my setup (that until my order arrives only consists of a 3-state switch), it works just fine: switching between 0, 50 and 100% throttle. With that now I could even launch a small satellite into orbit. All that's missing for complete control (at least in my book) now is switching of SAS modes (prograde, retrograde, hold, ...). If someone knows a mod that lets you assign SAS modes to action groups that would however work just as well (I couldn't find a working solution with some quick googling).
