Here's a modification of original ArduPilot, running on Arduino Pro Mini.I'm just posting photos for now, since there's still lots of things to do for my planes to fly. Maybe when things are tuned, I'll post also modified code.My first testing or original ArduPilot few weeks ago was disaster, I tried to see my plane to see directly follow path, so I skipped slow testing of everything in small steps. Result was plane out of control, flying away to distance. Later I found it using bike, 1.5 km away. I had luck that time, I could have some $350 flown away, or maybe breaking someone's roof. Anyway, my previous plane was not flying nice, so this one is replacement, and it flies good in manual mode.
See the Arduino Pro Mini, compared to ArduPilot. It's smaller, and it lacks mux and failsafe chips. So great care must be done for switching between autopilot/manual modes on main cpu. Luckily tests show that it can be done relatively nicely using interrupts, so if main program control locks, interrupts still keep running, providing the possibility to gain control over plane.
Arduino Pro Mini on left, ArduPilot board on right.So far I play with FMA copilot replacement, implementing just stabilization. 6 RC channels are read, and 4 are written, the code can pass 4 channels through unmodified, or read them and mix with other values.