When tuning PID parameters for the HCD flight controller I pretty much spend 2 evenings waiting for the program to recompile.
I would change some parameter a tiny bit, recompile, get the HCD in the air to evaluate and then repeat the process over and over.
At some point I realized that tuning the parameters in mid-air would be much more efficient.
For this i made this simple controller:
It’s simply 6 faders hooked up to an Arduino. It transmits the 6 fader values to the flight controller software where they are scaled to the appropriate range and fed into the feedback controller in real time.