Feiyu Mini 3D still lives

Feiyu Mini 3D alternative firmware (2 min 4 sec)

Still managed to not burn out the motors or break the flex wires. These are considered the mane risks for any development on it.

Stepped the IMU & feedback up to 2khz, but the mane limitation is nothing else can happen while I2C is being accessed. The IMU board has to send the readout & wait for a data packet to make a full round trip to all 3 microcontrollers & back before taking the next reading. Function indirections contributed quite a delay to the I2C driver so inlined a lot of it.

Much PID tweeking got useful pointing accuracy but not as good as stock, despite much higher current. The reluctance cogging ended up not a factor. In certain parts of the rotation, it slightly vibrates when fighting reluctance cogging, but it doesn't ruin the video. The feedback allows it to do smooth panning with no evidence of the cogging troubles.

Decided to implement the full auto centering using the hall effect sensors. So if it's within 10 deg of the target position, it uses the IMU. If it's outside 10 deg, it uses the hall effect sensors. There's a small jump when transitioning because the hall effect sensors aren't as accurate as the IMU, but it's better than a complete loss of control when it bumps into something.

Mixing of the roll/heading motors is definitely horrid. It didn't work in the stock firmware, but it was better. There's never going to be variable pitch or ability to initialize upside down. These problems are solved with matrixes & needing a matrix to solve kinematic problems has always been a career ending event.