A cheaper and dirtier way to do this is to solder onto controller's pcb. Each joystick drives an X and a Y variable resistor, and measuring the voltage across o

A cheaper and dirtier way to do this is to solder onto controller's pcb. Each joystick drives an X and a Y variable resistor, and measuring the voltage across output and gnd pins shows it ranges from 0 to 3.3V with 1.67V at neutral position. After removing these resistors from the board, you attach the pins to the arduino and you can analogwrite an output voltage[1] to mimic the joystick movements. This of course flows through to the radio transmitter and onto the drone giving you computer control of the drone without reverse engineering radio and packets. I'll be writing a blog post on this soon. [Though I would be curious if anyone has done this with a Syma (D63) as it's a chinese company] [1]: also need a low band pass filter (couple resistors and capacitor to trun the arduino's pwm into true analog voltage)