My goal is to build an extremely low cost quadcopter, by using the sensors of my smartphone (it will be mounted on the quadcopter). The arduino will only control the speed of each motor, as received from the smartphone. What methods exist to transfer data from a smartphone to arduino?
My first idea was to simply use USB, but it turns out that my smartphone doesn't support the USB host mode. Is it possible to send data over USB without USB host mode? What alternatives do I have? I thought of using the audio port: Can I directly connect an audio channel to analog in?