How do I interface with a drone?

Question

I recently bought a drone(quadcopter). I like how the drone works but now I would like to create an application that will allow me to control the drone remotely from my PC or Phone.

How does a computer or phone interface to an aerial vehicle?

Some of my initial thoughts were

1. Get a RF detector and detect what signals are being sent to the drone and replicate it using a new transmitter.
2. Replace the control circuit in the drone with an Arduino and send corresponding signals to it to fly the drone

Both these methods seem to be kind of far fetched and hard, but I'm not sure how this could otherwise be done.

Answer 1

With a conventional RC vehicle, I would probably suggest getting your own receiver-transmitter set (something like XBEE transceivers or similar) and completely gutting the original system, but with a small quadcopter like you have, I think trying to replace the receiver would be very difficult to do while maintaining the aerodynamics of the vehicle.

You could try to monitor the control signals and re-create them, but a third option you might consider would be to spoof the input devices on the transmitter. That is, as I see it, you could:

1. Replace the transmitter-receiver pair (not recommended due to receiver form factor).
2. Spoof the transmitter output (requires purchasing another transmitter-receiver pair of the same frequency with which to line monitor and spoof).
3. Spoof the transmitter input.

The last option is what I would recommend. Get a multimeter and check the joystick outputs. I would imagine they're just potentiometers; I would expect a battery V+, a battery ground, and an analog voltage output. Then all you would need to do is to duplicate that functionality. Best case scenario would be that analog voltage falls within the same band as an Arduino analog output, in which case you could just wire ground to Arduino ground and the analog output direct to the joystick analog output line (after you remove the joystick).

Failing that, you could buy digital potentiometers and duplicate the functionality. Depending on how clever you wanted to be (and how much space is available) you could install a USB port and a switch to jump between joystick and Arduino control and have a modified computer-capable transmitter that can also be controller by people.