You have 3 options:
- USB: you’ll need an USB OTG cable and make sure that your Android device supports USB OTG.
- Bluetooth: you’ll need a bluetooth module. AutoArduino was tested on a HC-05 module so that one works for sure at least.
- Ethernet: you’ll need an Ethernet shield for your Arduino. AutoArduino was tested on the Shield Ethernet W5100 module so that one works for sure at least.