Introduction: How to Let the Phone With Android to Control Servos Via Audio Channel

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If in program on Android phone it's hard to get access to serial port or, as it was in my case - I couldn't find a connector for my phone, it's possible to let the Android phone generate necessary logical signal via audio channel. To test it I made the phone to control two servos (via stereo output channel).
Because I did not want to damage my phone during development I connected to it first via bluetooth headset. When schema was completed and tested I successfully tried it directly via audio jack.