[Joe] was experimenting with his Arduino when he started thinking about how he could get it to communicate wirelessly with his Android phone. Bluetooth is an option, but it requires some extra components, and Google’s ADK works as well – just not wirelessly.
Instead, he thought it would be neat to see if he could get the two devices to communicate with a simple magnetic coil. He constructed a small 1cm diameter coil, connecting it to the Arduino via a resistor and diode. Using the Android Tricorder app, he was able to locate his phone’s magnetometer, after which he ran some tests to narrow down the best sample rate and frequency range for communications.
To transfer data between the two devices, he had to bit bang the signal in software, since the Arduino’s UART has a lower limit far faster than the 7 bps data rate he was able to achieve with the magnetometer.
While his wireless Arduino to Android bridge isn’t likely to win any awards for throughput, it is a great proof of concept project. Be sure to check out the video below to see his “poor man’s NFC” in action.