The Smartphone Quick-Jack Solution repurposes the standard 3.5mm stereo audio jack found on most smartphones into a self-powered data channel that makes communication with these smartphones as easy as plugging a headset jack into the audio port. The hardware/software platform is designed for iPhone® and Android® smartphones. This project will make it easy to connect external devices into a phone. It gives smartphones application developers an easy way to add context-aware application features, input user and environment data, or connecting peripherals. And also provides end-product designers instant access to smartphones’ convenience, appealing user interface, and cloud connectivity.
This project is compatible with both Open Mobile Terminal Platform (OMTP) and American Headset Jack (AHJ) standards; the hardware identifies the type of headset automatically and configures the hardware accordingly. First, a comparator circuit detects the type of headset port Quick-Jack has been inserted into. The result is interpreted by the LPC800, which then configures an analog switch accordingly. The analog switch connects the right pin of the jack plug to the right signal on the circuit board (GND/MIC).
For more detail: Smartphone Quick-Jack