A system and method for data transmission and power supply capability over an audio jack for mobile devices are disclosed. A particular embodiment includes: a peripheral device including an energy storage component, a microphone using a microphone bias voltage, and a select switch configured to provide a first switch position wherein charging of the energy storage component using the microphone bias voltage via the microphone conductor is enabled, the select switch being configured provide a second switch position wherein charging of the energy storage component using the microphone bias voltage via the microphone conductor is disabled; and a mobile device and an application (app) executable in the mobile device to produce a switching tone on the audio signal conductor of the audio jack, the switching tone causing the select switch to transition to the first switch position or the second switch position.