Patent ID: 8958573
Filing Date: 2015-02-17
Classification: H04M

Abstract:
1. A system for controlling an electronic device, the system comprising: an accessory coupled to the electronic device, the accessory having a user control interface for receiving at least one input, and a tone generator; the accessory configured to, in response to an input, generate a corresponding control tone using the tone generator, and send the control tone and a calibration sequence to the electronic device; the electronic device operable to receive the calibration sequence and control tone, and including a zero-crossing detector operable to determine at least one of the start or ending of each of the calibration sequence and the control tone and having a circuit operable to determine the periods of the calibration sequence and the control tone based on the zero-crossing detector output; the electronic device further operable to compensate for errors in the control tone based on the periods of the calibration sequence and the control tone to determine the input, and then execute an action based on the input; the system configured for biasing the accessory with a bias voltage and detecting the presence of the accessory by detecting a period value after powering on the accessory.