Successive approximation resistor detection

摘要

An apparatus comprises a connector configured to receive an electrical contact of an accessory device that is electrically coupled to a resistor of the accessory device, a current source configured to apply a specified current to the resistor to generate a resulting voltage, a comparator configured to receive and compare the resulting voltage to a reference voltage, and a controller configured to store an outcome of the comparison as a bit in a register, to adjust the applied current using the outcome of the comparison, and to determine a resistance value for the resistor using the bit stored in the register.

主权项

1. An apparatus, comprising:
a current source configured to apply a specified value of current to a resistor of an accessory device to generate a resulting resistor voltage when an electrical connection to the accessory device is detected; a comparator configured to receive and compare the resulting resistor voltage to a reference voltage; and a controller configured to: repetitively set the value of current applied by the current source to the resistor of the accessory device according to bits stored in a register, initiate comparisons of resistor voltages resulting from the applied current to the reference voltage, update the bits of the register according to outcomes of the comparisons, and change the value of the current applied by the current source according to the updated bits of the register; and identify a function performable by the accessory device using the bits stored in the register.