Patent ID: 8683090

Claim:
A host device comprising: a connector including: a power contact operable to receive a voltage from an accessory, the power contact forming part of a power path between the host device and the accessory; and a data contact operable to exchange data with the accessory; and control circuitry coupled to the connector and operable to: measure a first voltage received from the accessory via the power contact; send an instruction to the accessory via the data contact, the instruction instructing the accessory to alter an impedance, at the accessory, of the power path between the host device and the accessory; sink current from the accessory via the power contact; measure a second voltage received from the accessory via the power contact after sending the instruction instructing the accessory to alter the impedance of the power path and after sinking current from the accessory; determine whether the accessory includes particular circuitry based on whether the first voltage is different than the second voltage; and charge the host device using power received at the power contact when it is determined that the accessory includes the particular circuitry.