Method and apparatus for operating accessory interface functions over a single signal

A method of interfacing an accessory to a radio, comprising:

• coupling the accessory to the radio via a plurality of interface contacts;
• detecting the accessory at a single contact via a first comparator of the radio;
• reading a memory device, located in the accessory, at the single contact at the radio;
• and
• detecting accessory PTT presses at the single contact via a second comparator of the radio.

An interface system for an accessory and a radio, comprising:

• an accessory interface, comprising:
• a memory device containing accessory configuration data, the memory device having a first pull-down resistor coupled thereto;
• a push-to-talk (PTT) switch having a second pull-down resistor coupled thereto;
• a radio interface, comprising:
• a first comparator having a pull-up resistor coupled to an input terminal;
• a second comparator having an input terminal coupled to the pull-up resistor;
• and
• the memory device, PTT switch, first pull-down resistor, second pull-down resistor, first comparator, and second comparator are operatively coupled via a single signal line, wherein:
• the first comparator detects that the accessory is detached from the radio via the pull-up resistor,
• the first comparator detects that the remote accessory is attached to the radio via a first voltage divider formed of the pull-up resistor and first pull-down resistor,
• the accessory configuration data is read from the memory device in response to the remote accessory being detected, and
• the second comparator detects PTT presses via a second voltage divider formed of the pull-up resistor and the first and second pull-down resistors.

An interface system for an accessory and a radio, the interface comprising:

• a controller at the radio;
• a memory device at the accessory having accessory configuration data stored therein;
• a first comparator at the radio for detecting accessory attachment and detachment, the controller reading the accessory memory device configuration data in response to an accessory being detected;
• and
• a second comparator at the radio for detecting accessory PTT presses, the accessory PTT presses being detectable by the second comparator only after the first comparator has detected accessory attachment and the controller has read the accessory configuration data.