Firecast is an auxiliary audio adapter for General Motors factory radios, similar to the GM9-AUX that may be hard-to-find or discontinued. It works by pretending to be a slave cassette player. When powered on, it tells the head unit that it has begun playing, and the head unit will switch to your audio device as its input source.
- You do NOT need to disassemble your radio and splice in a 3.5mm jack.
- You do NOT need to have a slave cassette/CD player (unlike the AAI-GM9).
- You DO need to have the 9-pin connector on the back of your radio, or the cassette/CD player connector that may be hidden somewhere in your car.
In particular, you need access to the three audio wires that go into the head unit, the E&C bus (one signal and one ground wire), and a power source. For the bill of materials, you will need an arduino and a handful of circuit components to connect the arduino and your audio device to those wires in your car. See the schematic for more info.
Firecast was developed on the Monsoon sound system in my Pontiac Firebird. It should work for other radios, but your mileage may vary.