When I started driving, I wanted Bluetooth in my 2004 Jeep Grand Cherokee. Several years later, I finally got around to building a Bluetooth mod. My radio has a plug for a cd changer, so I used an Arduino and a Bluetooth module to make a pseudo cd changer. It took me about a month, however I procrastinated a lot. Here's a video of the prototype working (ignore the awful music).

• The arduino prototype code is in Jeep/ and the ATtiny version's code is in src/
• My radio model is p05064354aj.
• I'm using an Arduino UNO and a XS-3868 Bluetooth module
• Chrysler radios, made before 2004, use the car’s internal PCI bus for communication with other accessories (i.e. a cd changer). It’s a good idea to be careful when writing to this bus because you could damage your car.
• My car uses the J1850 VPW protocol.
• Some good vocabulary to know for this protocol:
  • Frame : a packet of data
  • Cyclical Redundancy Check (CRC) : it’s a checksum
• I used two optocouplers to communicate on the bus without frying my Arduino. Also, I put some LEDs on the optocouplers' outputs which was useful for debugging.

• This has a lot of information on what to send to the radio to trick it into thinking you’re a cd changer.
• This has good info on the J1850 protocol.
• A more technical document on J1850.
• This guy’s project uses the same protocol so it was helpful.
• Radio Pinout (there are also other radio pinouts here)

• Finish converting from the Arduino prototype to the ATtiny version
  • CRC check (Frame Creation in general)
  • Proper Responses to the radio
• In the current configuration, the relay is unreliable so that needs to be fixed

Benjamin Thomas - [email protected] - 2019