Reverse Engineering the Radio

[CrazyWingman]

Hi all. I've just found this forum, and the topics here seem to align with a project I'm working on.

I'm currently trying to reverse engineer the protocol that GM uses to communicate between their head units and cd changers. I have a standard head unit (AM/FM/CD), and it has an expansion plug on the back for a cd changer. This plug includes a Class 2 data pin, so I'm assuming that would be how the two communicate.

Now, I don't really want a CD changer, but I would like to be able to immitate one, so I'm trying to decode GM's protocol. ...and, I'd like to do so without having to buy a CD changer and watch what it does (that will be a last resort).

Does anyone know of anyone else possibly working on this same project? It's proving to be a bit more daunting than I expected, and I'd rather not struggle through ground someone else has already covered.

Thanks.

[kabbott]

TTT Anyone?

[CrazyWingman]

TTT? :huh2:

Google seems to imply that I maybe just got insulted. Anyone care to clarify how badly?

[kabbott]

to the top
just trying to revive your post as i to would like info on
class 2 radio.my ipod would be great with my steering wheel
controls

[CrazyWingman]

Ah - excellent.

Sorry for the confusion. First Google hit was "Thought That Too", which didn't make sense, and next several seemed to imply that it was an insult of various forms.

Alright - enough non-relevant chatter. Hopefully someone will take notice of 3 new posts in this thread and make an interesting comment.

P.S. Have you done any research of your own into this topic? I have a binder full of nearly-relevant stuff here, but it's mostly things like SAE's J1850 and J2178 specs. Neither of those actually say anything about audio controls, other than to specify recommended bus addresses for them. I'd be interested in hearing if you've come across anything better.

[Chris@HPTuners]

Sorry but i don't have any info of the stuff you are looking for. The only time we took a look at the radio is on some trucks the damn thing doesn't stop talking when its supposed to which is a minor annoyance when reflashing.

Good luck,

Chris...

[CrazyWingman]

Hey - thanks for the reply, Chris. Interesting you should mention about the radio never shutting up. I'm actually currently considering removing it from my car so I can hack it on my desk. Then I won't have to listen to the other bus instruments, nor will I have to worry about sending messages to the wrong listener. Haven't decided yet whether I'll just unlock the radio, or attempt to mimic the controller module which responds to the VIN request (which actually seems like it would be pretty easy - I already know what the message looks like). My current problem is that disconnecting the antenna cable looks more difficult than I was hoping (I don't remember it looking like a nice "pull the plug" or "unscrew the bolt&quot- need to crawl back in and look at that.

If I ever find more time to work on this project, I'll be sure to update this board with what I've found.

[Main_One]

I'm interested in retrofitting a steering wheel with the DIC/radio controls into my 03 Avalanche with the Bose radio/CD changer option. I have the steering wheel, and I believe getting the DIC functional is not going to be difficult, but I'm wanting to figure out how to get the radio to respond to the steering wheel buttons. Any help with this would be much appreciated.