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I'm in the initial research stage of a project to get a general purpose computer (CarPC) running through the PCM. The end goal would be to have a stand-alone Linux-based MiniITX PC for MP3 playback, video, and Internet access with some custom electronics for receiving input from the standard PCM controls and seamlessly injecting audio and video into the PCM (probably with a switch to go between standard PCM functionality and the 'CarPC').

The project will take some reverse engineering, so the first step was to get as much of a working PCM environment as possible running on a workbench.

1) Does anyone have any clues as to what's the minimum amount of eqipment required to get the PCM to even start up? Instrument cluster? Amplifier? Full MOST setup?

2) Any suggestions on where to start looking for parts? I have a 'full' PDF catalog of 997 parts, but I haven't been able to find an online store that has anything I would actually need. Would it be advisable to simply order the parts from my local Porsche dealer?

3) Has anyone tried to do anything like this before? It seems the MOST-Bus tends to scare away most of the hobbyist community.

Anyway, thanks for any pointers or hints in advance!

-Brian

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:eek: This is going to be quite a project, I think if you are self financing it, things may get expensive.

To bear in mind, the PCM units are unlocked by reading the code from the instrument cluster. This is done over the CAN bus. When you start getting to protocol level, although you can find a fair ammount of information of the hardware implementation of CAN, the communication protocols are propriety. I can't imagine Porsche, Becker or Harman will provide any technical reference literature to the protocols - even at a high cost. This will apply to the MOST bus too.

Setting up you workbench, you will have to buy the connector shells from Porsche, but you can't buy the pins individually. If available, they come as a repair pack, where there is a pin already crimped to each end of a yellow wire.

You would probably be better off spending your cash on getting a touchscreen VGA integrated so it looks factory and just run stuff on the car PC.

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:eek: This is going to be quite a project, I think if you are self financing it, things may get expensive.

To bear in mind, the PCM units are unlocked by reading the code from the instrument cluster. This is done over the CAN bus. When you start getting to protocol level, although you can find a fair ammount of information of the hardware implementation of CAN, the communication protocols are propriety. I can't imagine Porsche, Becker or Harman will provide any technical reference literature to the protocols - even at a high cost. This will apply to the MOST bus too.

Setting up you workbench, you will have to buy the connector shells from Porsche, but you can't buy the pins individually. If available, they come as a repair pack, where there is a pin already crimped to each end of a yellow wire.

You would probably be better off spending your cash on getting a touchscreen VGA integrated so it looks factory and just run stuff on the car PC.

Yeah, I expect it to be an expensive project -- somewhere in the range of $10k-$20k. I know the safest solution would be to start 'from scratch', but I really want to try to keep the OEM Navigation functionality intact. I think that may mean a 'man in the middle' approach, building a circuit to go between the the output module and the LCD display and the same for audio and input. And I can probably get started with this even if the PCM is not 'unlocked'... assuming all the internal components are active (something shows up on the screen at least (?)).

Does anyone know if repair manuals or circuit diagrams of any sort exist for the PCM? I know Becker manufactures these things, but I haven't found any other information. Porsche circuit diagrams just show the very high level input/output of the units.

-Brian

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  • 2 months later...

Just a suggestion.. The Cayenne PCM includes an AV interface button. This would allow a simpler connection to other AV devices such as a car computer MP3 or DVD etc. www.nav-tv in the USA offer interfaces for the cayenne pcm 2.1, or you could try AudiotechnicDietz.de who also offer similar. The standard PCM2.1 in the 987/997 doesn't have the A/V interface , this may be a lot more difficult to retro fit.

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I was in the middle of building in my own video integration and I found out that TVandNav2Go already has a video solution for the 997. I'm just about to pop my PCM screen out and send it to them for modification (it involves unit disassembly and soldering). I'll post results.

-Brian

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  • 2 weeks later...

I got the PCM back.

The video input is composite-only, and displays too much temporal aliasing (pixel crawl) to be usable for a computer display. The system is good for what it's primarily intended for, though, which is watching DVDs.

-Brian

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