JVC j-link protocol

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Until recently I had a JVC head unit and CD multi disc changer installed in my car but following a heavy rain storm, the boot (trunk!) leaked and the changer has suffered some water damage. The HU works fine (I'm not discussing audio quality here - it is adequate for my needs!), but I thought it would be nice if I could hook up an MP3/ipod/etc to the CD input. The problem is that the HU needs to see a working changer before allowing the switch over. The HU is a circa 1998 KS-RT710 with an mini 8pin DIN connector but the CD changer end is similar to the Sony unilink connector. Later JVC HU's seem to use the same connector at each end - there are AUX-in cables on ebay which seem to work on the later units but not the earlier (mine!) HU's. Does anyone have any information on the signalling protocol so that a PIC could mimic the changer?.

Many thanks
Dave

PS been lurking for a while, I ought to post in the introductions soon!.
 
I'm not aware of anyone who has the J-Link protocol defined, as it's much like the Alpine Ai-Net and is proprietary.

To be honest with you it might be less time and effort to get a cheap semi-functional CD changer or other module off of eBay or something similiar and use the analog channels with a custom RCA jack pair.

That's how it's done in some late model vehicles with similiar CD changer controls...the factory analog wires are "switched over" to an alternate input for the iPod, XM Radio, etc....the head unit sees a working/playing changer, and doesn't care about the analog source itself.

Well, just some ideas to toss up. :)
 
Someone by the name of cleggy seemed to have some information on the link but the webpage has gone. There's been a couple of attempts to decode the protocol on mictronics.de but no further info. The Kenwood is much easier - just 1 resistor signals Aux in!.

I browse ebay occasionally for a suitable CD changer - something will turn up but I can't justify buying another head unit - or rather I can't justify to my wife!.

Dave
 
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