Interfacing COMAND to external video (not TV tuner)

[colh]

I've been looking around at the interfaces which allow you to pipe video into a (D2B) COMAND - i.e. they act as a fake TV tuner.
The ones I've seen so far seem to plug in via the C1 and C2 connectors (with just a few wires connected), but there is no piggy-back/daisy-chain - so does this mean you lose your CD changer???
Which then makes me wonder - what about the other signals that will no longer be connected into the car either, such as the CAN-B and D2B wakeup - aren't those important??

Col

[apologies for cross-posting to another MB forum too, but I'm too new around here to know where's the best place to ask.....]

 

[miro]

The TV tuner has its own analog input into the head unit.

One side is RGBS with inverted sync and it has stereo audio input. The other part of the equation is the CAN signal which tells the head unit the item is attached and that it is present.

Even if you were able to provide the correct video signal then you would not be able to present an image. The CAN signal pair must be active.

For what it is worth there are several work arounds. The Dietz and such TV interfaces are awful with image quality but there are some decent image converters around for the picture side.

You can in reality combine both to get a decent result.

Look on German eBay for "Mercedes TV" and you will find several low end solutions for the COMAND 2.0 CD based units.

 

[colh]

Right, I'd seen those signals mentioned on connector pinouts. But that connector also has the CAN-B bus, a D2B wakeup, and CD changer supply pins - so all these are lost if you install, for example, a Dietz interface???
I can only assume that the CAN-B on this connector *only* goes to the CD changer, else other stuff would stop working too. But I would have thought perhaps that the CAN-B is for COMAND to talk to the instrument cluster? Maybe not (I must check tonight on the WIS wiring diagrams, I think!).

Interesting views on the Dietz - I guess its the quality of their composite-RGB conversion that's the problem, or else just plain supply noise.
Don't suppose you know what is needed on the CAN side of things? - does the COMAND need to actually communicate (intelligently) with the tuner/interface, or does it just need to not have its CAN messages time out (I must admit, CAN is one of the few serial interfaces I'm not familiar with - yet!)

 

[Alfie]

Right, I'd seen those signals mentioned on connector pinouts. But that connector also has the CAN-B bus, a D2B wakeup, and CD changer supply pins - so all these are lost if you install, for example, a Dietz interface???
I can only assume that the CAN-B on this connector *only* goes to the CD changer, else other stuff would stop working too. But I would have thought perhaps that the CAN-B is for COMAND to talk to the instrument cluster? Maybe not (I must check tonight on the WIS wiring diagrams, I think!).

Interesting views on the Dietz - I guess its the quality of their composite-RGB conversion that's the problem, or else just plain supply noise.
Don't suppose you know what is needed on the CAN side of things? - does the COMAND need to actually communicate (intelligently) with the tuner/interface, or does it just need to not have its CAN messages time out (I must admit, CAN is one of the few serial interfaces I'm not familiar with - yet!)

The TV inputs use different pins on the C1/C2 to the CANBUS and D2B wakeup. You wont lose those.

 

[miro]

TV CAN is not the same as CAN for the rest of the car. It has nothing to do with wakeup unless you are talking about DVD based cars.

 

[colh]

Yep, I'm with you (both) on all that. Thing is, the interfaces I've seen seem to have their own C2 connector! (which they of course need for their own TV-CAN connections) No sign of it piggy-backing into the original C2 which does have the CAN-B connections.
AND it pinches the C1 connector, which I believe normally routes through to the cd changer...
Unless I'm missing summat - see what you think:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=018&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=280068111769&rd=1&rd=1
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=005&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=150081301695&rd=1&rd=1
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=013&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=230074545825&rd=1&rd=1

 

[miro]

You merge the pins from both connector sets onto one setup. The leftovers you put aside.

It probably does steal power from the CD changer but then all you need to do is design a solution that meets your needs.