TV on Nav Plus whilst moving

[Jeeves]

The question must have been asked before, but I can't find the answer and would be grateful if anyone can enlighten me.

Now the kids know there's a TV, they want to see the screen (and not just hear it) on my Nav Plus.

Found a site www.tectronics.com/tectronics which offers a 50 Euro box of tricks, but payment is in advance and they don't show any way of connecting it (except pictures of a more expensive device for BMWs).

Anyone know anything?

[Dippy]

Assuming you don't have the DVD version (which has this feature controlled by CAN and therefore is not simple to turn off), then you just need to remove the GALA signal from pin 1 (IIRC) of the main ISO connector. Since this GALA signal also controls the volume-increase-with-speed feature, it is common to use a switch so that this can be restored for CD and radio.

[Jeeves]

Thanks Dippy.

But Martyn C has quite rightly reminded me that mine's DVD based. That probably rules out the Tectronix box then.

[simple1]

erm, forgive me if i am wrong here, but CAN is part of the system that lets all the ECU's talk to each other, therefore in the DVD based systems, the volume and screen control are triggered by one of several ecus and not by the yellow/pink wire

[peterb]

erm, forgive me if i am wrong here, but CAN is part of the system that lets all the ECU's talk to each other, therefore in the DVD based systems, the volume and screen control are triggered by one of several ecus...

Indeed, but disconnect the CANBUS and you lose ignition on/off signals, lighting signals etc. Also, the HU will power down after a little while of not receiving signals on the CANBUS.

A guy on Tyresmoke has built a little circuit to establish CANBUS communication momentarily every little while - this keeps the system running but disables the screen blanking.

[Dippy]

Thanks Dippy.

But Martyn C has quite rightly reminded me that mine's DVD based. That probably rules out the Tectronix box then.

Not necessarily. As has been pointed out, the Nav unit learns that the car is moving by signals on the CAN bus. It would be possible to put a CAN-enabled device in line with the unit which would filter out these signals. It wouldn't necessarily have to be that expensive either.

I suggest you ask the company in question. By putting some English on their website it suggests that they welcome English-speaking customers...

[JohnW]

building a can bus device is a piece of p!ss, the hardware to do it costs at most a couple of quid.

The best way is to try to get the correct connectors so the loom doesn't need to be butchered and plug it in-line.
After that it is simply a case of scanninng the bus to determine what messages are flying about, and filter out the ones you are concerned with, possibly spoofing false acknowledgments.

If I had the time I'd build one, but I haven't unfortunately. I will see if I can plug a CANalyser in at some point and log the activity though. Can anyone tell me the pins to monitor and the easiest place to get at them ?

Cheers,
John. (lots of knowledge of CAN )

[Dippy]

Surely on the car in question the diagnostics port is CAN based?

On an older car I think the easiest way to get at the CAN is at the Sat Nav head.

[JohnW]

It may well be dippy, but I don't think it is. I am pretty sure the diagnostics port is not CAN based as it uses a standard serial (rs232) interface. The only special thing about the lead is the connector.

CAN is a differential signal (similar to RS422, RS485, or I2C) and needs a specific node termination in order to connect to the bus. This is normally done with a 'CAN interface' chip. The cheapest way to get one of these is to buy a Microchip PIC microcontroller with a CAN interface on board.

The diagnostics port generally don't plug striaght onto the bus to ensure that if the car bus is shorted/open circuit at least diagnostics can be used to report the loss of connection.

I think your right though, satnav head or clock display is possibly the easiest access point.

[Jeeves]

I suggest you ask the company in question. By putting some English on their website it suggests that they welcome English-speaking customers...

Question asked in English, but so far no response. Wieder, aber jetzt in Deutsch denke ich. Will keep you posted.

(Did see another thread re older Nav system on A2 etc, it's on p3 or 4 of RS6 forum for anyone interested.)

[Dippy]

Erwähnen Sie nicht den Krieg...

[Jeeves]

Don't mention ze war......

[Jeeves]

You may have already found this anyway, but apparently there's a Dietz 1280 unit which does the trick and can be found for < 199 Euro on Ebay. Someone in the US offers a plug and play version of the same, but doesn't take international orders. Anyone know anymore?