Nav screen useless by itself?

davipt · #1 09-15-2006, 04:50 AM

Quote:

Originally Posted by Brian-bmw

That is an interesting idea. It would probably work for backup camera, but I am not sure if it would work as a video source. The reason is that this is designed to work in conjunction with a navigation module. It probably emulates a TV module to the nav computer, and then nav computer puts the "Television" option on the main menu that activates it. So, without the nav, there might not be a way to tell it to turn itself on.

Where have you seen that this requires the navigation module?

Please note that both the navi and the tv module are able to generate the menus on the screen, but when both modules exist, the tv overrides the navi:
- with navi: navi R+G+B connect to screen R+G+B
- with TV: tv R+G+B (same pins) connect to screen
- with navi and tv: navi R+G+B aren't used, and an alternative set of pins, plus another pin called "navi sync" connect to the TV's second connector.

Thus the TV generates the menu structure, and whenever the navi has a map to show, it sends a "please let my screen signal pass through" to the tv.

Back to the ebay module, it looks like a simple composite tv (RCA, whatever) to screen resolution adaptor. It would pass the input video signal into the screen, but won't provide any menu like the original.

Brian-bmw · #2 09-15-2006, 07:06 AM

Quote:

Originally Posted by davipt

Where have you seen that this requires the navigation module?

I have not seen this requirement anywhere, but it is somewhat implied by the way the BMW systems work. This is specifically advertised for someone who has a navigation system without a TV module. It would not really be designed for a car that had a screen and neither nav nor TV, and someone who already had a TV module would not buy it.

Yes, it does have the composite to BMW conversion, and I suspect that it emulates a TV module to the nav computer. However, when the TV module and nav computer are connected in tandem, the TV acts as a slave and expects the nav to tell it when to turn on. Therefore, if you have no nave as the primary, I suspect that this video module does nothing, since it probably always assumes that it is the slave.

This is all conjecture, since I have not seen one first hand. But it would be consistent with what I know of the nav and TV module behaviours.

Brian-bmw · #3 09-15-2006, 07:10 AM

Quote:

Originally Posted by davipt

when both modules exist, the tv overrides the navi

This statement is actually opposite. The TV and nav modules are in a master/slave configuration. However, when both are present, it is the navigation that overrides TV. I have both, and I have tried it. The nav runs the screen whenever it is connected. The TV only runs the screen when it is the sole component connected.

Now, the video signals pass through the TV module when both are connected, but it is just a pass through. The actual signals come from the nav computer. And, the TV module just stays idle until told by the nav computer to turn on and steal the signal path.

davipt · #4 09-15-2006, 07:25 AM

Quote:

Originally Posted by Brian-bmw

Now, the video signals pass through the TV module when both are connected, but it is just a pass through. The actual signals come from the nav computer. And, the TV module just stays idle until told by the nav computer to turn on and steal the signal path.

Thanks for clarifying it. As I saw the nav -> tv -> screen, I thought it was the oposite.

Brian-bmw · #5 09-15-2006, 09:38 AM

Quote:

Originally Posted by davipt

Thanks for clarifying it. As I saw the nav -> tv -> screen, I thought it was the oposite.

And I have a further clarification to my clarification

In the MKI system, the TV module was the master over the navigation computer. (The TV module was required, actually.) So, in the MKI, it worked exactly as you described in your note. The one difference is that the MKI nav computer did not have any logic to run the menus on the screen-- the TV module did all of that.