Using an OEM vehicle navigation screen

**Mr Castulucci** · 05-13-2004, 03:45 PM

Success (?!)

I called United Radio and they *do* in fact have the service manual. I ordered one and will be receiving it in a few days. I will post again as soon as I receive it.

Oh, and it was $20 (including shipping).

-Frank Lesniak

**god_of_cpu** · 05-13-2004, 03:45 PM

Have you checked out AVElectronics yet? They make a product thats made just for converting NAV screens to video inputs. Its expensive though, like $400 and I don't think it does VGA.

**Mr Castulucci** · 05-13-2004, 03:53 PM

No, I haven't seen that site. I saved the link though and I will definitely contact them depending on what this service manual says....

Thanks for the link!

**Mr Castulucci** · 05-19-2004, 01:31 AM

Hey Everyone,

I received the repair manual and I am surprised at how comprehensive it is! I am going to scan it as soon as I can. I'll keep you guys posted.

Also (thanks to the help of Rando), I am going to take out the navigation head unit in the morning/early afternoon and take TONS of pics (mostly because I don't want to take it apart again until I am actually ready to implement my design). I will post a link to them.

At this point (after looking through the schematics), I believe I can accomplish the following:
-Integrating an alternative VGA source (i.e. CarPC) with the OEM navigation screen
-Integrating composite/RCA (NTSC) video input
-Disabling the fact that you can't change your route while the car is moving

I am also hoping that I *may* be able to use the touch interface with a CarPC. I haven't really looked into this aspect of the schematics yet, but I feel that this will be the most complex part of my project. I'll definitely be reaching out for help to you guys for this part (once I scan the schematics)!

-Frank

**rando** · 05-19-2004, 02:01 AM

Hard cord mod'n of your OEM unit. That's brave dude! I guess worst case, $1600 to OEMVALUE.COM will get you a new OEM unit if you phux0r it up real good.

Good luck!

**Mr Castulucci** · 05-19-2004, 02:11 AM

Haha, yeah. I really wish I had access to a good oscilloscope... It would make it hella easier to do all of this. I'm keeping my eyes open for one of those for sure.

I plan to basically make a switch-based pass-thru connection. It shouldn't be too bad. These spec sheets are really comprehensive. I'll just have to do my homework

Wish me luck!

**Mr Castulucci** · 05-26-2004, 02:02 AM

Brief Update:

I've decided to tap into the Navi System (for VGA, anyway) at the rear of the SUV (i.e. at the navigation's computer). If I had access to a damn scanner, I would post up my block diagram...

But, basically what I am doing is I am going to cut the RGB & Sync lines that go between the OEM navigation CPU & the OEM navi screen. I'm going to connect these lines to a 12V relay (w/ the "default" of the relay set to the navigation). Then, the other input to the relay will be connected to a sync converter which has the function of converting the CarPC's HSync & VSync signals into the CSync (Combined Sync) signal that the OEM equipment uses. This is accomplished by a logical XNOR operation. The CarPC's VGA out is connected to the sync connector.

Hopefully this all works out. Parts are on the way, so I will begin testing ASAP.

I've also put an OPUS power supply on-order, but I don't expect that until mid-June or so.

**rando** · 05-26-2004, 09:19 AM

Hmmm...video signals running unshielded through a relay (i.e. right next to a charged coil) ... are you concerned about introducing noise on your video signal?

**Mr Castulucci** · 05-26-2004, 01:23 PM

Well yes and no...

Basically this will just be my test run anyway, not my final design or anything.

But, one "redeeming" factor is that the coil will be in steady-state, rather than flipping back and forth, which should minimize some interference.

Other than that, I'm going to just try it and see. Do you have any other suggestions for switching? The only other thing I can think of is using some sort of MUX with logical inputs.

**Needstorage** · 05-26-2004, 01:51 PM

Originally Posted by Mr Castulucci

I've decided to tap into the Navi System...
I am going to cut the RGB & Sync lines that go between the OEM navigation CPU & the OEM navi screen....to a sync converter which has the function of converting the CarPC's HSync & VSync signals into the CSync (Combined Sync) signal that the OEM equipment uses. This is accomplished by a logical XNOR operation.

Mr. Castu,

A couple of months ago I tried the exact approach as you describe above. (Look Here, Sync combining) I have a Ford galaxy with a built in GPS-system and a nice screen

I tried to hook up the VGA-output of a standard PC to the connections described in the above link of the back of the unit. I managed to get some output on the OEM screen, but I saw my desktop twice, right next to eachother. The problem you have is that these OEM monitors use a fixed refresh rate and probably a rate that isn't supported by your VGA-output. Like my experience, my V-sync output rate was like double the required rate for the OEM screen. There was no way to put my VGA-card into a mode that enabled this refresh rate. I even tried a tool to set resolutions/refresh rates yourself... i don't remember the name for now.
I do now that the above schematic work, because it combines the sync's indeed, but it does not alter the rate of the signal.