Using an OEM vehicle navigation screen

**rando** · 05-26-2004, 03:08 PM

Originally Posted by Mr Castulucci

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.

Something solid state. Truthfully though, I'd worry mostly about getting a proper VGA signal to your screen first. One you make that work, you can worry about switching. If you can convert your screens input to VGA, perhaps you can convert your NAV units output to VGA as well. In that case, a standard VGA switch box would do the trick.

**Mr Castulucci** · 05-26-2004, 07:56 PM

Needs,

Thanks for sharing your experience. I'll certainly be looking out for the doubling up that you described.

However, I think that I may be able to convert the image anyway. I've done a lot of work with creating a VGA controller from scratch via VHDL, so maybe I can swing it. I'm expecting the parts tomorrow, so hopefully I can begin then

Rando, you're right. I'm not going to worry about switching too much yet. Sync conversion first, then switching

Originally Posted by Needstorage

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.

**Mr Castulucci** · 05-27-2004, 02:10 AM

Needs,

I measured the CSync signal coming out of the navigation ECU, and it turns out that you're right about it being at a different frequency than 640 X 480 VGA. On 640 X 480 VGA, a SYNC pulse would occur once every 0.000032 seconds (every 32 microseconds) - in other words, it has a frequency of 31.25 KHz.

The frequency coming out of the ECU is 15.66 KHz (as measured by my equipment). For argument's sake, let's round this to 15.625 KHz (exactly half that of standard VGA). This means that a SYNC pulse occurs once every 0.000064 seconds (every 64 microseconds).

So, if the screen can't adapt to use the "new" sync frequency, I will have to implement some sort of TTL solution. I haven't given it enough thought yet, but maybe I can implement some sort of T flip-flop (which would basically send a sync pulse every other VGA pulse) - although I am pretty sure that this would not work. An alternative solution I have been thinking about is maybe using Windows CE or something to possibly lower the screen resolution to 320 X 240, which I am pretty sure would have the required sync rate. If not, lowering the refresh rate to 30 Hz should do it too, but I don't think that this would be allowable by Windows.

In any case, time will tell. Suggestions?

**Needstorage** · 05-27-2004, 02:34 AM

Originally Posted by Mr Castulucci

So, if the screen can't adapt to use the "new" sync frequency, I will have to implement some sort of TTL solution.

Thought 'bout this too. a T-flipflop indeed... the basic building block of a binary counter

Digital electronics are not a big problem to me, but converting this analog Sync signal to ttl-like signal, and vice versa is something I would not know how to begin with.

Originally Posted by Mr Castulucci

I have been thinking about is maybe using Windows CE

And lose all the power of XP? I'm working with XPe, but as I said, my 7" TS TFT is ordered at carTFT, I give up the idea of using the OEM screen.

Originally Posted by Mr Castulucci

lowering the refresh rate to 30 Hz should do it too, but I don't think that this would be allowable by Windows.

I mentioned earlier, there is a tool to change all kinds of setting of your VGA-card. It goes pretty far (you can mess up your desktop pretty damn good) but don't remember the exact name

However, I didn't manage to get a compatible output signal to feed into the OEM screen.

I will certainly check this thread often to see what you come up with.

**Mr Castulucci** · 05-31-2004, 03:04 AM

Hey Guys,

I'm retarded. I ordered a few of the wrong parts, so I am stuck waiting until Tuesday. I'll keep ya posted when I begin work

**Mr Castulucci** · 06-05-2004, 03:10 AM

Related Posts:

http://www.mp3car.com/vbulletin/lcd-display/27277-hsync-and-vsync-csync-conversion-post213755.html (most current as of now)
OEM Navigation Connectors

Check those out if you are interested in my progress.

**Needstorage** · 07-17-2004, 07:06 AM

Hey, Mr Castulucci... been a while.

I found something very intresting:This is exactly the convertor that we need. (Well for my car I'm 100% sure, but for your car, I assume it wil work too, because we had the same **** happening with our OEM screens.)

Here's the link: Its Interface 1212 that does the conversion

Edit: BTW, you can buy it here

**jmaleixo** · 07-17-2004, 08:17 PM

I have bought it a few months ago ..... and it works fine ... with video camera etc..

But when work with a tv-out of a Via board, the image its not so good

By the way .... we have the same car ....

**Needstorage** · 07-18-2004, 07:05 AM

Wel, maybe you can answer the next question then: When you're driving the car, the in dash OEM screen just switches back to whatever it was in before it was playing the video-signal. (For safety-reasons) Is there a way around this problem?

**Aksor** · 07-19-2004, 08:54 AM

Hey guys check out some of the SONY PS1 LCD to VGA mods.

The Sony 5" LCD has the same RGBS interface and runs on 15kHz.
you can use an ATI or Matrox Video card and power strip an select Arcade mode from the custom resolution this will give you the 15kHz required.

BTW flip flops will not work cause the RGB color data is still sent out at 31kHz and your vertical sync will be out of sync

Laz