VGA - LEDS - pulldown???

Brian Riley

I have been hard busy here proving out the PRC Rev 2 and PRC-IO board. The processor board is OK. The PRC-IO daughter board composite tv video and PS2 connectors are all OK, but I cannot seem to get the VGA connection working. I used the circuit from the demo board and I have the pinouts and resistors all correct , but no joy. I was wondering ... I just used the resistors and did not include the LEDS and their resistors ... are they being used as some kind of a pulldown?

I did a search of the Propeller forums against "VGA" and I didn't see any discussion of that aspect.

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cheers ... brian riley, n1bq, underhill center, vermont
See the K107 Serial LCD Controller at
www.wulfden.org/k107/

Mike Cook

Brian,

Paul Baker posted this schematic for the P8X32A-Q44 ProtoBoard that Parallax will sell soon. Might help debug your I/O board

http://forums.parallax.com/attachment.php?attachmentid=44624

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Mike

Brian Riley

OK, thanks, that is a start ... now it gets more strange!

The above referenced schematic is identical to my setup (meaning just the resistors DACs, no LEDs) with one exception he has Pin 9 of the VGA 15 pin connector attached to +5vdc.

Neither the Demo Rev C board nor mine have that ... I am on my way out to see a client to deliver some work I did for him. I will give it a try later today.

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cheers ... brian riley, n1bq, underhill center, vermont
See the K107 Serial LCD Controller at
www.wulfden.org/k107/

bambino

Brian,
The 5Volt pin was added to give power to some monitors that have extra periphials that make use of the voltage there.
I did not include it, or the leds in my demo board and it did work just fine.
This is discussed in one of the threads, I remember because I asked the same question.
I found it but it is not much more help: http://forums.parallax.com/showthread.php?p=612272

Post Edited (bambino) : 12/27/2006 5:20:55 PM GMT

Brian Riley

Thankyou, that was mor helpful than it may seem!

... well, then, I must have a short or an open ... time to go back and check it out again ... more thoroughly as if I hadn't done it once already.

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cheers ... brian riley, n1bq, underhill center, vermont
See the K107 Serial LCD Controller at
www.wulfden.org/k107/

Areal Person

I wired up a propeller (DIP version) with VGA output on my breadboard

I did not use any LED's and it worked. I hooked it up to a regular VGA monitor.

If you can't get it to work, try a scope on it, checking the VGA signal.

It is possiable for it to be able to flash LED's etc. but yet for the VGA signal

to not be working correctly due to chip failure from ESD damage etc.

That's what my problem was.

-Areal

(I can't get my post not to double space )


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I have a tree growing out of my head, but

what do you expect ? I'm a programmer.

Newzed

To single space, hold down Shift and press Enter.

Sid

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Sid Weaver
Don't have VGA?

Newzed@aol.com
·

parts-man73

Looks like you already received this info but.... I also use the VGA interface sans LEDS with no problems on my SpinStudio VGA module. Sounds like you might have a bad solder joint or PCB trace. I made up many copies for my beta-testers and one of the VGA modules gave weird colors when I ran tests on the hardware, turned out to be a bad solder joint. White Text on a Blue screen turned into yellow text on a black screen.

Sometimes bad solder joints don't show themselves on an ohmmeter. I have had things check out with the minuscule current from my meter, but fail under a real load.

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Brian Meade

"They who dream by day are cognizant of many things which escape those who dream only by night" - Edgar Poe