VGA Operations

gmkuka

Using a ViewSonic 15" 1024x768 LCD monitor I found the following...

On a 'DemoBoard'· "VGA_512x384_BITMAP_DEMO", "VGA_DEMO" and "VGA_TEXT_DEMO" fly well...
························ "VGA_HiRes_Text" does not fly at all...

On a 'ProtoBoard'· "VGA_512x384_BITMAP_DEMO" works fine, But...
(W/VGAConnKit)···"VGA_DEMO" and "VGA_TEXT_DEMO" And "VGA_HiRes_Text" do not fly at all...

I confirmed continuity from the holes labeled P16..P23 to the connector and all the Res's are well within tolerance...

The monitor bark's with a 'No Signal' or 'OutOfRange' display...

Any Ideas...

gmkuka

James Newman

I just had the same type problem, and since it was my first soldering attempt, got a bit scared

I hadn't soldered on the 470Ohm and 100Ohm resistors, put those on, and it worked fine.

I couldn't actually find anything that said to put those on, anywhere on the site. There was a link to something on the old web pages' shop, but not on this one... not sure... anyway, I looked at the diagram for the Demo board to figure it out. The board has '470' between the 3 places for the respective resistors, and '100' (though hard to see) between the 4 places for their resistors.

If you've already got those, and they have good joins, then idk. Hope that helps.

Rayman

There are detailed instructions on those resistors here:

http://www.rayslogic.com/propeller/Propeller-ProtoBoard-v1.1.pdf

This file is on the Parallax site somewhere too, but I'm having trouble navigating their new web site...

Fred Hawkins

I'll second that criticism. Reminds me of my cable tv company -- things get worse. (always for them, hope remains for Parallax)

gmkuka

Thanks for the responses...

Can anyone explain why the 512x384 Tiled display, which is setup in the 1024x768 mode at 66Hz,·would work on the ProtoBoard and the other 1024x768 60hz display programs donot??? All the colors and obiviously the 'Syncs' are there... I see the various shades of Red, Blue & Green and their combinations.

All the programs are·directly from the 'Propeller' folder, as supplied by Parallax...

This defies rational explanation, so far! The only·hardware difference I see is the 'Led' Terminations on the 'Demoboard'...

Any ideas/comments would be greatly appreciated...

gmkuka

Mike Green

Some displays are really finicky about what combinations of resolution and scan rates they will accept.
Since the Demo Board and the Protoboard use the same connections for VGA output, the same programs
should produce the same results on both boards. If not, I'd check the solder connections on the Protoboard.
There might be a poor connection whose signal might show up on an oscilloscope or logic analyzer, but fail
under higher load from a VGA input on a monitor.

Ken Peterson

I tried the standard VGA driver from the OBEX with my monitor and it didn't sync up until I started playing around with some of the values. I think I changed the pixel rate a little. Make a note of what your original values are before messing with them.

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The more I know, the more I know I don't know.· Is this what they call Wisdom?

gmkuka

After going over the p16 .. p23 pins with an Oscope, it was determined that the protoboard did not output signals according to the plan... Cannot explain... I added a 'Toggle P0' in various stages of the program, all with different 'Freqs' to determine which one is flying... A bit tedious, but it worked... The Propeller did not make it thru·the initial cognew successfully... Meaning effectively no cogs available... Therefore none of this video stuff flies... I happened to take advantage of the new price and bought 5 of the protoboards... So I took the next one out to see what it did... Effectively, it did nothing wrong...· syncs and the RGB stuff were on a Par with the DemoBoard measurements.

I can only say the·first protoboard must be broken,·in some way... I confirmed the connections, loaded w/75ohms each, to be in good shape and unloaded acting according to the untermed ratios... To make these measurements I used a virgin copy of the test program (·vga_demo.spin ) on both devices... When I measured the 'H' sync pulse on the protoboard it was ~5usec wide on ~33usec intervals... A negative going strobe :·5us Low / 28us High... The demoboard had the same timing except it generated the inverse, ·a positive going strobe and it works... This may be·a clue to it's brokenality...

Gotta get on with the project... Thanks for all your help...

gmkuka