VGA demo

retromicro · 2014-09-06 11:00

Hi

I've got my homebrew Propeller board set up with a VGA connector as shown below

Pin 16 = 220R = Vertical Sync

Pin 17 = 220R = Horizontal Sync

Pin 18 = 470R = Blue Video

Pin 19 = 220R = Blue Video

Pin 20 = 470R = Green Video

Pin 21 = 220R = Green Video

Pin 22 = 470R = Red Video

Pin 23 = 220R = Red Video

I'd hoped that I could just load the Propeller Tool, Open VGA_Demo.spin, do a Run / Compile Current / Load RAM and then see video on the VGA monitor. Nothing showing though. My Hello World code runs fine via the serial terminal so I know the hardware basics are ok.

Is there something obvious missing from the above ?

Thanks

PS I've also loaded the microphone_to_vga demo. I see that you then start off with one tab. However, if you do a Run / Complie Current / Load RAM, you see another level of code in the top left hand corner of the Propeller Tool. VGA_512x384_Bitmap has appeared and the same shows in a new code tab. It looks like this happened because there is the below entry in the initial code

vga : "vga_512x384_bitmap"

Does all the code on both tabs get compiled and sent to the Propeller when the compile is done ?

This code also seems to default to pin 16 as the base pin so I'd expect this to work.

Duane Degn · 2014-09-06 11:29

retromicro wrote: »

Is there something obvious missing from the above ?

Do you have the Propeller's ground connected to the VGA grounds? I see five ground connections on the Propeller Demo Board Schematic (available from the Prop Tool's help menu).

retromicro · 2014-09-06 11:36

Thanks for the reply. I have 5,6,7,8 and 10 connected to ground.

These match the ones in the diagram. I have NOT got anything connected to pin 9 (+5v). I read about this pin and was under the impression that this was used to supply the monitor for ID purposes and I would get away with out it.

Duane Degn · 2014-09-06 11:50

retromicro wrote: »

I have NOT got anything connected to pin 9 (+5v). I read about this pin and was under the impression that this was used to supply the monitor for ID purposes and I would get away with out it.

This might depend on the monitor you're using. I don't know enough to be sure but I'd try to follow the schematic to the Demo Board before trying to make changes.

I know I've used "VGA_Demo.spin" on the Demo board and it worked fine. As long as "VGA_Demo.spin" is the active tab when you press F10 or F11, it should be the only code to compile and load into the Propeller.

Bill Henning · 2014-09-06 12:53

Do you have a 5MHz crystal connected to your prop?

retromicro · 2014-09-06 13:09

Bill Henning wrote: »

Do you have a 5MHz crystal connected to your prop?

Yes thanks.

Electrodude · 2014-09-06 17:26

Did you try a different monitor? Lots of monitors, especially LCDs, don't like certain resolutions. Try a CRT if you have one - they'll usually take almost any signal you give them.

retromicro · 2014-09-06 17:32

Adding 5v to that pin made no difference but I have since seen a VGA signal being generated.

I've changed the monitor.

I used the VGA64 Bitmap Demo by Kwabena W. Agyeman and every now and then, I could see the polygon changing shape and moving around the screen. I could change the colour in the code.

However, I'd get so many frames and then the screen would go blank for a while. After a while, the picture would come back.

While the image was on the screen, it was steady and clean.

I also ran the standard VGA demo a few more times and saw, very briefly, 'woof' on the screen.

Does the above suggest anything in particular ?

Thanks

Electrodude · 2014-09-06 20:47

retromicro wrote: »

Adding 5v to that pin made no difference but I have since seen a VGA signal being generated.
However, I'd get so many frames and then the screen would go blank for a while. After a while, the picture would come back.

While the image was on the screen, it was steady and clean.

Sounds like an LCD that can't lock onto your signal for very long and keeps losing it and then locking on again. I'm pretty sure an LCD monitor I have didn't like VGA_Demo.spin or vga_512x384_bitmap.spin's timings. Your monitor might not like 512x384, even though it's half of 1024x768. Try to find a CRT (the old fat kind) to test it on - if the CRT works and doesn't lose the signal, it's a timing problem, otherwise, it's something else.

Duane Degn · 2014-09-06 21:19

Electrodude wrote: »

Sounds like an LCD that can't lock onto your signal for very long and keeps losing it and then locking on again.

Now that you mention this, I recall I also had a LCD monitor which didn't work with the Propeller. Most of the VGA screens I've used have worked with the Prop but I have one which doesn't.

shimniok · 2014-09-07 09:58

I've definitely seen some demo programs not work with some of my monitors.

jazzed · 2014-09-07 12:02

IIRC ...

kuroneko's drivers work with most VGA monitors. Don't see any in the OBEX though.

Tubular · 2014-09-07 15:31

jazzed wrote: »

IIRC ...

kuroneko's drivers work with most VGA monitors. Don't see any in the OBEX though.

http://forums.parallax.com/showthread.php/138654-FYI-VGA-100xH-P-dual-cog-per-cell-colour-(full-indexed)?highlight=100xp

retromicro · 2014-09-08 09:54

Thanks for all the suggestions. I had an idea what else it could be. I was powering the prototype board from the USB to serial adapter 3.3 volt line and wondered if the monitor was sucking the line dry.

I added some voltage regulators and connected a wall wart and lo and behold, everything started to work. All but one of the demos work and the monitor cannot handle the signals generated by the last one.

I'll have a look at the work done by kuroneko.

kuroneko · 2014-09-08 17:19

retromicro wrote: »

I'll have a look at the work done by kuroneko.

This search should cover it. Any problems just let me know.

kuroneko · 2014-09-21 02:45

I'm also in the process of moving my (video) stuff to github (not finished yet).

VGA demo

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