Looking for a very simplified VGA example.

handermanntr

Hello,
I have been attempting to get a simple VGA single screen color driver working in asm, and I can't seem to get it to work. I have been trying to do it by modifying existing drivers, but they are all to complicated for me to modify to do this simple thing. i am wondering if anyone can supply a completely stripped down driver(IE. everything statically set for an 80MHz clock, any resolution, single color screen, minimal settings). Basically, I am wanting to learn how it works, but they existing ones are too complicated from all the different settings.

Also, if you cant supply this, maybe someone can answer these questions:
1. Do you have to provide a specific clock via CTRA, or will any reasonable clock work(IE, can I clock it at 80MHz, or does it have to be specific for a format), and if it does have to be specific, can someone supply a table of these?
2. Can someone supply an equation that I can use to calculate FRQA to generate a specific frequency with PLLA internal(Ignore PLLDIV, say it is just VCO/16/equal to the input clock)
3. How exactly are the Vsync and hsync signals generated via code?
4. If during the active video pixel clocks I use waitvid with $0000_FC00 for colors, and $FFFF_FFFF for pixels, should this display a full white screen?

Thanks!

tonyp12

My barebone is very simple, though it uses waitcnt for sync instead of h & v pixels
http://forums.parallax.com/discussion/134552/barebone-vga-driver

handermanntr

Thanks! I am looking more for one that uses the video generator though. Thanks for the reply!

ericball

You might want to look at my NTSC drivers to better understand how the video generator works.

Also, if you cant supply this, maybe someone can answer these questions:
1. Do you have to provide a specific clock via CTRA, or will any reasonable clock work(IE, can I clock it at 80MHz, or does it have to be specific for a format), and if it does have to be specific, can someone supply a table of these?
- You need to calculate FRQA to give the desired pixel clock

2. Can someone supply an equation that I can use to calculate FRQA to generate a specific frequency with PLLA internal(Ignore PLLDIV, say it is just VCO/16/equal to the input clock)
- See AN001 Propeller P8X23A Counters

3. How exactly are the Vsync and hsync signals generated via code?
- For VGA, HSYNC & VSYNC are simply periods with the HSYNC & VSYNC bits in the output byte set or cleared to generate the appropriate signals. The Propeller Video Generator doesn't know anything about HSYNC / VSYNC, you just set the VSCL to generate the appropriate number of pixel clocks, and WAITVID the right bits.

4. If during the active video pixel clocks I use waitvid with $0000_FC00 for colors, and $FFFF_FFFF for pixels, should this display a full white screen?