Color code tables for Propeller Video

Genetix

Several drivers state that Graphics Palette has a Color Code chart but I don't see anything in the code.
I am trying to decipher Chip's demos so I can use them but few of the colors are documented.

PropGuy2

I have done a lot with the VGA color palette code. However given the different program code samples and how your VGA screen is set up, it is sometimes best to sequentially go thru the different color palette numbers and see what the colors look like on the screen. Generally I start with "000" (usually black, maybe white?) thru "999", as 000, 001, 002. etc. After a few samples, you can usually find a pattern in the colors. Remember also that there is one set of palette numbers for Foreground, and another for Background. Try it and see, hope this helps.

Rayman

I've got a table of TV colors here:
http://www.rayslogic.com/propeller/Programming/TV_Colors.htm

ericball

Rayman - there's actually another set of oversaturated colors.

When bit[3] = 0, bit[2..0] are sent to the 3 bit DAC, giving 8 levels: -40 IRE (sync) to 100 IRE (bright white) in 20 IRE steps with 0 IRE being blank / black. (IRE is the scale used when measuring TV signals.)

When bit[3] = 1, the DAC is driven with the value in bit[2..0] +/-1 based on the MSB of bits 7-4 plus a 4 bit counter driven by PLLA. From the TV perspective, for bit[3..0] = 9 to 14 this looks like a -20 to 80 IRE luma signal with a 40pp IRE chroma signal riding on top (with the chroma phase set by bits 7-4). (Note: as -20 IRE is below black, bit[3..0] = 9 generally not used.)

The fun is when bit[3..0] = 8 or 15 as now the +/-1 causes an overflow so the output is -20/100 IRE and -40/80 IRE respectively which is then decoded as 40 IRE or 20 IRE luma with 120pp IRE chroma (three times the color saturation). However, this also creates a phase reversal, which is why it generates a different color.

Rayman

eric: The top row in that graphic is the saturated colors. Are you saying there's another set of saturated colors?

If so, what are their byte codes?

The regular ones are: 08, 18 ... E8, F8

BTW: I think you also figured out how to use the other TV resistor to create more colors with a modified driver, right?

ericball

Hi Rayman,

Colors 0F, 1F ... EF, FF are the other set of super saturated colors.

Yes, see http://forums.parallax.com/showthread.php/126099-more-colorful-baseband-TV for the TV driver using the auralsub pin to increase the colors. (Although it wasn't 100% stable on all displays.)

Eric

Genetix

That TV chart is very helpful Rayman.

Genetix

I noticed that the newer Parallax VGA circuits use a buffer chip while the older ones don't. Does that have any effect on the display or video capability?

msrobots

I do not know of any buffer chip for VGA. Link?

Usually it is just a resistor array forming a simple DAC for TV and direct pins for VGA?

Except the C3 board. There you have a chip to use either VGA or use the pins by yourself on the header.

Confused?

Mike.

Genetix

If you look at the Propeller BOE (page 13 - U15) you will see that it uses a SN74AHC541 which is an Octal Buffer/Driver with 3-State Outputs.
https://www.parallax.com/sites/default/files/downloads/32900-Propeller-BOE-Schematic-Rev-A.pdf
https://www.parallax.com/sites/default/files/downloads/32900-Propeller-BOE-Bill-Of-Material-Rev-A.pdf
http://www.ti.com/lit/ds/symlink/sn74ahc541.pdf

The Human Interface Board uses a 74HC541.
https://www.parallax.com/sites/default/files/downloads/40003-Human-Interface-Board-Schematic-Layout-Rev-A.pdf
http://www.ti.com/lit/ds/symlink/sn74hc541.pdf

The VGA SIP Adapter uses a 74LVC541.
https://www.parallax.com/sites/default/files/downloads/28076-VGA-SIP-Adapter-Rev-A-Schematic-Layout.pdf
http://www.ti.com/lit/ds/symlink/sn74lvc541a.pdf

The older designs only had resistors.
https://www.parallax.com/sites/default/files/downloads/32100-Propeller-Demo-Board-Schematic-RevG_0.pdf
https://www.parallax.com/sites/default/files/downloads/32111-PPDB-RevA-Schematic.pdf (Last page)
https://www.parallax.com/sites/default/files/downloads/28075-VGA-PS2-Adapter-Board-A-Schematic.pdf

msrobots

I might be terrible wrong here. But to me this looked like possible double use of the pins for other purposes.

But looking at the schematics you provided I do not see any enable/disable function here like on the C3 board from Parallax.

So I am stumped and hope somebody with more knowledge could chime in.

As far as I know you do not need any buffers for VGA or TV. I started with a PE kit on breadboards and later used a lot of them 5-pack ProtoBoards(?) without USB. Never used any buffers there, and that was the beauty of it for me. Simple circuit and able to put out VGA or TV. The C3 was disappointing to me, since none of the usual drivers worked for SPI. Collecting dust now.

So now I am more confused then before I looked at them schematics.

Sorry to be of no help to you.

Mike