CPLD replacement for ZX8301

[lliont]

Two commands for 16 color support in mode 8 are ready.

To enter the 16color mode: poke 98400,1

The first command is PLOT x,y,col sets the point at x,y to color col.
x,y take values 0..255, left down corner is 0,0 and col = 0..15

The second is COLSUBS x1,y1,x2,y2,col that replaces pixels with color col in the defined rectangle with the lighter version of the color
x1,y1,x2,y2 take values 0..255, left down corner is 0,0 and col = 0..7
x1,y1 is the left down corner and x2,y2 the right up corner

This is a test of plot command again in composite video & crt because although it does not produce the best picture it is convenient for me (it's on my desk ).

[Cristian]

Increasingly interesting...

[lliont]

I made the pcb that has a 2 bit resistor dac and an AD724 video encoder.
The new composite video output is better and sharper but not perfect as it still has a little noise. The nice thing about it is that you don't have to add 3 resistors to the QL motherboard and can easily take it's output using the RF out RCA as video composite out.
The pcb also provides a scart output with the 16 color support.
The 2 bit/color dac gives some new color shades it is an improvement but small. It also gives a low and high brightness level output option to both standard video modes.

Using different bit weight for the 2 dac bits by changing resistor values can obtain different color differences between the dark and light colors to match one's taste.

[lliont]

Composite video CRT:

Composite video LCD:

The noise in the composite video signal was drastically reduced when instead of one 10uF electrolytic capacitor (C2) I used 2x 4.7uF ceramic multi-layer capacitors in parallel.

[Andrew]

Why are the colors different between CRT and LCD?

[lliont]

I suppose it has to do with the monitor/tv settings and probably with the camera.
Brightness setting was set higher in the crt.
With naked eye the the light yellow in the crt monitor looks very light yellow but in the photo it looks almost white.
Also this small lcd tv I use for tests is darker on top and brighter at the bottom of the screen.

[Andrew]

With naked eye the the light yellow in crt is very light yellow but in the photo it looks almost white.

I thought it was the standard color white!
Well, when will you produce a batch of replacement ULAs? I believe I'm not the only one who wants to buy one

[XorA]

When does Derek start assembly of them

[lliont]

I think I'm near the final version.
I'll find out the cost to produce a bunch of assembled pcbs and we'll see.

[Andrew]

Would it be too difficult to have 8 colors in mode 4?