ThomasHarte wrote:RobC wrote:Agreed. I'd love to create an improved video ULA to give 16 proper colours in mode 2 and a larger palette. I have the components ready and finally have the time on my hands but now I've gone and broken my wrist
I'm an electronics dunce, and have recently evidenced this elsewhere, but surely the problem isn't the ULA? Red, green and blue come out as digital signals down in the lower right of the schematic, then a bunch of logical components do the resulting mixing to produce video, seemingly in a binary fashion? If you added a brightness pin, or made those ULA outputs analogue, surely you'd also have to change a whole bunch of stuff in the trimmed schematic hastily edited and attached?
Not really - you would ignore that part of the circuit and take the (now analogue) RGB and sync signals out to a monitor by a different connector (or wired direct to the existing RGB output). The issue with the ULA is that it does the serialisation and palette look-up. If you want to do 16 proper colours in mode 2, it needs to be replaced or augmented.
My idea was to use a Brooktree BT450 RAMDAC which has a 16 x 12-bit palette to give 16 colours from a palette of 4096 (16 shades of red, green and blue).