[Coco] MC6847 VGA Board Project (non-FPGA)

[Zippster]

Hello everyone,

I’ve posted a bit about this on the Facebook group, but I know not everyone from the mailing list uses it.

Thought I’d share a little bit about a MC6847 to VGA project I’ve been working on.

The theory is that the board uses comparators configured as a ADC on the component video outputs from the MC6847 to
break the signals down.  From there a CPLD is configured to convert this output into digital RGB.
This in turn is run through an Analog Devices Video DAC where the video is output in analog RGB at VGA scan rates,
using a new pixel clock generated by the onboard clock circuit (per Analog’s data sheet specs).

I fully expect there will be some debugging, but I think it’s looking pretty good so far.

Here are a couple of pics of the board layout, and a (mostly) assembled prototype.
I didn’t have a particular cap value on hand, so prototype testing will be after my next shipment of
parts from Mouser.  Hopefully it goes well.  :)

Layout <https://drive.google.com/open?id=0B1sgl615FlGnQzdwTFJsNTRKLWM&authuser=0 <https://drive.google.com/open?id=0B1sgl615FlGnQzdwTFJsNTRKLWM&authuser=0>>
PCB <https://drive.google.com/open?id=0B1sgl615FlGnYjdzNEpGSnZiWm8&authuser=0 <https://drive.google.com/open?id=0B1sgl615FlGnYjdzNEpGSnZiWm8&authuser=0>>
Populated (mostly) <https://drive.google.com/open?id=0B1sgl615FlGnME4tYU1EdzdDQTQ&authuser=0 <https://drive.google.com/open?id=0B1sgl615FlGnME4tYU1EdzdDQTQ&authuser=0>>


- Ed