I said I’d post an update (with a picture) when I got the VGA console working, so here it is:
It’s very preliminary; the screen does not scroll yet, and input is still coming from the serial port (there’s no keyboard port yet), but it does work.
One thing that is rather apparent in the above screen shot is that the weird issues with some of the punctuation symbols. I’ll dig into that after I get scrolling working.
Hardware Changes
The image above was taken using my updated hardware design that I talked about in my last post, which uses clock stretching in lieu of the 65816 RDY pin to pause the CPU during propeller accesses. The previous design rarely lasted more than a few minutes without random serial port garbage, and always crashed after a few hours at most. This new design has so far gone nearly 48 hours glitch-free, and probably would have gone longer had I not powered it down for a ROM update.
Next Steps
With basic video output working my next task is to make the console scrolling work so that it’s truly usable. After that I’ll be getting the keyboard port implemented, which I’m still planning to do using a small ATmega ‘328. It’s going to connect through the VIA so it should be a lot less work than it was getting the propeller implemented.
Stay tuned for another update later this week.
