You're welcome =)

As noted in the comments of that post, I'm doing a raster display with vector display techniques. Opamp sweeps are indeed a more sensible way of rastering, but the internal DACs on this microcontroller are fast enough to keep up anyway.

What's killing the refresh rate is the settling time for the (crappy) external dac doing the 4-shade colour. Your terminal application only deals with beam on/beam blanked so you can run it a lot faster.

By all means give it a go, it's a pretty satisfying project. I have no doubt you can improve on my version.