I'm right in the middle of installing everything into my Miata.. I should have more pictures this weekend.

My software is written for the 3100/3900 series Noritake displays.. The command set is very similar to some of their other ones like the 7000 series, but the one foxtrot_xray is using is totally different (and far simpler). It's fairly primitive at the moment (blitting by pixels changed, or the entire bitmap, etc), and really needs to be improved because I've painted myself into a corner speed-wise by choosing a display that's 4x the size (256x64) and only 38,400bps .. But I have some evil plans for the extra screen real-estate.

... that means you could theoretically (depending on how the VFD wants its graphics inputted) get about 28 frames per second. That's not bad. And it could become a full display extender at that point.

And that's just the simple way to do it (or the worst case).. depending on the command set of the chosen display the drawing can be optimized significantly.

Well, not exactly..
For every bit, you'd have to send:
3 characters to set the position, then 1 character to turn pixen on or off.
4 characters per pixel. (At lowest efficency, of course.)
This would drop that down to roughly 6 frames/second.

Is that because the VFD doesn't support some kind of "blit" mode where you simply send it an ordered array of pixels?

The K610a does have commands to draw bitmaps by sending data either horizontally or vertically (0x18 and 0x19).. the 3900 and 7100s only do vertical, which is bloody annoying. I've attached the spec sheet for the K610a in case anybody wants to look at it (can't remember which are on their site and which you have to ask them for).

I don't think that splitting the Tx/Rx wouldn't work at the moment. I think that GPSapp will balk if it can't open the serial port. Maybe I'm wrong.

Right now I have separate apps for blitting to my VFD and receive commands from the joystick.. they seem happy enough sharing the serial port (with the same code used to open it in each).