keenerb wrote on 2020-02-06, 00:18:
I've got a dead Tandy 1000 I'm contemplating transforming into a "virtual" tandy with pcemu or a similar application, but using a Tandy CM-11 would necessitate CGA-compatible monitor signal.
Perhaps it's possible to use the GPIO in some fashion to do this since CGA is a digital signal?
Anyone have any info on a similar project?
I haven't played with it, but it looks like it should be pretty easy using the Pi's DPI facility: https://www.raspberrypi.org/documentation/har … i/dpi/README.md . It's just a matter of connecting up hsync, vsync and 4 of the signal output pins to R, G, B and I. Some voltage conversion might be necessary - I'm not sure offhand if a Tandy CM-11 will recognise 3.3V as a "high" signal (no harm in trying). On the software side you'd need to set dpi_timings and other display parameters in config.txt - I can probably help you figure out what those numbers need to be if you want to go down that route.
As for a modern PC, I have recently been experimenting with doing digital IO using a cheap Cypress FX2LP USB development board. I have input (i.e. digitising an RGBI signal) kind-of working. Generating a signal should be similar, but I haven't tried it. It's possible that some modern graphics cards can be coaxed into generating a 15.75kHz/60Hz output but you'd need some non-trivial hacking to convert such an output to RGBI.