TRS-80 Model I emulated on a PIC32MX processor. It provides VGA video and PS/2 keyboard so as to be usable with commonly available hardware to-date (well, PS/2 keyboards are becoming rare, but it works with a USB-to-PS/2 adapter as well).
I did this project to keep myself occupied while recovering from some surgery in 2015, for which I would have limited mobility for about a month. I didn’t think I’d be up to doing bench work, so I used some existing PCBs to allow me to focus on the firmware, which I could do lying down (both literally and figuratively). I used a UBW32 (from Schmalzhaus) as a CPU ‘breakout board’ and also a UBW32-MCC (from Dontronics) to provide the VGA, PS/2 keyboard, SD card, and power connectors. Later, I supported another board: the Olimex Duinomite-mini (and reportedly the Duinomite with the IO board). The Olimex boards are much easier to come by, inexpensive, and ready to use out-of-box. But no color :(. But, hey, the TRS-80 Model I was a monochrome, anyway! (I just like the green screen effect.)”