Came across this link of a ZX81 emulated on a Teensy 3.6 https://forum.pjrc.com/threads/54127-ZX ... controller
I have a 3.5 so I haven't tried it. I did post a question on the Teensy Forum about making the 3.5 into an ULA and they think it may be possible https://forum.pjrc.com/threads/53693-Hi ... terrupting
Teensy ZX81
Teensy ZX81
2X Timex Sinclair 1000, ZX81, ZX80Core, 5X 16K Ram Pack, ZXBlast, ZX P file to Ear Input Signal Converter, Elf II