53 minutes ago, rje said:
Here's an ATMega solution: https://github.com/fachat/XD2031
Or, perhaps what Tom was alluding to: https://github.com/Larswad/sd2iec_mega2560
I have a Mega 2560 and a Nano as well, so that's fine, they're just not as familiar to me.
The Arduino IS probably better; for one thing, the voltage levels are more compatible.
There's also https://www.insentricity.com/a.cl/208/C64PiVideo.
Oh, I'm stuck on the Pi because
(1) I "know" it better than other little platforms and
(2) I have some lying around but also
(3) The Pi Zero is just so cheap and
(4) I get stuck on things.
Yes, I was thinking of the sd2iec_mega2560 version - although I would not implement it on a Mega. I would use a Teensy 3.5, due to the built in SD reader and smaller footprint.
Actually, you should be able to do it on a Pi, using a bare metal coding solution like Circle. Just don't expect to do this in Raspbian. Pi 1541 was developed as a bare metal program specifically because Linux doesn't have the timing resolution needed to work in this situation.
Most of the code should also work, although you may need to deal with the timer - I don't know what the Pi uses for a timer, but you need some pretty tight precision if you're going to use a serial connection. A parallel connection would actually be simpler to code, since you just need to set the data pins and strobe the clock pin.
I also have RunCPM running on a Grand Central - which would actually be ideal. It has a lot of pins, so you can stick it on the User port and also use it as a serial and WiFI breakout, with the addition of an ESP8266 or ESP32.