In this video, Jan builds two different versions of Pi hats that allow the Raspberry Pi to be connected to Commodore hardware. He also takes a look at setting up an SD card from scratch and fiddle a bit with the options.txt settings. A bit of a trial-and-error tutorial if you will.
The SD2IEC is an open source SD storage solution for Commodore computers that uses a micro controller and some custom software. The firmware is available here: https://sd2iec.de