I've been playing around with my MSX computer recently, and as the computer itself supports a two button joystick I wanted something that'd support more than one button. Somewhat like the Commodore 64 and Commodore Amiga, a standard Sega Mega Drive (Genesis in North America) will damage the system - so we'll need to use an adapter with it. I found a great writeup and a lot of details for building one by FRS, so I built one based on the the information provided.

As keeping with other adapters I've made, I titled it MSX Mega Drive Adapter to keep with the naming scheme (this circuit is more commonly known as a JoyMega). I've made similar adapters for other systems, one is the Atari 7800 Mega Drive Adapter as well as the C64 Mega Switcher.

Check out my github-repository for the BOM as well as a somewhat detailed description on soldering it together.

https://www.pcbway.com/project/shareproject/Commodore_64_Mega_Switcher__Revision_B_.html