With the C64 JoyKEY I wanted to build a simple joystick, but given how well it worked I wanted it to work with more than a handful of systems. You could certainly use it directly as a three-button joystick for the Commodore 64, this module is however not really about the Commodore 64 - it's all about the Sega Master System. It's a system I absolutely love and while the original controller is perfectly fine, they are getting rare to find in good condition and for some of the games you really need the added feedback of the clicky switches that my C64 JoyKEY provides!

The Sega Master System itself only had two buttons, so the third one will not be used by anything in this setup. There is however the option of moving the jumpers on the adapter itself, this allows you to swap the first and second button - perfect for that "other" weird version of Alex Kidd in Miracle World where the buttons are swapped.

If it wasn't already clear, this is only an adapter for the system and not the joystick itself - for the main PCBs as well as other adapters you might be interested in, check out my other shared projects relating to this project. For BOM and build instructions, have a look at my github-repository.