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 using it on your Sega Mega Drive/Genesis console instead!

The adapter when connected converts the C64 JoyKEY into a real 3-button controller, even using the same exact electric components that were found inside them. So if you've ever wanted a Sega Mega Drive controller that used Cherry MX switches instead, well - now you can have one by adding this simple adapter. One caveat is that the C64 JoyKEY is lacking one button, for that reason the start button has been placed directly on the adapter instead. The arcade edition of the C64 JoyKEY, does however allow you to add extra buttons and there is a jumper header for choosing which one of these will be used as the start button. Note that the Sega Mega Drive and Genesis controllers have recessed controller ports, which means that normal DB9 connections can't be used with the system - for that reason I recommend picking up a straight IDC to DB9 adapter in order to get around that issue.

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.