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 Atari 7800 (Pro System). The main reason I've not played much on this system have very much to do with the quality of the controllers, at least the two official variants I've tried have been absolutely dreadful.

The solution to my aching hands was replacing the controller entirely. Earlier I've been using the Sega Mega Drive/Genesis with a suitable adapter, but now you can put down the Sega-branded controller and use the C64 JoyKEY instead! With clicky MX-switches it's a better solution for playing these games as you get the tactile and audible feedback you need to really get into the games released for the system (if you ask me). The third fire button will not be used for anything in this setup, but for all those Atari 7800 games that supported two fire buttons - you'll have those ready and awaiting your next move! This adapter can also be used to play on an Atari 7800 using a Sega Master System controller, just wire up a male DB9 IDC to 2x5 pin IDC cable with pin 1 in the same place.

If it wasn't perfectly 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.