Nowadays, PCs don’t have a PS/2-interface anymore. I’d base a project like this on microcontrollers if I would do it again, and interface the computer via USB. So I leave the details in the past and give just a short description of the project.
At that time, I was interested in MAME, the Multi Arcade Machine Emulator. You can play all the old arcade game classics with that. A PC keyboard is not the ideal interface for thos games, so I started building my own controllers.Originally, the joysticks were sold to fit a Sega Dreamcast console. I threw out the electronics and implanted a PC keyboard controller instead. I had to find out the keyboard matrix layout and interface all the joysticks microswitches to the right contacts on the controller board. Not too complicated.
The second player’s contacts were connected to a second unit with an old serial cable. Additionally, I built a Y-adapter for the PS/2-interface, so I was able to control the PC outside of MAME.
The result surely wasn’t a pretty build, but: it worked.
Nowadays, I don’t have a PC with a PS/2-interface anymore. I already dismantled one of the joysticks and built something else. But that’s a different story…