Console hardware has always fascinated me, and for some reason, I never wanted to accept the limitations that I was given by console manufacturers. It was for that reason and for the sake of learning, that I decided to take on a project that would allow the Sega Genesis controller to be used with a Turboduo or PC Engine. While it's not exactly the kind of adapter that is in high demand (otherwise the manufacturers would have made it long ago), it was a good learning experience. Not only that, but it provided an avenue for me to use a controller more commonly available in the U.S. with NEC's underdog console.
The project consisted of making an adapter out of a small project box with a DB9 connector and an old MAC serial cable. Above are a few pictures of the project and below are two files that will be of interest to those wanting to know more about the project. The first is a rough parts list. The second is a schematic to be used with Eagle PCB circuit design software.
Although work on the project has stopped at this point, there is one known bug that is worth mentioning. During the prototype phase of the project, the adapter was only tested on a couple of games, without issue. However, a wider array of games were used in the final testing. One game in particular, Ordyne, displayed an unforeseen problem. When playing the game with the adapter, the console will seemingly randomly reboot. After further examination, it appears that the adapter is perhaps sending both a left and right symbol to the console at the same time, which the game may be interpreting as invalid input, thus initiating a reboot.