Crap, I forgot to include the joystick cable, at least some of you should recognize that purple board.
That combo, if you have it, is backwards compatible with this "MCP add-on", as well as the cart itself. They just need re-flashing.
I mostly just wanted to prove a point and made it for myself, still a bunch of code to write. Maybe I'll route a proper PCB for it. Maybe not.
1.) One man operation, for hardware and software, like KH.
2.) Own money on R&D.
3.) Limited time between RL, babysitting a bunch of adults on a forum and working 10 hours a day.
4.) Many processors involved, because I want something I know will run on EVERY 7800, without a hitch.
5.) No profit.
6.) No underpant gnomes. But the sock gnomes are out in force!