[Kevin] just finished a project for someone who lives in his apartment complex. This resident loves the game Pop ‘n Music – a Guitar Hero sort of game for the original Playstation and PS2 that uses nine colored buttons instead of five buttons along a fingerboard. His original idea was to wire up a few arcade buttons to a Playstation controller but this plan fell through, forcing [Kevin] to figure out the PSX bus all by his lonesome.

The initial code began with simply bit-banging the PSX controller interface with an AVR. This had a few problems, namely speed, forcing [Kevin] to move onto assembly programming to squeeze every last bit of performance out of a microcontroller.

The assembly route failed as well, dropping some transactions  Looking at the problem again, [Kevin] realized the PSX controller bus looked a little like an SPI bus. There were a few changes required – reversing the order of the bits, and using the MISO line to drive a transistor – but this method worked almost perfectly on the first try.

Now, [Kevin]’s building mate has a custom Playstation controller for his favorite game. Of course all the code is up on github for all your PSX controller emulation needs, but be sure to check out this completely unrelated Pop ‘N Music video from someone who desperately needs a piano.