I have made two boards at home for this project. One is for the PTH version with attiny85.
The other board is two sided and it required a lot of patience to make the layers match as well as the drilling on the vias. The drill bit has only 0.6mm!
I've designed two versions of the board. One is specific for NES/SNES controllers and uses an ATTiny85. This version has two PCB variants, one using SMD components and another (single sided) using PTH components.
The other version uses an ATMega*8 (8/88/168/328) and it is designed to allow several types of controllers to be connected.
Schematics
The schematics for both versions are shown below. All files are available for download.