I thought I'd share with you my latest project to build a portable gaming console. It has two main functions:
1) A portable console with a real joystick / buttons and a ~5 hour battery life
2) A gaming deck for TV play
The hardware is Sanwa and wired directly to the GPIOs. For the 10 inputs required for a joystick, 6 buttons and the SPI LCD you need to solder header P5 onto the board (gives an additional 4 GPIOs). Ill probably add 2 more buttons in the future using the UART pins giving a total of 12 control I/Os.
The stock RetroPie is used but the kernel is replaced so as to support the SPI LCD for portable use (fbtft).
I didnt manage to find a case I liked for it so I used two sheets of perspex with 40mm spacers. This works very well and allows you easy access for debugging / future mods
Let me know if you have any questions or want to make your own. Happy to share any details.
Pictures of the build: