I go over the custom gamepad controller I made to use with Retropie Emulation Station.
The joysticks, wiring, and buttons were purchased from FocusAttack.com. I used the Sanwa JLF-TP-8YT joysticks and Happ Competition buttons.
The Control block which is used to connect the Joysticks/buttons to the Pie can be found here: www.petrockblock.com/product/...
And for the Emulation Station RetroPie setup I used retropie.org.uk/ Everything you need is on that web page, but I also made a post a few years ago about it on my website which helps you navigate through the necessary steps for a complete working system.
802projects.com/retropie.php