Button one is wired to pin 6 of the DB9 connector, this is standard for most retro computers. I have also added an extra button.
Commodore 64 Cassette Gas Kit 64 - "ANIROG" - RARE Accessory Tested and Working
Commodore 64 C64 Games - Various - Multi Listing - Small Tape - Fun
8Bitdo M30 2.4G Wireless Gamepad + 9 Pin Receiver - Commodore 64 Amiga 3DO WOW!!
Sega Mega Drive / Genesis Controller Pad to Amiga And Commodore 64 C64 Adapter
Sporting Triangles Commodore 64 Game Cassettes