Controlling electronics with the Commodore 64 user port - Part 1
Arduino Project: Commodore 64 interfacing across the user port
RS232 on Commodore 64 | Connect C64 with a PC | Easy way
C64 User Port - a trivial example
C64 - Connecting devices safely to the user port - Arduino data transfer
Controlling The C64's User Port
Commodore C64 Nunchuk Adapter (Use Wii controllers on C64)
Is This The Only C64 Cartridge You Ever Really Need?
C64 userport, controlling 12 bits
C64 Opto Isolation User Port to Ardiuno part 1
Blink an LED with the Commodore User Port: C64 Electronics Programming Part 1
C64 User Port Light Detection
C64 User-Port Expander - Build Up
C64 Hardware - WIC64 - Wifi user port modem
About the ALDI Commodore 64
C64 userport 10 parallel bits
C64 Opto Isolation User Port to Arduino Part 2
Alien Group Voice-Box (user port hardware) for the C64
Arduino Project: Part 2 of Commodore 64 interfacing across the user port
PLATOTerm on real user port c64 hardware.