C64 User-Port Expander - Build Up
Commodore 64, EX64 Port Expander experiments.
Commodore 64. Port Expander unboxing and surprise :)
Is This The Only C64 Cartridge You Ever Really Need?
Controlling electronics with the Commodore 64 user port - Part 2
C64 User Port - a trivial example
Commodore 64 SFX Sound Expander - In Depth Look
Arduino Project: Commodore 64 interfacing across the user port
C64 on trial: Is it any good as a serial terminal?
VIC-20 Super Expander and EPROM programmer
Controlling The C64's User Port
C64 - Connecting devices safely to the user port - Arduino data transfer
Dorktronic Commodore 64 User Port GPIO & GPIOTracker Software
Commodore 64 User Port to solenoid
Budget Upgrade Magic: The $10 RAD Expansion Unit for C64 - Boost Your Retro RAM!
64 Commodore 64 Cartridges: Expansions, Interfaces, Utilities, Games
C64 Opto Isolation User Port to Ardiuno part 1
Commodore 64 (C64) Datalux SV-703 Cartridge Expander - Teardown / Repair
FM-YAM Sound expander - Commodore 64