“Interface a C64 with an Arduino using Firmata.
This is a Firmata client implementation for the C64 using the userport at 2400 baud for communications.
Prerequisites
You’ll need:
x64
Arduino UNO
Grove shield, servo, button, LED, potmeter, relay
Optional:
DIY for the Grove stuff
A real C64
A way to transfer the program to the C64
Userport connector
Wires between the C64 and the Arduino UNO”