I have built this little setup, which is supposed to record and replay input from a classic 9 pin Joystick. I connected the 9 pin connectors with the Arduino, read the input on the left side from the Joystick and then pass it to the right side by setting the corresponding pins to high.
It does work and I can play games on the Commodore 64. However, I noticed that with this setup, current is passed to the Commodore 64, which is very likely harming the machine a lot (I stopped immediately after noticing).
So my question is: how do I need to modify this setup so that no current is going from the Arduino to the Commodore 64 anymore?
Picture of the setup
Any advice is greatly appreciated, thanks in advance.