Modern joysticks offer some handy features and more precise control, but they are often incompatible with older hardware. This is where your standard adapters come in, but even these fail to account for some aspects of the vintage hardware.
This OpenC16 JoyAdapter is an open hardware solution for the Commodore 264 family. Since these older machines have a different protocol and connector, the adapter’s design was created with these things in mind. It allows you to use modern joysticks while also protecting the TED chip.
This is done using a buffer IC and limiting the current on the joystick lines, a similar strategy to the joysticks of that era. Many other adapters fail to offer this feature, leaving your TED chip vulnerable.
That being said, they do advise that you never plug or unplug the joystick while the system is on. Even if the autofire feature works on newer joysticks, they also advise against using it here. Given that this is an open-source solution, modifications are encouraged and should be shared!