The Endaptor (Enjoyance Adapter) is a work in progress adapter that lets you plug USB controllers and other devices into your Atari 2600. It uses a custom PCB with a PIC24FJ32GU202 microcontroller, enclosed in a 3D-printed case.
I learned more than I wanted to about USB controllers on this project. Did you know that there's a USB specification for human interface devices including gamepads, and that the majority of gamepads you can buy ignore it and implement a proprietary protocol? And that the only way to tell which protocol a controller uses is to just have a big list of products with the protocols they implement? And that products that implement the "same" protocol actually have subtle differences? This problem seems to be specific to gamepads: Keyboards, mice, storage devices, and audio/video devices pretty much all implement standard USB protocols. I guess we should blame Microsoft for being the first to use USB for their consoles and ignoring the spec.
The project is currently on hold as it was taking too much of my time. It works great with many controllers, but has a flaw that I would need to address before selling it: It is powered entirely by the console, and makes no attempt to limit current drawn from the peripheral. The minimum current a USB host needs to be able to provide is 500 mA. This is 100% of the current the Atari 2600's stock power supply is rated for, and the console itself draws current too, so peripherals that draw too much current can cause brownout. The console's voltage regulator is rated for 1A, so in theory the device could be made to work by replacing the power supply and adding current-limiting hardware to the adapter (so that misbehaving peripherals don't damage the console). Alternatively, it could just use a separate power source, though my retro gaming setup has enough wires as it is.
