I wrote some digital input to USB HID support software using a $6 microcontroller

I made a fun, simply, working, weekend project:

https://gitlab.com/SpringCitySolutionsLLC/usb-hid-circuitpython-rp2040

Given a video game like DCS World or Elite Dangerous, it's fun to make a "real world" control panel with real world switches hooked up to the game, and people have been doing this for many years with "hundred dollar" digital input to USB adapter / appliances.

However, technology has improved over the years, and now for only $6, anyone can buy a Raspberry Pi RP2040 microcontroller running "CircuitPython" which is a limited Python language wedged into a microcontroller under a MIT free software license.  I decided to use the same MIT software license for my software linked above, please use it and have fun!  The RP2040 supports custom USB HIDs so I can easily emulate a multi-button joystick in software, and the buttons of this emulated joystick can then follow the switch inputs of the microcontroller's GPIO ports.

The hardware costs of the entire project are $6 for the microcontroller (plus a USB cable, I guess) and the software costs of the entire project, including the software I wrote, are zero dollars completely open source software.

I think this was a relatively simple software task.  Surprisingly, there do not seem to be many competing examples of this kind of code.  I tried to write the code and docs as obvious and clear and simple as humanly possible, although USB HID is ... non trivial so there is some inherent and unavoidable complexity in even the most minimal system.  I believe most home hobbyist simulation panel constructors are much handier with a miter saw or drill press than with a fancy software engineering IDE, and I also think they have more experience flying real airplanes than writing avionics software, so I'm trying to respect the needs of my end users, by making the code as simple as possible.  Just read the source code top to bottom, there's nothing tricky about it.

The demonstration code I have simply connects three toggle switches to a virtual joystick's first three buttons.  Obviously this could be trivially extended to something with more switches like a 'Huey' UH1-H helicopter's C-1611 Signal Distribution Panel, so you could flip a switch and turn the in-game helicopter's various radios on and off, or any other control panel in the game, such as the engine fuel control panel, or the overhead panel with the cockpit light dimmer dials.  Or this could be applied to any other simulation-type game, perhaps control your landing gear in Elite-Dangerous.

CircuitPython provides a very enjoyable software development experience.  A bit smoother integration with VS Code or Sublime Text would be nice.