This program uses a linux machine A to translate keypresses of physically connected keyboards to virtual USB joysticks that appear to a USB host connected to A's device-capable USB port.
flowchart LR
A1(USB Keyboard 0) -->|libevdev| B(keystick)
A2(USB Keyboard ...) -->|libevdev| B(keystick)
A3(USB Keyboard N) -->|libevdev| B(keystick)
B -->|libusbgx| C(USB gadget)
C -->|upstream-facing USB port| D(Windows machine)
This program is intended to run on a raspberry pi (tested on both pi4 and pi5). Connect as many keyboards as you need, then power up the pi and let keystick.service start the keystick binary. The program will then use libevdev to enumerate attached keyboards and use libusbgx to create a virtual joystick for each using the linux USB Gagdet API.
I like playing Atomic Bomberman. Unfortunately, it only supports 2 players using keyboards, while the remaining players have to use joysticks. Usually, there are way more keyboards than joysticks around, and even if not, using joysticks for Bomberman sucks.
- install raspberrypios on your rpi4
apt install build-essential git cmake libusbgx-dev libevdev-dev libconfig-dev libfmt-devcd && git clone https://github.com/benadler/keystickpushd keystick && mkdir build && pushd build && cmake .. && make install -j4 && popd && popdsudo cp keystick.service /etc/systemd/system && systemctl enable keystick
Connect all keyboards and then power up the pi; keystick can't deal with keyboards (dis)connecting during runtime, they all have to be static after startup.
Each joystick has 2 axes which are controlled by a keyboard's arrow keys and 8 buttons controlled using - in order - F, D, S, A, V, C, X, Z keys. If you want to change that, modify devicehid.cpp to advertise more/less axes/buttons and keyboardjoystick.cpp to report the key-changes properly.
- https://github.com/milador/RaspberryPi-Joystick emulates just one joystick (I think?) and its keys tended to get stuck sometimes. Since I can't write a line of python I didn't investigate further.
- https://sourceforge.net/projects/vjoystick/, PPJoy, KeyboardSplitterXbox and friends didn't work for me. Most were a bit older, needed installation of unsigned drivers and whatnot. Not saying they don't work, I might have done insufficient homework.
- https://www.rewasd.com is commercial. Haven't checked if it supports translating multiple physical keyboards to multiple virtual joysticks.
- Since a raspberry pi 4 is powered through the same USB port that's connected to the upstream machine, that'll have to supply enough current. I haven't run into issues, but maybe something like https://www.elmorlabs.com/product/usb-c-power-data-switch-for-raspberry-pi-4/ could be required.
I don't know what's appropriate. This is just glue code between libevdev (MIT?) and libusbgx (LGPL and GPL). So, maybe LGPL.