A tool for filtering mechanical keyboard chattering on Linux

Switches on mechanical keyboards occasionally start to "chatter", meaning when you press a key with a faulty switch it erroneously detects two or even more key presses.

Apart from buying a new keyboard, there have been ways to deal with this problem using software methods. The idea is to filter key presses that occur faster than a certain threshold. "Keyboard Chattering Fix v 0.0.1" is a tool I had been using on Windows for a long time, and these days you also have Keyboard Chatter Blocker, which is a nice open source tool with some additional functionality. It's actually what I use myself when I use Windows.

Unfortunately, all existing tools only work on Windows. On Linux, the answer everyone seems to give is to use the Bounce Keys feature of X, but it's not really useful in this way. For one, it resets the delay even on filtered key presses, meaning that if you press the key fast enough, none of the presses with pass through, ever. And if the key chatters, this is bound to happen eventually and interfere with fast repeated key presses.

This tool attempts to solve any such problems that may arise by having full low-level access and control over all keyboard events. Using libevdev's Python bindings, it grabs your keyboard's event device and processes its events, then outputs the result back to the system using /dev/uinput, effectively emulating a keyboard - one that doesn't chatter, unlike your real one!

This also means it works across the system, without depending on X.

As for the filtering rule, what seems to work well is the time between the last key up event and the current key down event. When the key chatters, that time seems to be very low - around 10 ms. By filtering such anomalies, we can hopefully remove chatter without impeding actual fast key presses.

Clone the repository and install the required dependencies enlisted in requirements.txt.

sudo <path-to-python-executable> -m src

• -k KEYBOARD, --keyboard KEYBOARD

  • Name of your chattering keyboard device as listed in /dev/input/by-id. If left unset, will be attempted to be retrieved automatically. The device is captured by-id, and therefore in a persistent way.

• -t THRESHOLD, --threshold THRESHOLD

  • Filter time threshold in milliseconds. Default=30ms. Note: This does not denote the time between key presses, but between a key being released and pressed again, so the number should probably be lower than you might think. For reference, if you press the key really fast this delay is around 50 ms.

• -v {0,1,2}, --verbosity {0,1,2}

Starting the script manually every time doesn't sound like the greatest idea, so you should probably consider something that does it for you. The solution I provide is a systemd unit file. Copy it to /etc/systemd/system/, then enable it with systemctl enable --now chattering_fix. Don't forget to change the command inside to tell the service what id your keyboard has and where the script is located. The script should be executable as well.