Taming the Logitech K380 Fn Key on Linux: A DIY Solution Link to heading

Introduction Link to heading

The Logitech K380 is a popular choice for its portability and multi-device compatibility. However, many Linux users find the default Fn key behavior frustrating. This post will guide you through creating a simple Bash script to toggle the Fn key on and off, providing you with greater control over your keyboard.

Understanding the Problem Link to heading

The Logitech K380, like many modern keyboards, employs a dual-function key layout where the standard F1-F12 keys are combined with media controls, accessible by pressing the Fn key. While this is convenient in some scenarios, it can be annoying for tasks requiring frequent use of the function keys.

The Solution: A Bash Script Link to heading

The following Bash script leverages the hidraw interface to communicate directly with the K380 and toggle the Fn key state.

#!/bin/bash

DEV="$(ls /sys/class/hidraw/ -l | grep 046D:B342 | grep -o 'hidraw[0-9]*$')"

if test -n "$DEV" ; then
  echo "K380 keyboard found. "
  if [ "$1" = "on" ]; then
    echo -ne "\x10\xff\x0b\x1e\x00\x00\x00" | sudo tee "/dev/$DEV"
    echo "Fn keys turned on."
  elif [ "$1" = "off" ]; then
    echo -ne "\x10\xff\x0b\x1e\x01\x00\x00" | sudo tee "/dev/$DEV"
    echo "Fn keys turned off."
  else
    echo "Missing operation. Expected 'on' or 'off' as argument"
    exit 1
  fi
else
  echo "Unable to find K380. Please check if attached or turned on."
fi

How the Script Works Link to heading

  1. Identifies the keyboard: The script searches for the K380 by looking for its vendor and product ID (046D:B342) in the hidraw directory.
  2. Sends commands: If the keyboard is found, the script takes an argument (on or off) and sends the corresponding byte sequence to the keyboard’s device file (/dev/$DEV) to toggle the Fn key state.
  3. Error handling: If the script fails to find the keyboard or receives an invalid argument, it provides informative error messages.

Using the Script Link to heading

  1. Save the script: Create a new file (e.g., k380_fn.sh) and paste the code into it.
  2. Make it executable: Run chmod +x k380_fn.sh in the terminal.
  3. Toggle Fn keys: To turn on the Fn keys, run sudo ./k380_fn.sh on. To turn them off, run sudo ./k380_fn.sh off.

Important Notes Link to heading

  • sudo: The script requires sudo privileges to access the hidraw device.
  • Keyboard identification: The script relies on the specific vendor and product ID of the K380. If you have a different keyboard, you’ll need to adjust the script accordingly.
  • Byte sequences: The byte sequences used to toggle the Fn key are specific to the K380 and might not work with other keyboards.
  • Testing: It’s recommended to test the script thoroughly before relying on it heavily.

Additional Considerations Link to heading

  • Keybindings: Consider using a keybinding tool like xbindkeys to create shortcuts for toggling the Fn key.
  • Desktop environments: Some desktop environments might offer built-in options for managing keyboard behavior.
  • Alternative methods: Explore other tools or software that might provide similar functionality.

By following these steps and understanding the script’s mechanics, you can effectively manage the Fn key behavior of your Logitech K380 on Linux.