macropad-f13-mapping.md

Macropad Button to F13 Key Mapping

Problem

A macropad (HID 5131:2019) was sending KEY_2 (scancode 7001f) when a button was pressed, but needed to send F13 instead.

Solution

Use udev's hwdb (hardware database) to remap the scancode to F13.

Steps

1. Identify the device and scancode

   # Find your device
   cat /proc/bus/input/devices | grep -A 5 "5131:2019"
   
   # Monitor keypresses to get scancode
   sudo evtest /dev/input/eventX  # Replace X with your device event number

2. Create hwdb rule Create /etc/udev/hwdb.d/90-macropad.hwdb:

   # Remap macropad button 2 to F13
   # Device: HID 5131:2019
   evdev:input:b0003v5131p2019*
    KEYBOARD_KEY_7001f=f13
   

   Important: The line with KEYBOARD_KEY_7001f=f13 must start with a single space, not a tab.

3. Apply the changes

   # Copy the file to the correct location
   sudo cp 90-macropad.hwdb /etc/udev/hwdb.d/
   
   # Update the hardware database
   sudo systemd-hwdb update
   
   # Trigger udev to reload
   sudo udevadm trigger

4. Test

   • Unplug and replug the macropad, or reboot
   • Press the button - it should now send F13

hwdb Rule Format

evdev:input:b<bus_id>v<vendor_id>p<product_id>*
 KEYBOARD_KEY_<scancode>=<keyname>

• b0003 = USB bus (0003)
• v5131 = Vendor ID (5131)
• p2019 = Product ID (2019)
• 7001f = Scancode in hex
• f13 = Target key name (see /usr/include/linux/input-event-codes.h for all key names)

References

• systemd hwdb documentation
• Available key names: /usr/include/linux/input-event-codes.h
• Test with: evtest or xev (for X11)