This article is a updated version of an earlier one, which describes how to tweak the R400 on non-systemd systems.

In 2002, I received a Logitech R400 presenter tool for Christmas as a replacement for the php|architect pointer that has now fallen apart. However, to use it together with my presentation system—pres2, about which I previously wrote—I need it to provide left and right arrow keypresses. By default its left and right buttons generate Prior and Next events in X. It took me a while to get this to work, so in short, this article sets out how I changed it.

First of all, I editted the file /lib/udev/hwdb.d/60-keyboard.hwdb as root. I searched for R400 and changed its entry to:

# Logitech Presenter R400
keyboard:usb:v046DpC52Dd*dc*dsc*dp*ic*isc*ip*in00*
 KEYBOARD_KEY_070029=f11
 KEYBOARD_KEY_07003e=f11
 KEYBOARD_KEY_070037=f5
 KEYBOARD_KEY_07004b=left
 KEYBOARD_KEY_07004e=right

This maps the two scan codes that the Play button (lower-left) generates to f11, the empty screen button to f5 and the left and right buttons to the left and right arrow keys.

The first column represents the scancode, which I obtained by first looking up with input event the device was tied to:

stat -t /dev/input/by-id/usb-Logitech_USB_Receiver-event-kbd --printf "%N\n"

Which showed the following for me:

‘/dev/input/by-id/usb-Logitech_USB_Receiver-event-kbd’ -> ‘../event19’

To find out the scan codes, I had to download a getscancodes tool, and then compile it:

wget 'http://downloads.sourceforge.net/project/keytouch/getscancodes/getscancodes%201.0/getscancodes-1.0.tar.gz?r=http%3A%2F%2Fkeytouch.sourceforge.net%2Fdl-getscancodes.php&ts=1412723944&use_mirror=kent' -O getscancodes-1.0.tar.gz
tar -xvzf getscancodes-1.0.tar.gz
cd getscancodes/
make

With the new binary, and the event19 from above, I ran:

sudo ./getscancodes /dev/input/event19

Which showed:

458807 (0x70037)
458793 (0x70029)
458814 (0x7003e)
458827 (0x7004b)
458830 (0x7004e)

With these numbers, I now had enough information to edit the /lib/udev/hwdb.d/60-keyboard.hwdb file that I mentioned earlier.

After that, I had to run:

sudo udevadm hwdb --update

This consolidated the modified rules and made the keymapping active. My presenter tool now sends the correct key codes again.

The changes will persist after rebooting as well.