Tweaking the Logitech R400 presenter tool on Linux

This article is outdated, please refer to a new version.

Updated on April 9th, 2013, after comments by Jim Diamond

For Christmas I received a Logitech R400 presenter tool as a replacement for the php|architect one 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 is how I changed it. First of all, I created the file /etc/udev/logitech-r400 as root with contents:

0x70037 f5
0x70029 f11
0x7003E f11
0x7004B left
0x7004E right

This maps the two scan codes that the Play button (lower-left) both 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’ -> ‘../event16’

Then with event16 I ran:

/lib/udev/keymap -i input/event16

And pressed all four buttons (and the Play button twice). This then showed up on the screen:

scan code: 0x7004B   key code: pageup
scan code: 0x7004E   key code: pagedown
scan code: 0x7003E   key code: f5
scan code: 0x70029   key code: esc
scan code: 0x70037   key code: dot

After creating the file, to test things I ran:

sudo /lib/udev/keymap input/event16 /etc/udev/logitech-r400

Which showed:

Remapped scancode 0x70037 to 0x3f (prior: 0x34)
Remapped scancode 0x70029 to 0x57 (prior: 0x01)
Remapped scancode 0x7003e to 0x57 (prior: 0x3f)
Remapped scancode 0x7004b to 0x69 (prior: 0x68)
Remapped scancode 0x7004e to 0x6a (prior: 0x6d)

After this ran, the presenter tool now sends the key presses that I want. To make this permanent, I added as root a new file /etc/udev/rules.d/logitech.rules, with as contents:

ENV{ID_VENDOR}=="Logitech*", ATTRS{idProduct}=="c52d", RUN+="keymap $name /etc/udev/logitech-r400"

The changes will now also persist after rebooting as well.

My first possibility to test the new tool will be at PHP Benelux where I will be giving a MongoDB tutorial on January 25th. Tickets are still available.