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I am trying to use a Logitech G400 Mouse on a PC with Ubuntu 14.04.

However, I can't make Ubuntu recognise two of its buttons (DPI+ and DPI-).

How can I make these buttons recognised?

Apparently, this question is related to a previous one but I could not find a solution there or anywhere else.

Details:

Logitech G400 Optical Gaming Mouse

$ uname -a
Linux 3.13.0-53-generic #89-Ubuntu SMP Wed May 20 10:34:39 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

$ lsb_release -a
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.2 LTS
Release:        14.04
Codename:       trusty

Results from xev:

  • Left-click : Button 1
  • Middle-click : Button 2
  • Right-click : Button 3
  • Wheel Up : Button 4
  • Wheel Down : Button 5
  • Thumb Forward: Button 8
  • Thumb Back : Button 9
  • Task Switcher : Button 10
  • DPI+ : no response from xev
  • DPI- : no response from xev
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  • There is no solution so far. Linux does not support proprietary mode for this mouse.
    – Pilot6
    Jun 2, 2015 at 8:35
  • I am using exactly this mouse on my Ubuntu 15.04 (and older versions before). Does the cursor speed change, after you change the dpi?
    – davidbaumann
    Jun 2, 2015 at 8:58
  • I use this mouse on my desktop with openSUSE and btnx. It recognizes all buttons and lets me configure them. I have not tried to compile btnx on Ubuntu (unfortunately it is not in the repos). However, it definitely is worth a try. though strangly enough the two buttons you mention work fine even without configuration on the openSUSE box...and I think they were also working on my Ubuntu 14.04 laptop (going to check this)
    – Bruni
    Jun 2, 2015 at 9:37
  • @davidbaumann: my problem is exactly that the DPI+ and DPI- are not recognised, so I can't change the dpi with them. You can use xinput instead to change the cursor speed.
    – toliveira
    Jun 3, 2015 at 11:13
  • @Bruni, thank you, I will try btnx. This mouse and all its buttons worked out of the box on my laptop, but not on my desktop. I can't find the difference between the two machines.
    – toliveira
    Jun 3, 2015 at 11:14

1 Answer 1

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I might have a solution...

I wrote a tool recently, https://github.com/rprichard/logitech-g400-config, that allows configuring both the polling rate (125 Hz -- 1000 Hz) and the DPI setting. (My motivation was to avoid horrific lag when moving windows, e.g. https://www.youtube.com/watch?v=mwBH_AkhW_Q.)

To develop the tool, I examined the USB traffic from the Windows Logitech software using Wireshark. I noticed the software using two HID "feature reports": one for the sampling rate and another for the DPI level. The DPI level report had ID 0x8e with a second byte of 3, 4, 5, or 6. I think they correspond to 400, 800, 1800, and 3600 DPI.

During development of this script, though, I noticed that the device is also happy with a DPI level of 7. It turns out that if I set the DPI to 7, then the DPI+/DPI- buttons no longer adjust the DPI and instead send an event visible with xev. The DPI-default button is always visible with xev.

I'm guessing that DPI-6 and DPI-7 are both 3600 DPI. (My other guess had been that DPI-7 would retain the pre-7 DPI (e.g. DPI-3 followed by DPI-7 would be 400 DPI), but that doesn't appear to be the case.)

To set DPI-7, just run logitech-g400-config.py set -d3600_frozen (after installing libhidapi and maybe setting up udev -- see the README for details). The high DPI might make the mouse pointer very fast. I'm personally using DPI-5 right now with a bunch of xinput settings to tweak the acceleration.

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