No pressure on Monoprice (UC-Logic) drawing tablet in Linux (Ubuntu 16.10/Kernel 4.8)
There’s been a change in the evdev driver for xorg in the latest ubuntu update that seems to stop monoprice tablets from working correctly.
The effect is that the tablet appears to be working as far as clicking goes but all pressure sensitivity no longer functions. Taps with the pen seem to work fine.. it clicks as it were but can’t draw in krita at all.
After a fair bit of testing with different computers, distros, I came across this incredibly useful guide from the excellent DIGImend project on troubleshooting input issues.
I was getting the pressure reports all the way up until xinput where the pressure value just disappeared. It turns out that it’s a known issue in xserver-xorg-input-evdev as reported here.
So following a suggestion from the poster of the bug report I decided to try downgrading evdev to the previously working version and that seems to bring back the pressure sensitivity.
To remove the current (buggy) version of evdev used synaptic but you could just as easily use apt: sudo apt-get remove xserver-xorg-input-evdev
Getting the older version of evdev is a little more complicated, since it’s not a current version any more it’s no longer held in the current (yakkety) repo so it needs to be downloaded as a .deb package from http://packages.ubuntu.com/xenial/xserver-xorg-input-evdev .
Just download the file you need for the architecture (uname -m to check) that you’re running. In my case (x86_64) I needed the amd64 build so got that.
To install we need to use dpkg via this command: sudo dpkg -i xserver-xorg-input-evdev_2.10.1-1ubuntu2_amd64.deb change the filename to whatever your download is. Hopefully after restarting pressure sensitivity should be working again.
Finally, to stop the system updating to the newer version we need to lock the package. To do this I used Synaptic, find and highlight xserver-xorg-input-evdev and use the [Package] menu to [Lock Version].
Hopefully this might help someone else facing the this issue.
