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Touchscreen issues

Contents:

Beware that this document focuses on RaspberryOS but most of it should apply to any other Debian based distros

Touch not working

If the screen is connected over USB, the cable may cause issues. For that, please see this guide.

DSI screens touch not working on RaspberryOS / MainsailOS version Debian 11 Bullseye

Some DSI screens have issues where touch doesn't work with the default configuration. The current workaround/temporary fix involves changing the kernel driver module used for these displays.

sudo nano /boot/config.txt and change

dtoverlay=vc4-kms-v3d

to

dtoverlay=vc4-fkms-v3d

Close the nano editor using ctrl+x (exit), then y for yes (save).

Reboot to apply changes. sudo reboot

If that doesn't fix it, you can try commenting these lines out, resulting in:

# dtoverlay=vc4-kms-v3d
# max_framebuffers=2

Reboot to apply changes. sudo reboot

Touch rotation and matrix

If the touch works but registers touch input in a different location from the input, then you may need to apply an input transformation matrix.

First you will need your device name. On a terminal, run:

DISPLAY=:0 xinput
Alternative 
libinput list-devices

Note

requires libinput-tools 

sudo apt install libinput-tools

Output:

⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ ADS7846 Touchscreen                       id=6    [slave  pointer  (2)]
⎣ Virtual core keyboard                         id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]

In this case the device is the ADS7846 Touchscreen, yours may be different

You can test a change by running:

DISPLAY=:0 xinput set-prop "<device name>" 'Coordinate Transformation Matrix' <matrix>

Example

DISPLAY=:0 xinput set-prop "ADS7846 Touchscreen" 'Coordinate Transformation Matrix' -1 0 1 0 -1 1 0 0 1

Where the matrix can be one of the following options:

Rotation Matrix
0° 1 0 0 0 1 0 0 0 1
90° Clockwise 0 -1 1 1 0 0 0 0 1
90° Counter-Clockwise 0 1 0 -1 0 1 0 0 1
180° (Inverts X and Y) -1 0 1 0 -1 1 0 0 1
invert Y -1 0 1 1 1 0 0 0 1
invert X -1 0 1 0 1 0 0 0 1
expand to twice the size horizontally 0.5 0 0 0 1 0 0 0 1

To make the calibration permanent read Save touch calibration

Touch calibration

This is optional, and you should only do it if you are having problems.

Download and build xtcal:

sudo apt-get install libxaw7-dev libxxf86vm-dev libxft-dev
cd
git clone https://github.com/KurtJacobson/xtcal
cd xtcal
make
cd ..

First you will need your touchscreen device name. On a terminal, run:

DISPLAY=:0 xinput
Alternative 
libinput list-devices

Note

requires libinput-tools 

sudo apt install libinput-tools

Output:

⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ ADS7846 Touchscreen                       id=6    [slave  pointer  (2)]
⎣ Virtual core keyboard                         id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]

In this case the device is the ADS7846 Touchscreen, yours may be different

Reset the old calibration: (set the 0° roation matrix: 1 0 0 0 1 0 0 0 1) 

DISPLAY=:0 xinput set-prop "ADS7846 Touchscreen" 'Coordinate Transformation Matrix' 1 0 0 0 1 0 0 0 1
Run the calibrator - if it's not fullscreen cancel with ctrl+c and adjust geometry 
DISPLAY=:0 xtcal/xtcal -geometry 480x320

Important

KlipperScreen or a desktop environment should be on the screen to launch the calibrator

Touch the center of the crosses in order, they should turn white.

xtcal_preview

Test the calibration

Copy the output of the calibration and test it, For example: 

DISPLAY=:0 xinput set-prop "ADS7846 Touchscreen" 'Coordinate Transformation Matrix' -0.016267 -0.952804 0.978336 -1.010164 0.065333 0.998316 0 0 1
if it's not correct reset the matrix and run xtcal again.

Save touch calibration

modify /etc/udev/rules.d/51-touchscreen.rules:

sudo nano /etc/udev/rules.d/51-touchscreen.rules
51-touchscreen.rules
ACTION=="add", ATTRS{name}=="<device name>", ENV{LIBINPUT_CALIBRATION_MATRIX}="<matrix>"

Close the nano editor using ctrl+x (exit), then y for yes (save).

sudo reboot

Example

sudo nano /etc/udev/rules.d/51-touchscreen.rules
51-touchscreen.rules
ACTION=="add", ATTRS{name}=="ADS7846 Touchscreen", ENV{LIBINPUT_CALIBRATION_MATRIX}="-1 0 1 0 -1 1 0 0 1"

Close the nano editor using ctrl+x (exit), then y for yes (save). 

sudo reboot

Alternative Example

As an alternative if the above doesn't work:

determine the touchscreen driver (usually libinput):

cat /var/log/Xorg.0.log
example of /var/log/Xorg.0.log
...
(II) Using input driver 'libinput' for 'ADS7846 Touchscreen'
...

if it says evdev instead, then change libinput to evdev below, both in the filename and in the file

sudo nano /usr/share/X11/xorg.conf.d/40-libinput.conf
40-libinput.conf
Section "InputClass"
        Identifier "libinput touchscreen catchall"
        MatchIsTouchscreen "on"
        MatchDevicePath "/dev/input/event*"
        Driver "libinput"
        Option "TransformationMatrix" "0 -1 1 1 0 0 0 0 1"
EndSection

Note

the number of the filename determines the order of loading, if you have issues check if there are other files overriding your config or just use 99-touch_calibration.conf as a name.

Close the nano editor using ctrl+x (exit), then y for yes (save). 

sudo reboot

For more in-depth guidance on using Coordinate Transformation Matrices: