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Fix Config.txt

There is a strange bug where the line in this file cannot go beyond a certain length. I have to manually break all parameters into separate line.

/boot/config.txt

dtoverlay=ads7846
dtparam=cs=1,penirq=17,penirq_pull=2,speed=1000000,swapxy=1,pmax=255
dtparam=xohms=60,xmin=200,xmax=3900,ymin=200,ymax=3900

Test Transformation

The touch screen for y axis is swapped. Reading from raspberry forum, the configuration is changed from evdev to libinput.

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

Make Permanent

/etc/X11/xorg.conf.d/99-calibration.conf

Option "TransformationMatrix" "-1 0 1 0 1 0 0 0 1"

References

https://wiki.ubuntu.com/X/InputCoordinateTransformation waveshare wiki http://www.circuitbasics.com/raspberry-pi-touchscreen-calibration-screen-rotation/

A single pixel