question

Try running ts_calibrate. It's not installed by default but MIGHT be available via:

opkg install tslib-calibrate 

On further thought, the local GUI needs to be disabled to run ts_calibrate and not sure you can do that on Cerbo.

Many thanks for the hint using ts_calibrate.

Following this German HowTo for Venus on a RaspberryPI here are the necessary steps:

1. Update the firmware of the CerboGX

2. make root access and ssh to the CerboGX available. Attention: Don't use special characters in the root password on the remote console (don't know why)

3. login via ssh as root@ip_of_your_CerboGX

4. type the following commands:

opkg update
opkg install tslib-calibrate tslib-conf tslib-uinput tslib-tests 
opkg install qt4-embedded-plugin-mousedriver-tslib

5. set some environment variables by typing the following commands:

TSLIB_FBDEVICE=/dev/fb0
TSLIB_TSDEVICE=/dev/input/touchscreen0
TSLIB_CALIBFILE=/etc/pointercal
TSLIB_CONFFILE=/etc/ts.conf
TSLIB_PLUGINDIR=/usr/lib/ts
touch /etc/venus/headless

The last line ensures that the system boots "headless", so don't expect any output on the display after next reboot!

6. Do a reboot

reboot

7. After 2..3 minutes log in via ssh and type

ts_calibrate

the display resolution should be appearing in the ssh session.

On the display you see a crosshair mark at the left upper side. Touch it precisely, then the mark appears at the right upper side, then left down, right down and at the last in the middle.

8. After that procedure disable the headless by typing

mv /etc/venus/headless /etc/venus/headless.off

9. Edit the GUI startup file using the following command (or use vi ;-) ):

nano /opt/victronenergy/gui/start-gui.sh

insert the following lines in the shell file after the last comment line in the #when headfull section:

export TSLIB_TSEVENTTYPE=INPUT
export TSLIB_CONSOLEDEVICE=none
export TSLIB_FBDEVICE=/dev/fb0
export TSLIB_TSDEVICE=/dev/input/touchscreen0
export TSLIB_CALIBFILE=/etc/pointercal
export TSLIB_CONFFILE=/etc/ts.conf
export TSLIB_PLUGINDIR=/usr/lib/ts
export QWS_MOUSE_PROTO=tslib:/dev/input/touchscree0

Type <ctrl><x> and save the modifications.

10. reboot again and the display should work with correct touch resolution.

11. disable automatic firmware updates on the CerboGX using the touch display or remote console, that might be destroy the work done yet.

12. log in again as root using ssh and type the following:

cd /data
nano rc.local

paste the following lines in that file

!/bin/bash
if diff /data/start-gui.sh /opt/victronenergy/gui/start-gui.sh >/dev/null;
then
echo „no software update detected, exiting“
else
opkg update
opkg install qt4-embedded-plugin-mousedriver-tslib
opkg install tslib-calibrate
opkg install tslib-conf
opkg install tslib-tests
TSLIB_PLUGINDIR=/usr/lib/ts ts_calibrate
rm /opt/victronenergy/gui/start-gui.sh
cp /data/start-gui.sh /opt/victronenergy/gui/start-gui.sh
mv /etc/venus/headless /etc/venus/headless.off
cp /data/backlight_device /etc/venus/backlight_device
cp /data/blank_display_device /etc/venus/blank_display_device
rm /etc/pointercal
cp /data/pointercal /etc/pointercal
reboot
fi

save using <CTRL><X>.

13. Now type the following lines:

cp /opt/victronenergy/gui/start-gui.sh /data/start-gui.sh
cp /etc/venus/backlight_device /data/backlight_device
cp /etc/venus/blank_display_device /data/blank_display_device
cp /etc/pointercal /data/pointercal

After that all these copied files should appear in the /data directory. You can see this by

ls /data

14. the next step is setting the right permissions

chmod 755 rc.local

15. Last step is rebooting the CerboGX

reboot

Conclusion: The solution saves you around 200 € but it consumes one full-functional USB port of the CerboGX.