resolution changes after shutdown, restores on reboot

I am presenting a class to 15 high school students at a small disadvantaged high school. They are going to assemble their raspberry pi 3 computer and do some basic system admin tasks. If they want, they can take the finished system home. I love deitpi.

To avoid the time it requires to download all of the application software, I am cloning all of the 32GB micro SD cards with a particular setup. The system starts in LXDE desktop.

I am sure my problem is simple. The system uses an HDMI to VGA adapter and a Dell monitor. In /DeitPi/config.txt, I edited the file so HDMI hotplug is enabled and boost is 5. Other display settings were made through dietpi-launcher (display, GPU split = desktop, etc.).

After a shutdown, the display boots in poor resolution. sudo reboot makes the resolution settings correct. The screen size and font size stays the same in both cases. After the shutdown, the display, including text and images, is fuzzy or unreadable. My assumption is somehow the settings are not correct after a shutdown, but I am not sure where to make the change.

My work around is to open an lxterminal and type sudo reboot.

Any help would be appreciated.


I figured it out.

I ran these two commands:

/opt/vc/bin/tvservice -d edid.dat
/opt/vc/bin/edidparser edid.dat

buried deep is a line that says … best score mode is now DMT (35) 1280x1024 @ 60Hz

Edit the config
nano /DietPi/config.txt

and change the appropriate lines to be:

# hdmi_safe=1

# hdmi_group=2 sets to DMT

# hdmi_mode=35 sets display to 1280x1024 @60Hz

# hdmi_drive=2 sets to normal HDMI with sound

# config_hdmi_boost=5 boosts signal can go as high as 9

This site helped me figure it out: