I have a Raspberry 4 / 4G running Ubuntu, it has a 7” touch Screen connected with a ribbon cable. When Plug a TV or other Monitor into the HDMI port I only get sound. As soon get no options in the settings for the second monitor.
This what I get when I run xrandr with the second monitor plunged in
ubuntu@brad-pi:~$ xrandr xrandr: Failed to get size of gamma for output default Screen 0: minimum 800 x 480, current 800 x 480, maximum 800 x 480 default connected primary 800x480+0+0 0mm x 0mm 800x480 0.00* any help or point in the right direction would appreciated
11 Answer
I have the same configuration as you. (Ubuntu on a raspberry pi with 7" display with a second monitor connected via HDMI cable). The following worked for me.
sudo nano /boot/fireware/usercfg.txt After the file is open
# Definitely required dtoverlay=vc4-fkms-v3d # If one of the monitors have dark border disable_overscan=1 # Not sure what it does. Might not be required. max_framebuffers=2 Save and exit. Install the following
sudo apt install xfce4-settings Reboot
sudo reboot After login to check the displays
xfce4-display-settings & For me, this was displaying two monitors side by side (one huge and another small). To get the name of the displays:
xrandr --current If it is displaying two different monitors
xrandr --output <projector> --same-as <desktop> where in my case was HDMI-1 and was DSI-1. To switch off the (DSI-1) monitor
xrandr --output HDMI-1 && xrandr --output DSI-1 --off This will switch off the DSI-1 monitor.
