I have setup x11vnc on the RockPi4B (debian), without any monitor connected.
The screen resolution is very small 800x480 pixel. 
xrandr shows:
Screen 0: minimum 320 x 200, current 800 x 480, maximum 8192 x 8192
HDMI-1 disconnected primary (normal left inverted right x axis y axis)
DSI-1 connected 800x480+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
800x480 61.88
“cat /sys/class/drm/card0-HDMI-A-1/modes” is empty
How can I acitavte HDMI and/or set the resolution?
Because there is no HDMI, the resolution by default is MIPI, the Raspberry Pi display…
You can try to set the resolution with following command:
xrandr --output HDMI-1 --mode 1920x1080 --refresh 60
Hi Jack,
doing this brings the following error message: “xrandr: cannot find mode 1920x1080”
I tried the following flow:
cvt 1024 768 60
Modeline “1024x768_60.00” 63.50 1024 1072 1176 1328 768 771 775 798 -hsync +vsync
sudo xrandr --newmode “1024x768_60.00” 63.50 1024 1072 1176 1328 768 771 775 798 -hsync +vsync
sudo xrandr --addmode DSI-1 “1024x768_60.00”
sudo xrandr --output DSI-1 --mode “1024x768_60.00”
However,from the raspberry Pi I know this needs to be adjusted in /boot/config.txt. However there is no config.txt in the RockPi Debian.
Hello mgarza, I have exactly the same problem. Could you find out where to place a script to generate the new mode and start it when booting? Did the radxa team help?
Hello you can use the environment variable DISPLAY to selected the HDMI display, on your HDMI console type xhost + to access connect from other host and type echo $DISPLAY to show your HDMI display value. On other host like x11vnc type DISPLAY='HDMI display value',and then you can sue xrandr command to change HDMI resolution.
Hi could you please be more explicit?
xrandr says:
pi@rockpi-4b:~$ xrandr -q
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
HDMI-1 disconnected primary (normal left inverted right x axis y axis)
pi@rockpi-4b:~$ xrandr --verbose
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
HDMI-1 disconnected primary (normal left inverted right x axis y axis)
Identifier: 0x41
Timestamp: 30212
Subpixel: unknown
Clones:
CRTCs: 0 1
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
max bpc: 0
range: (8, 16)
link-status: Good
supported: Good, Bad
CONNECTOR_ID: 49
supported: 49
non-desktop: 0
range: (0, 1)
pi@rockpi-4b:~$
echo $DISPLAY
:0.0
pi@rockpi-4b:~$ xrandr --addmode HDMI-1 1920x1080_60
xrandr: cannot find mode “1920x1080_60”
I don’t understand how translate your answer into shell commands.
Please help