I am using the latest MachineKit (downloaded from http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#BBW.2FBBB_.28All_Revs.29_Machinekit) image and am trying to change the hdmi resolution to use it with a generic 5 inch lcd screen. The resolution I require is 800x480.
What I have tried:
- xrandr: I tried following the instructions on the main beaglebone page (http://elinux.org/Beagleboard:BeagleBoneBlack_HDMI#Forcing_A_Resolution)
Type export XAUTHORITY=
ls /var/run/gdm/auth-for-root-*/database and hit enter.
Type export DISPLAY=:0.0 and hit enter.
Type xrandr --output HDMI-0 --mode 800x480 --rate 60. You can substitute different resolutions and refresh rates if you like. Hit enter.
This method gives an error “No protocol specified. Can’t open display :0.0”
I have tried other lcd names such as “default” and “HDMI-0”
- modifying uEnv.txt: I tried adding “kms_force_mode=video=HDMI-A-1:800x480M@60” to the uEnv.txt file (in both /boot and /media/machinekit/boot) as suggested at http://blog.machinekit.io/2013/07/custom-hdmi-resolution.html. I tried changing the name of the screen from “HDMI-A-1” to “HDMI-0” and “default”.
This gives no errors, but also seems to have no effect on the resolution.
I am doing this on a tv screen which may not support the resolution I am trying to change it to. This is because I cannot see enough of the screen on the lcd at the wrong resolution to open the terminal and modify things- could this be causing a problem? Should I be changing the settings via putty instead?
Thank you in advance,