force resolution HDMI, much variants unfortunately does not works

[epi kao]

Hello all

I have a TFT with 1920x720, and I try to control this with the HDMI from my BBB.

I am trying with cmdline

cmdline=coherent_pool=1M quiet cape_universal=enable video=HDMI-A-1:1920x720M@30e

this disable the hdmi-output

but i think the output is randomly... actually the resolution is 640x480, it seems that my BBB takes the resolution from previous adjustment in the uEnv.txt. But now the resolution that i have adjust is 800x480... and it takes 640?? why

anyway how can I know which resolution works surely?

thanks

[epi kao]

i am also trying this, but always "no protocol specified" ..... i am frustated :-( ..

root@beaglebone:/# export XAUTHORITY='ls /var/run/gdm/auth-for-root-*/database'

root@beaglebone:/# export DISPLAY=:0.0

root@beaglebone:/# xrandr --ouptut HDMI-0 --mode 720x480 --rate 60

xrandr: unrecognized option '--ouptut'

Try 'xrandr --help' for more information.

root@beaglebone:/# xrandr --output HDMI-0 --mode 720x480 --rate 60

No protocol specified

Can't open display :0.0

root@beaglebone:/# export DISPLAY=:'0.0'

root@beaglebone:/# xrandr --output HDMI-0 --mode 720x480 --rate 60

No protocol specified

Can't open display :0.0

root@beaglebone:/# xrandr --output HDMI-0 --mode 1280x800 --rate 60

No protocol specified

Can't open display :0.0

[epi kao]

with raspberry it's really much simpler!! :-(

=> I was successfully set up the output by simply adding a command"hdmi_cvt=1920 720 60 0 0 0 0" in config.txt