Howto: disable HDMI blanking in Ångström on BeagleBone Black (BBB)
Jul 9th, 2014 by miki

A very annoying feature of the Ångström image that is shipped with the BeagleBone Black, is that a display connected to the HDMI output of the board will by default be blanked when powering up, and is first woken when any pointer activity occur (touch/mouse).

This seems to originate from the fbdev that is used for displaying graphics, and it took me some time to figure out how to cirumvent it. The normal X commands for controlling blanking of “xset -dpms” or “xset s off” did nothing, and neither did the terminal options of “setterm powersave off” or “setterm powerdown 0”. I went all the way back to old ANSI escape sequences trying “echo -e ‘\033[9;X]'” without success.

Luckily I fell by at’s framebuffer tips, which listed the sys-fs node named /sys/class/graphics/fb0/blank that controls blanking of the low level framebuffer, thus executing (as root)

echo 0 > /sys/class/graphics/fb0/blank

disables blanking and wakes up the BBB HDMI output.

To do this at every boot (really login) you can use the Gnome Startup Applications Preferences (gnome-session-properties) to execute this at Gnome autologin, or add it to whatever startup script you see fit.

Beware that you might need to delay the execution when using the gnome-session-properties, I had to put in  a sleep, but that probably depends on what other stuff is starting up from it.



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