14. Framebuffer support

barebox has support for framebuffer devices. Currently there is no console support for framebuffers, so framebuffer usage is limited to splash screens only. barebox supports BMP and PNG graphics using the splash (display a BMP or PNG splash image) command. barebox currently has no support for backlights, so unless there is a board specific enable hook for enabling a display it must be done manually with a script. Since barebox has nothing useful to show on the framebuffer it doesn’t enable it during startup. A framebuffer can be enabled with the enable parameter of the framebuffer device:

fb0.enable=1

Some framebuffer devices support different resolutions. These can be configured with the mode_name parameter. See a list of supported modes using devinfo fb0. A mode can only be changed when the framebuffer is disabled.

A typical script to enable the framebuffer could look like this:

#!/bin/sh

SPLASH=/path/to/mysplash.png

if [ ! -f $SPLASH ]; then
    exit 0
fi

# first show splash
splash /path/to/mysplash.png

# enable framebuffer
fb0.enable=1

# wait for signals to become stable
msleep 100

# finally enable backlight
gpio_direction_output 42 1