wiki/ODROID-U3.md

HDMI audio

To enable audio over HDMI, add the following to your asound.conf:

pcm.!default {
   type hw
   card 0
}
ctl.!default {
   type hw
   card 0
}

LEDs

ODROIDs have dual LEDs: a red power LED which is always on if power is supplied, and a blue LED which can be configured.

By default, the blue LED is a heartbeat LED, which flashes when the kernel is running. This can be configured in /sys/class/leds/led1/trigger.

To list available triggers:

# cat /sys/class/leds/blue:heartbeat/trigger

Replace TRIGGER with one of the available triggers. This setting will apply instantly, but be lost upon reboot.

# echo TRIGGER > /sys/class/leds/blue:heartbeat/trigger

To create a persistent configuration, edit or create /etc/tmpfiles.d/leds.conf:

w /sys/class/leds/blue:heartbeat/trigger - - - - TRIGGER