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How to Control Blue Status LED

We can control the blue LED with editing the trigger mode in sysfs.

The red LED is hard-wired to the power input rail so that cannot be changed.

Simply you can turn on/off that with putting an option using echo command.

Do echo none to turn off.

root@odroid:~# echo none > /sys/class/leds/blue\:heartbeat/trigger

Do echo MODE to turn on with MODE.

# Turn on that solidly.
root@odroid:~# echo default-on > /sys/class/leds/blue\:heartbeat/trigger
 
# Heartbeat mode. This is the original state.
root@odroid:~# echo heartbeat > /sys/class/leds/blue\:heartbeat/trigger

There are many other modes you can select. But some of them may now work. This is an example for N2.

root@odroid:~# cat /sys/class/leds/blue\:heartbeat/trigger
none kbd-scrolllock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock kbd-ctrlllock kbd-ctrlrlock timer oneshot [heartbeat] backlight gpio cpu0 cpu1 cpu2 cpu3 cpu4 cpu5 default-on transient panic rc_feedback emmc sd
  • If you want to turn the LED off automatically in boot process, add echo none > /sys/class/leds/blue\:heartbeat/trigger in /etc/rc.local file.