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.
Turn off
Do echo none to turn off.
root@odroid:~# echo none > /sys/class/leds/blue\:heartbeat/trigger
Turn on
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
netdev trigger
netdev trigger will blink the blue led if there's network traffic.
- Requirement for N2: Ubuntu 18.04 kernel 4.9.230-76, Ubuntu 20.04 kernel 4.9.230-95
- Requirement for C4: Ubuntu 20.04 kernel 4.9.230-29
- Requirement for XU4: Kernel 5.4
Enable netdev trigger:
echo netdev > /sys/class/leds/blue\:heartbeat/trigger
Set the interface to be monitored:
echo eth0 > /sys/class/leds/blue\:heartbeat/device_name
Interval in mS for blinking, lower is faster blinking, higher is slower, minimum is around 40
echo 40 > /sys/class/leds/blue\:heartbeat/interval
Link: Should we monitor if the link is up or down? (Link = Physical cable).
1 we monitor link status, the led behaviour is: on when link is up, flashing when there's activity.
0 we don't monitor link status, the led behaviour is: always off, flashing when there's activity.
echo 0 > /sys/class/leds/blue\:heartbeat/link
RX/TX Blinking
Enable RX Blinking
echo 1 > /sys/class/leds/blue\:heartbeat/rx
Enable TX Blinking
echo 1 > /sys/class/leds/blue\:heartbeat/tx
- 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.
How to control the Red power LED (Applicable for the ODROID-HC4 only)
The Red LED on the HC4 board is not hard-wired and you can turn it off by software.
The GPIO number of the red LED on the HC4 board is 503.
# Export GPIO root@odroid:~# echo 503 > /sys/class/gpio/export # To set as Output root@odroid:~# echo out > /sys/class/gpio/gpio503/direction # Output as low. root@odroid:~# echo 0 > /sys/class/gpio/gpio503/value