Table of Contents

Intro

Radxa Rock 5C has quite a few LEDs onboard. One for power, one for heartbeat, and one for EMMC activity. They are bright enough to illuminate my room at night. And annoy me the heck of me in case of blinking blue one. I need to find out how to drop its brightness. Preferably to zero.

Radxa's own Wiki

I was unable to find any wiki articles depicting LEDs on Rock 5C exactly. The only article that I found was this article on Radxa Wiki called "The Radxa Rock has 3 LEDs on board", so I presume it may fit all Rock series boards. Ok. Let's check.
Indeed, at the end of article section about turning LEDs off can be found. It suggests next commands:

echo none > /sys/class/leds/blue/trigger
echo none > /sys/class/leds/green/trigger
echo 0 > /sys/class/leds/red/brightness

One problem though. red, green and blue is absent from my system. Wiki may be outdated or tailored to Radxas own flavor of Linux. Or both. Anyway... I have Armbian installed and looks like have to figure this out by myself.

Finding correct names

Listing of contents of /sys/class/leds reveals correct LEDs names:

ls /sys/class/leds
blue:heartbeat  green:power  mmc0::

Seems like in Armbian they got another names. All other things should be identical. I'd start from blue one.

ls /sys/class/leds/blue:heartbeat
brightness  device  max_brightness  power  subsystem  trigger  uevent

• brightness current LED brightness;
• max_brightness will return maximum brightness available;
• trigger is tricky. On read, it will return all available tigers, that can be set to this particular LED. On write - set desired trigger if possible.

Let's check what we can set here:

cat /sys/class/leds/blue:heartbeat/trigger
none usb-gadget usb-host kbd-scrolllock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock kbd-ctrlllock kbd-ctrlrlock disk-activity disk-read disk-write mtd nand-disk [heartbeat] cpu cpu0 cpu1 cpu2 cpu3 cpu4 cpu5 cpu6 cpu7 activity default-on panic usbport mmc0 mmc1 rfkill-any rfkill-none stmmac-0:01:link stmmac-0:01:10Mbps stmmac-0:01:100Mbps stmmac-0:01:1Gbps bluetooth-power

There are a lot of different triggers to consider, but frankly I interested in setting trigger to none and call it a day.

echo "none" > /sys/class/leds/blue:heartbeat/trigger
echo "none" > /sys/class/leds/green:power/trigger
echo "none" > /sys/class/leds/mmc0::/trigger

Persisting changes

If system restarts SBC will retain its settings in hardware registries. However, if power cycle will happen settings will be lost. To restore then on boot I'll use Systemd unit and small shell script.

Systemd unit:

[Unit]
Description=Set onboard LEDs to OFF
After=network.target

[Service]
Type=oneshot
ExecStart=/opt/ledsoff/off.sh
RemainAfterExit=no

[Install]
WantedBy=multi-user.target

Shell script:

echo "none" > /sys/class/leds/blue:heartbeat/trigger
echo "none" > /sys/class/leds/green:power/trigger
echo "none" > /sys/class/leds/mmc0::/trigger

Makefile:

NAME=ledsoff

install:
  chmod +x ./${NAME}.sh
  cp ./${NAME}.service /etc/systemd/system/${NAME}.service
  systemctl daemon-reload
  systemctl enable --now ${NAME}.service

remove:
  chmod -x ./${NAME}.sh
  systemctl disable ${NAME}.service
  systemctl daemon-reload
  rm /etc/systemd/system/${NAME}.service

Now, even after power cycle changes will persist.

Bonus

I put code to my GitLab repository in case someone will need it.