LED sysfs 4.9.y
From embeddedTS Manuals
The kernel provides access to control the LEDs using the sysfs interface:
# Set Red led on
echo 1 > /sys/class/leds/red-led/brightness
# Set Red led off
echo 0 > /sys/class/leds/red-led/brightness
# Set Green led on
echo 1 > /sys/class/leds/green-led/brightness
# Set Green led off
echo 0 > /sys/class/leds/green-led/brightness
The kernel provides various triggers that can be useful for debugging purposes. The trigger file for a given LED is in its named sub-directory, e.g.
echo "heartbeat" > /sys/class/leds/red-led/trigger
| Trigger value | LED toggles on |
|---|---|
| none | Default, no action, manually controlled by brightness file
|
| rc-feedback | IR Reciever trigger [1] |
| can0-tx | CAN0 transmit activity |
| can0-rx | CAN0 receive activity |
| can0-rxtx | CAN0 activity |
| can1-tx | CAN1 transmit activity |
| can1-rx | CAN1 receive activity |
| can1-rxtx | CAN1 activity |
| mmc0 | microSD activity |
| mmc1 | eMMC activity |
| timer | 2hz blink |
| oneshot | Blinks after delay. [2] |
| heartbeat | Similar to timer, but varies the period based on system load |
| backlight | Toggles on FB_BLANK |
| gpio | Toggle based on a specified gpio. [3] |
| cpu0 | Blink on CPU core 0 activity |
| default-on | Only turns on by default. Only useful for device tree. |
| transient | Specify on/off with time to turn off. [4] |
- ↑ There is no IR directly on the TS-4100, this would be from a USB peripheral.
- ↑ See the Kernel documentation for more details on "oneshot" operation.
- ↑ When this trigger is set, a "gpio" file appears in the same directory which can be used to specify what GPIO to follow when it blinks
- ↑ See the Kernel documentation for more details on "transient" operation.
Reading the contents of the trigger will list all compatible triggers as well as the current trigger set. The currently set trigger is indicated by surrounding brackets, e.g. none [timer] cpu ...