Atmark Techno Armadillo-440, Startup Manual

Page: 59 / 70

Chapter 10. Other Devices
10.1. LED
The Armadillo-400 Series LEDs are supported as LED class devices. The LEDs can be controlled with the files under
the LED class directories. For the LED class directories and corresponding LEDs, refer to Table 10.1, “LEDs and LED
Class Directories”.
Table 10.1. LEDs and LED Class Directories
LED Class Directory Description
/sys/class/leds/red/ LED3 (red)
/sys/class/leds/green/ LED4 (green)
/sys/class/leds/yellow/ LED5 (yellow)
10.1.1. Activating and Deactivating LEDs
LEDs can be turned on and off by writing an appropriate value to the brightness file under the LED class directory. A
value between 0 and 255 can be written to the brightness file.
Writing any value apart from 0 to the brightness file turns the LED on. As the Armadillo-400 Series LEDs do not have
brightness control functionality, the value has no effective meaning.
[armadillo ~]# echo 1 > /sys/class/leds/yellow/brightness
Figure 10.1. Turning LED5 On
Writing 0 to the brightness file turns the LED off.
[armadillo ~]# echo 0 > /sys/class/leds/yellow/brightness
Figure 10.2. Turning LED5 Off
The current state of the LED can be obtained by reading the brightness file. 0 represents the off state, and any other value
represents an on state.
[armadillo ~]# cat /sys/class/leds/yellow/brightness
0
Figure 10.3. Displaying LED5 State
10.1.2. Using Triggers
A trigger to turn the LED on and off can be set by writing an appropriate value to the trigger file under the LED class
directory. For values supported by the trigger file, refer to Table 10.1, “LEDs and LED Class Directories”.
Armadillo-440 LCD Model Development Set Startup Guide Other Devices
59