LED
Update time：2018-04-17 Views：2466
Introduction
There are 2 LEDs on the Firefly-RK3128 development board, as the following table shows:
| LED | GPIO |
|---|---|
| Blue | GPIO1_C7 |
| Yellow | GPIO1_C6 |
Both are programmable using ether LEDs class devices or GPIOs.
LEDs as Class Devices
Linux has its own LED subsystem for LED devices. In Firefly-RK3128, 2 LEDs are configured as LED class devices.
You can control them via /sys/class/leds/.
For more information, please read the document leds-class.txt .
The default status of the two on-board leds are:
Blue: on after the system powers on.
Yellow: defined by user.
You can change the behavior of each LED by using the echo command to write command to its trigger property:
root@firefly:~ # echo none >/sys/class/leds/firefly:blue:power/trigger root@firefly:~ # echo default-on >/sys/class/leds/firefly:blue:power/trigger
You can also use the cat command to list all available values of the trigger attribute:
root@firefly:~ # cat /sys/class/leds/firefly:blue:power/trigger none [ir-power-click] test_ac-online test_battery-charging-or-full test_battery-charging test_battery-full test_battery-charging-blink-full-solid test_usb-online mmc0 mmc1 mmc2 backlight default-on rfkill0 rfkill1 rfkill2
Controlling LED in the Kernel
The steps to control LED in the kernel are shown below:
1. Define LED node in the dts file.
Define LED node in file kernel/arch/arm/boot/dts/rk3128-fireprime.dts:
leds {compatible = "gpio-leds";power {label = "firefly:blue:power";linux,default-trigger = "ir-power-click";default-state = "on";gpios = <&gpio1 GPIO_C7 GPIO_ACTIVE_LOW>;};user {label = "firefly:yellow:user";linux,default-trigger = "ir-user-click";default-state = "off";gpios = <&gpio1 GPIO_C6 GPIO_ACTIVE_LOW>;};};Note: The value of .compatible must match the one in drivers/leds/leds-gpio.c.
2. Include head files in the driver.
#include <linux/leds.h>
3. Control the LED in the drivers.
(1). Define a trigger.
DEFINE_LED_TRIGGER(ledtrig_ir_click);
(2). Register the trigger.
led_trigger_register_simple("ir-power-click", &ledtrig_ir_click);(3). Turn on/off the LED.
led_trigger_event(ledtrig_ir_click, LED_FULL); //ONled_trigger_event(ledtrig_ir_click, LED_OFF); //OFF
