LED

Introduction

LEDs can be controlled by using the LED device subsystem or by
directly operating GPIO.

Controlling LEDs by device

Linux has its own LED subsystem for LED devices. In Core-1109-JD4,
LEDs are configured as LED class devices.You can control them via
"/sys/class/leds/".

Up: User-defined status

Down: The system is turned on when it is powered on.

You can change the behavior of each LED by using the echo command to
write command to its brightness property:

Upper Lights:

   echo 1 > /sys/class/leds/firefly\:yellow\:user/brightness # Upper level lights on
   echo 0 > /sys/class/leds/firefly\:yellow\:user/brightness # Upper lights off

Lower level lights:

   echo 1 > /sys/class/leds/firefly\:blue\:power/brightness # Lower level lights on
   echo 0 > /sys/class/leds/firefly\:blue\:power/brightness # Lower level lights off

Using trigger control LED

Trigger contains a variety of ways to control the LED, here with two
examples to illustrate.

Simple trigger LED

Complex trigger LED

For more information, please read the document "leds-class.txt".

First of all, we need to know how many LED definition, while the
corresponding property of the LED is.

Board:"sdk/kernel/arch/arm/boot/dts/rv1126-firefly-rk809.dtsi"：

   leds {
       compatible = "gpio-leds";

   	work {
           label = "firefly:blue:power";
           linux,default-trigger = "ir-power-click";
           gpios = <&gpio0 RK_PA4 GPIO_ACTIVE_HIGH>;
           pinctrl-names = "default";
           pinctrl-0 = <&led_power>;
           default-state = "on";
   	};
       user {
           label = "firefly:yellow:user";
           linux,default-trigger = "ir-user-click";
           gpios = <&gpio0 RK_PC0 GPIO_ACTIVE_HIGH>;
           pinctrl-names = "default";
           pinctrl-0 = <&led_user>;
           default-state = "on";
   	};
   };

   # pinctrl needs to add GPIO multiplexing control
   leds {
   	led_power: led-power {
               rockchip,pins = <0 RK_PA4 RK_FUNC_GPIO &pcfg_pull_none>;
           };

           led_user: led-user {
               rockchip,pins = <0 RK_PC0 RK_FUNC_GPIO &pcfg_pull_none>;
           };
   };

Note: The value of "compatible" must match the one in "drivers/leds
/leds-gpio.c".

Complex trigger LED

The following is the trigger mode control LED complex example, "timer
trigger" is to let the LED to achieve constant light off effect.

We need to configure the timer trigger on the kernel.

In the "kernel" path using "make menuconfig", in accordance with the
following method to chose "timer trigger" driver.

   Device Drivers
   --->LED Support
      --->LED Trigger support
         --->LED Timer Trigger

Save the configuration and compile the kernel, and burn "zboot.img" to
the Core-1109-JD4 board. We can use the serial port to input commands,
and we can see the corresponding lights flashing at intervals.

   # Upper lights flashing
   echo "timer" > /sys/class/leds/firefly\:yellow\:user/trigger

   # Lower level lights flashing
   echo "timer" > /sys/class/leds/firefly\:blue\:power/trigger

The user can also use the "cat" command to get the available values
for the trigger:

   $ cat /sys/class/leds/firefly\:yellow\:user/trigger
   none rfkill-any rfkill-none mmc0 mmc2 mmc1 [timer] oneshot heartbeat default-on rfkill0 rfkill1 rfkill2 rfkill3