硬件信息

内核版本：Linux 4.9

硬件原理：

1. GPIO 通过一颗 MOS 管(2N7002ET1G)，接到 LED 负极，LED 正极接电源。
2. GPIO 通过拉高导通 MOS ，将 LED 接地，实现点亮 LED。

内核配置

配置内核驱动：make ARCH=arm64 menuconfig

Device Drivers  --->
	-*- LED Support  --->
		<*>   LED Support for GPIO connected LEDs 
		-*-   LED Trigger support  --->
			<*>   LED Timer Trigger 
			<*>   LED One-shot Trigger 
			<*>   LED Heartbeat Trigger
			<*>   LED backlight Trigger 
			[*]   LED CPU Trigger  
			<*>   LED GPIO Trigger 
			<*>   LED Default ON Trigger

配置文件

配置硬件信息：sys_config.fex

全志平台便捷方式配置，也可以使用通用的 dts 配置方式

[leds]
compatible = "gpio-leds";

[leds/red]
label = "red";
linux,default-trigger = "timer"
gpio = port:PL08<1><default><default><0>

[leds/blue]
label = "blue";
linux,default-trigger = "heartbeat"
gpio = port:PL07<1><default><default><0>

使用方法

正常情况下可以看到两颗灯以不同的节奏闪烁

1. 检查相应设备节点

root@localhost:/# ls /sys/class/leds
blue  red

root@linux:/# ls /sys/class/leds/blue
brightness  device  invert  max_brightness  power  subsystem  trigger  uevent

root@linux:/# ls /sys/class/leds/red
brightness  delay_on  max_brightness  subsystem  uevent
delay_off   device    power           trigger

2. 关闭触发功能

root@linux:/# echo "none" > /sys/class/leds/blue/trigger
root@linux:/# echo "none" > /sys/class/leds/red/trigger

3. 点亮关闭指定 LED（高亮、低灭）

root@linux:/# echo 1 > /sys/class/leds/blue/brightness
root@linux:/# echo 0 > /sys/class/leds/blue/brightness

4. 设置定时闪烁 LED（亮 100ms，灭 1000ms）

root@linux:/# echo "timer" > /sys/class/leds/blue/trigger        
root@linux:/# echo 100 > /sys/class/leds/blue/delay_on
root@linux:/# echo 1000 > /sys/class/leds/blue/delay_off