目录
原理图
发光二极管与普通二极管一样是由一个PN结组成,也具有单向导电性。当给发光二极管加上正向电压后,从P区注入到N区的空穴和由N区注入到P区的电子,在PN结附近数微米内分别与N区的电子和P区的空穴复合,产生自发辐射的荧光。
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问题1:如何判断正负极?
尺寸大的LED 在极片引脚附近做有一些标记,如切角、涂色、或引脚大小不一样,一般有标志的、引脚小的、短的 一边是阴极(即负极),尺寸小的0805、0603封装的在底部有“T”字形 或 倒三角形符号“T”字一横的一边是正极; 三角形符号的“边”靠近的极性正,“角”靠近的是负极。
添加设备树
在设备树
arch/arm64/boot/dts/rockchip/rk3399pro-toybrick-prop-linux.dts
中添加
gpio-led{
status = "okay";
compatible = "gpio-led";
gpio-led1 = <&gpio1 RK_PB0 GPIO_ACTIVE_LOW>;
gpio-led2 = <&gpio1 RK_PA7 GPIO_ACTIVE_LOW>;
};
编写驱动程序
设备节点
static const struct of_device_id of_gec_leder_match[] = {
{ .compatible = "gpio-led", }, //compatible 兼容属性名,需与设备树节点的属性一致
{},
};
static struct platform_driver gec3399_led_driver = {
.driver = {
.name ="gpio-led",
.owner = THIS_MODULE,
.of_match_table = of_gec_leder_match, //设备树设备匹配
},
.probe = gec3399_led_probe, //驱动探测
.remove = gec3399_led_remove, //驱动移除
};
文件入口函数
static int gec3399_led_probe(struct platform_device *pdev)
{
int ret;
struct device_node *led_node = pdev->dev.of_node;
//第一步:获取GPIO引脚号
gpio_led1 = of_get_named_gpio(led_node,"gpio-led1", 0); //从设备树获取GPIO号
if (!gpio_is_valid(gpio_led1))
{
printk("gpio-led1: %d is invalid\n",gpio_led1);
ret = -ENODEV;
goto err_get_gpio1;
}
printk("gpio-led1 = %d\n",gpio_led1);
gpio_led2 = of_get_named_gpio(led_node,"gpio-led2", 0); //从设备树获取GPIO号
if (!gpio_is_valid(gpio_led2))
{
printk("gpio-led2: %d is invalid\n",gpio_led2);
ret = -ENODEV;
goto err_get_gpio1;
}
printk("gpio-led2 = %d\n",gpio_led2);
//第二步:申请GPIO引脚
gpio_free(gpio_led1);
ret = gpio_request(gpio_led1,"GPIO_LED1"); //申请gpio_led引脚为GPIO模式
if(ret < 0){
printk("gpio_request gpio = GPIO_LED1 error\n");
goto err_get_gpio1;
}
gpio_free(gpio_led2);
ret = gpio_request(gpio_led2,"GPIO_LED2"); //申请gpio_led引脚为GPIO模式
if(ret < 0){
printk("gpio_request gpio = GPIO_LED1 error\n");
goto err_get_gpio2;
}
//第三步:设置LED引脚的初始化电平
ret = gpio_direction_output(gpio_led1,0); //初始化LED1为关闭状态
if(ret < 0){
printk("gpio direction input gpio = LED1 error\n");
goto err_gpio_direction;
}
ret = gpio_direction_output(gpio_led2,0); //初始化LED2为关闭状态
if(ret < 0){
printk("gpio direction input gpio = LED2 error\n");
goto err_gpio_direction;
}
//第四步:通过杂项设备注册LED灯
ret = misc_register(&gec3399_led_misc); //注册字符设备
if(ret < 0){
printk("misc register error\n");
goto err_misc_register;
}
printk( KERN_ALERT "led dirve install succee\n");
return 0;
err_misc_register:
err_gpio_direction:
gpio_free(gpio_led2);
err_get_gpio2:
gpio_free(gpio_led1);
err_get_gpio1:
return ret;
}
杂项设备
static struct miscdevice gec3399_led_misc = {
.minor = MISC_DYNAMIC_MINOR,
.fops = &gec3399_led_fops,
.name = "led_drv",
}; //混杂设备结构体定义和初始化
文件操作集
static struct miscdevice gec3399_led_misc = {
.minor = MISC_DYNAMIC_MINOR,
.fops = &gec3399_led_fops,
.name = "led_drv",
}; //混杂设备结构体定义和初始化
控制函数
static long gec3399_led_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
switch(cmd)
{
case LED_ON:
gpio_set_value(gpio_led1,1);
gpio_set_value(gpio_led2,1);
break;
case LED_OFF:
gpio_set_value(gpio_led1,0);
gpio_set_value(gpio_led2,0);
break;
}
return 0;
}
完整驱动代码
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/uaccess.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>
#include <linux/device.h>
#include <linux/ioport.h>
#include <linux/ioctl.h>
#include <linux/interrupt.h>
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/wait.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#define LED_ON _IO('B',0)
#define LED_OFF _IO('B',1)
int gpio_led1,gpio_led2;
static long gec3399_led_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
switch(cmd)
{
case LED_ON:
gpio_set_value(gpio_led1,1);
gpio_set_value(gpio_led2,1);
break;
case LED_OFF:
gpio_set_value(gpio_led1,0);
gpio_set_value(gpio_led2,0);
break;
}
return 0;
}
static int gec3399_led_release(struct inode *inode, struct file *file)
{
gpio_set_value(gpio_led1,0); //应用程序退出时,关闭蜂鸣器
gpio_set_value(gpio_led2,0); //应用程序退出时,关闭蜂鸣器
return 0;
}
static const struct file_operations gec3399_led_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = gec3399_led_ioctl,
.release = gec3399_led_release,
}; //文件操作集结构体
static struct miscdevice gec3399_led_misc = {
.minor = MISC_DYNAMIC_MINOR,
.fops = &gec3399_led_fops,
.name = "led_drv",
}; //混杂设备结构体定义和初始化
static int gec3399_led_probe(struct platform_device *pdev)
{
int ret;
struct device_node *led_node = pdev->dev.of_node;
//enum of_gpio_flags flag;
printk(KERN_ALERT"gpio-led math succee\n");
gpio_led1 = of_get_named_gpio(led_node,"gpio-led1", 0); //从设备树获取GPIO号
if (!gpio_is_valid(gpio_led1))
{
printk("gpio-led1: %d is invalid\n",gpio_led1);
ret = -ENODEV;
goto err_get_gpio1;
}
printk("gpio-led1 = %d\n",gpio_led1);
gpio_led2 = of_get_named_gpio(led_node,"gpio-led2", 0); //从设备树获取GPIO号
if (!gpio_is_valid(gpio_led2))
{
printk("gpio-led2: %d is invalid\n",gpio_led2);
ret = -ENODEV;
goto err_get_gpio1;
}
printk("gpio-led2 = %d\n",gpio_led2);
gpio_free(gpio_led1);
ret = gpio_request(gpio_led1,"GPIO_LED1"); //申请gpio_led引脚为GPIO模式
if(ret < 0){
printk("gpio_request gpio = GPIO_LED1 error\n");
goto err_get_gpio1;
}
gpio_free(gpio_led2);
ret = gpio_request(gpio_led2,"GPIO_LED2"); //申请gpio_led引脚为GPIO模式
if(ret < 0){
printk("gpio_request gpio = GPIO_LED1 error\n");
goto err_get_gpio2;
}
ret = gpio_direction_output(gpio_led1,0); //初始化LED1为关闭状态
if(ret < 0){
printk("gpio direction input gpio = ak8963c_DYDR error\n");
goto err_gpio_direction;
}
ret = gpio_direction_output(gpio_led2,0); //初始化LED2为关闭状态
if(ret < 0){
printk("gpio direction input gpio = ak8963c_DYDR error\n");
goto err_gpio_direction;
}
ret = misc_register(&gec3399_led_misc); //注册字符设备
if(ret < 0){
printk("misc register error\n");
goto err_misc_register;
}
printk( KERN_ALERT "led dirve install succee\n");
return 0;
err_misc_register:
err_gpio_direction:
gpio_free(gpio_led2);
err_get_gpio2:
gpio_free(gpio_led1);
err_get_gpio1:
return ret;
}
static int gec3399_led_remove(struct platform_device *pdev)
{
gpio_free(gpio_led1);
gpio_free(gpio_led2);
misc_deregister(&gec3399_led_misc);
printk(KERN_ALERT "led dirve rmove succee\n");
return 0;
}
static const struct of_device_id of_gec_leder_match[] = {
{ .compatible = "gpio-led", }, //compatible 兼容属性名,需与设备树节点的属性一致
{},
};
static struct platform_driver gec3399_led_driver = {
.driver = {
.name ="gpio-led",
.owner = THIS_MODULE,
.of_match_table = of_gec_leder_match, //设备树设备匹配
},
.probe = gec3399_led_probe, //驱动探测
.remove = gec3399_led_remove, //驱动移除
};
module_platform_driver(gec3399_led_driver);
//module的描述,不是必需的。#modinfo led_drv.ko
MODULE_DESCRIPTION("led driver for RK3399");
MODULE_LICENSE("GPL"); //符合GPL协议
MODULE_VERSION("V1.0");
测试代码
测试代码主要实现LED的闪烁功能
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
//宏定义
#define LED_ON _IO('B',0)
#define LED_OFF _IO('B',1)
int main(void)
{
int fd_led;
int ret;
//第一步:打开设备节点
fd_led = open("/dev/led_drv", O_WRONLY);
if(fd_led < 0)
{
perror("open led driver");
return -1;
}
while(1)
{
//第二步:点亮LED灯
ret = ioctl(fd_led,LED_ON);
if(ret < 0)
perror("write led driver ");
sleep(1);
//第三步:关闭LED灯
ret = ioctl(fd_led,LED_OFF);
if(ret < 0 )
perror("write led driver ");
sleep(1);
}
//第四步:关闭设备节点
close(fd_led);
return 0;
}
Makefile文件
obj-m += led_drv.o
KERNELDIR:=/file/RK3399Pro/rk3399pro_git_repo/kernel
PWD:=$(shell pwd)
default:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
test:
aarch64-linux-gnu-gcc led_test.c -o led_test
clean:
rm -rf *.o *.order .*.cmd *.ko *.mod.c *.symvers *.tmp_versions led_test
测试步骤
编译源码
在ubuntu中输入:
make
得到驱动目标文件led_drv.ko
输入:
make test
得到测试目标文件:led_test
加载驱动
在开发板命令终端输入:
insmod led_drv.ko
执行测试程序
在开发板命令终端输入:
chmod 777 led_test
./led_test
实验现象
实现LED的闪烁