网站推广工具有哪些网站的优化是什么意思

  点亮LED灯看似是一个基础的操作，但实际上，许多高级应用也依赖于高低电平的切换。例如，脉冲宽度调制（PWM）信号可以用来精确控制电机的转速，通过改变脉冲的频率和占空比，实现对电机的精确调节；同样，波形信号的生成也能够控制墨盒的喷墨精度，从而影响打印质量。通过对GPIO高低电平的精确控制，开发者可以实现各种复杂的硬件控制任务，这些基础操作为更复杂的应用提供了基础支持。
老规矩，先看效果：

这里控制led等一秒闪一次，下面分享两种控制led灯驱动代码：

1 通过GPIO 子系统设置引脚

//led1.c
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/miscdevice.h>#define DEVICE_NAME "led_clt"#define IOCTL_POWER_ON      _IO('led', 1)
#define IOCTL_POWER_OFF     _IO('POWER_OFF', 0)// 定义所有GPIO引脚 (根据实际硬件连接修改)
#define LED_PIN         101static int power_gpios[] = {LED_PIN
};static const char *power_gpio_names[] = {"LED"
};void led_light(unsigned int epoch)
{int i = 0;for(i = 0 ;i < epoch; i++){gpio_set_value(LED_PIN,1);mdelay(1000);gpio_set_value(LED_PIN,0);mdelay(1000);}}
long gpio_user_ctl(struct file *file, unsigned int cmd, unsigned long arg)
{switch (cmd) {int i;case IOCTL_POWER_ON:led_light(5);break;case IOCTL_POWER_OFF://下电时序信号printk(KERN_EMERG "inkjet power off...");break;default:return -ENOTTY;}return 0;
}static const struct file_operations power_fops = {.owner = THIS_MODULE,.unlocked_ioctl = gpio_user_ctl,  // 设置ioctl回调.open = nonseekable_open,
};
static struct miscdevice gpio_dev = {.minor = MISC_DYNAMIC_MINOR,.name = DEVICE_NAME,.fops = &power_fops,
};
// 初始化函数
static int __init power_init(void)
{int i, ret = 0;ret = register_chrdev(0, KERN_DEBUG, &power_fops);if (ret < 0) {printk(KERN_ERR "Failed to register device\n");return ret;}// 获取设备号printk(KERN_INFO "Device registered with major number %d\n", ret);// 申请所有GPIOfor (i = 0; i < ARRAY_SIZE(power_gpios); i++) {ret = gpio_request(power_gpios[i], power_gpio_names[i]);if (ret){printk(KERN_ERR "Failed to request GPIO %s (%d)\n", power_gpio_names[i], power_gpios[i]);goto error;}gpio_direction_output(power_gpios[i], 0);}//注册设备，用于内核与用户空间简单交互ret = misc_register(&gpio_dev);if (ret) {goto error;printk(KERN_ERR "Failed to register misc device\n");return ret;}// 安装驱动printk(KERN_INFO "Motor Drive Install Success\n");return 0;error:// 释放已申请的GPIOfor (i = i - 1; i >= 0; i--) {gpio_free(power_gpios[i]);}return ret;
}// 清理退出函数
static void __exit power_exit(void)
{int i;unregister_chrdev(0, DEVICE_NAME);  // 注销字符设备printk(KERN_INFO "Device unregistered\n");//释放所有GPIOfor (i = ARRAY_SIZE(power_gpios) - 1; i >= 0; i--) {gpio_free(power_gpios[i]);}misc_deregister(&gpio_dev);printk(KERN_INFO "Motor Drive Uninstall Success\n");
}module_init(power_init);
module_exit(power_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("limingzhao");
MODULE_DESCRIPTION("motor prj");

2 直接操作硬件寄存器

#include <linux/init.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/delay.h>
//msdevice
#include <linux/miscdevice.h>
#define DEV_NAME            "led_clt"#define IOCTL_POWER_ON      _IO('led', 1)
#define IOCTL_POWER_OFF     _IO('POWER_OFF', 0)#define GPIO1_COUNT            4
#define GPIO3_COUNT            11
#define GPIO4_COUNT            6#define GROUP_COUNT            5#define GPIO1_BASE (0xFE740000)
#define GPIO3_BASE (0xFE760000)
#define GPIO4_BASE (0xFE770000)///A,B-->GPIO1_DR_L和GPIO1_DDR_L///C,D-->GPIO1_DR_H和GPIO1_DDR_H//GPIO1A0,GPIO1A1,GPIO1B0,GPIO1B1-->GPIO1_DR_L和GPIO1_DDR_L
#define GPIO1_DR_L (GPIO1_BASE + 0x0000)
#define GPIO1_DDR_L (GPIO1_BASE + 0x0008)//GPIO3_A0,GPIO3_A1...-->GPIO1_DR_L和GPIO1_DDR_L
#define GPIO3_DR_L (GPIO3_BASE + 0x0000)
#define GPIO3_DDR_L (GPIO3_BASE + 0x0008)//GPIO4C3,GPIO4C5..-->GPIO2_DR_H和GPIO2_DDR_H
#define GPIO4_DR_H (GPIO4_BASE + 0x0004)
#define GPIO4_DDR_H (GPIO4_BASE + 0x000C)static dev_t devno;
struct class *inkjet_chrdev_class;typedef struct __PIN_INDEX{unsigned int  pin_index;unsigned long val_hig;unsigned long val_low;
}PIN_INDEX;typedef struct __PIN_PARAMS{struct cdev dev;unsigned int 	__iomem *va_dr; 	// 数据寄存器，设置输出的电压unsigned int 	__iomem *va_ddr; 	// 数据方向寄存器，设置输入或者输出PIN_INDEX 		arrPin[20]; // 偏移unsigned int 	pin_count;}PIN_PARAMS;///GROUP1,GROUP3,GROUP4,The Number Of Array is Five for Simplifing Coding
static PIN_PARAMS GPIO_GROUPS[GROUP_COUNT];void led_light(unsigned int epoch)
{int i = 0;for(i = 0 ;i < epoch; i++){set_hig(2);mdelay(1000);set_low(2);mdelay(1000);}}
long power_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{switch (cmd) {int i;case IOCTL_POWER_ON:led_light(5);break;case IOCTL_POWER_OFF:break;default:return -ENOTTY;}return 0;
}
static struct file_operations inkjet_chrdev_fops = {.owner = THIS_MODULE,.unlocked_ioctl = power_ioctl,  // 设置ioctl回调
};
//注册设备信息，用于内核与用户空间简单交互
static struct miscdevice gpio_dev = {.minor = MISC_DYNAMIC_MINOR,.name = DEV_NAME,.fops = &inkjet_chrdev_fops,
};
void set_hig(unsigned int index)
{/*引脚对应图pin					indexGPIO1_A0 				 0GPIO1_A1				 1GPIO3_A5				 2GPIO3_A6				 3GPIO3_A7				 4GPIO4_C3				 5GPIO4_C5				 6GPIO4_C2				 7GPIO3_B4				 8GPIO4_D2				 9GPIO3_B6				 10GPIO3_B5				 11GPIO3_B7				 12GPIO3_B1				 13GPIO3_A0				 14GPIO4_C6				 15GPIO4_C4				 16GPIO3_B3				 17GPIO3_B2				 18GPIO1_B0				 19GPIO1_B1				 20*/if(index == 0){	//GPIO1_A0volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[0].val_hig;}else if(index == 1){	//GPIO1_A1volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[1].val_hig;}else if(index == 2){	//GPIO3_A5volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[0].val_hig;}else if(index == 3){	//GPIO3_A6volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[1].val_hig;}else if(index == 4){	//GPIO3_A7volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[2].val_hig;}else if(index == 5){	//GPIO4_C3volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[0].val_hig;}else if(index == 6){	//GPIO4_C5volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[1].val_hig;}else if(index == 7){	//GPIO4_C2volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[2].val_hig;}else if(index == 8){	//GPIO3_B4volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[3].val_hig;}else if(index == 9){	//GPIO4_D2volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[3].val_hig;}else if(index == 10){	//GPIO3_B6volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[4].val_hig;}else if(index == 11){	//GPIO3_B5volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[5].val_hig;}else if(index == 12){	//GPIO3_B7volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[6].val_hig;}else if(index == 13){	//GPIO3_B1volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[7].val_hig;}else if(index == 14){	//GPIO3_A0volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[8].val_hig;}else if(index == 15){	//GPIO4_C6volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[4].val_hig;}else if(index == 16){	//GPIO4_C4volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[5].val_hig;}else if(index == 17){	//GPIO3_B3volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[9].val_hig;}else if(index == 18){	//GPIO3_B2volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[10].val_hig;}else if(index == 19){	//GPIO1_B0volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[2].val_hig;}else if(index == 20){	//GPIO1_B1volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[3].val_hig;}else{printk(KERN_EMERG "set_hig input index error!!\n");}}
void set_low(unsigned int index)
{/*引脚对应图pin					indexGPIO1_A0 				 0GPIO1_A1				 1GPIO3_A5				 2GPIO3_A6				 3GPIO3_A7				 4GPIO4_C3				 5GPIO4_C5				 6GPIO4_C2				 7GPIO3_B4				 8GPIO4_D2				 9GPIO3_B6				 10GPIO3_B5				 11GPIO3_B7				 12GPIO3_B1				 13GPIO3_A0				 14GPIO4_C6				 15GPIO4_C4				 16GPIO3_B3				 17GPIO3_B2				 18GPIO1_B0				 19GPIO1_B1				 20*/if(index == 0){	//GPIO1_A0volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[0].val_low;}else if(index == 1){	//GPIO1_A1volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[1].val_low;}else if(index == 2){	//GPIO3_A5volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[0].val_low;}else if(index == 3){	//GPIO3_A6volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[1].val_low;}else if(index == 4){	//GPIO3_A7volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[2].val_low;}else if(index == 5){	//GPIO4_C3volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[0].val_low;}else if(index == 6){	//GPIO4_C5volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[1].val_low;}else if(index == 7){	//GPIO4_C2volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[2].val_low;}else if(index == 8){	//GPIO3_B4volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[3].val_low;}else if(index == 9){	//GPIO4_D2volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[3].val_low;}else if(index == 10){	//GPIO3_B6volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[4].val_low;}else if(index == 11){	//GPIO3_B5volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[5].val_low;}else if(index == 12){	//GPIO3_B7volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[6].val_low;}else if(index == 13){	//GPIO3_B1volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[7].val_low;}else if(index == 14){	//GPIO3_A0volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[8].val_low;}else if(index == 15){	//GPIO4_C6volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[4].val_low;}else if(index == 16){	//GPIO4_C4volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);*reg = GPIO_GROUPS[4].arrPin[5].val_low;}else if(index == 17){	//GPIO3_B3volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[9].val_low;}else if(index == 18){	//GPIO3_B2volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);*reg = GPIO_GROUPS[3].arrPin[10].val_low;}else if(index == 19){	//GPIO1_B0volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[2].val_low;}else if(index == 20){	//GPIO1_B1volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);*reg = GPIO_GROUPS[1].arrPin[3].val_low;}else{printk(KERN_EMERG "set_low input index error!!\n");}}
void init_pin_values()
{int i = 0;int j = 0;dev_t cur_dev;unsigned long val = 0;////////GPIO1 GROUP SETTING//////GPIO_GROUPS[1].pin_count = GPIO1_COUNT;//GPIO1_A0GPIO_GROUPS[1].arrPin[0].pin_index = 0;//GPIO1_A1GPIO_GROUPS[1].arrPin[1].pin_index = 1;//GPIO1_B0GPIO_GROUPS[1].arrPin[2].pin_index = 8;//GPIO1_B1GPIO_GROUPS[1].arrPin[3].pin_index = 9;GPIO_GROUPS[1].va_dr = ioremap(GPIO1_DR_L, 4);GPIO_GROUPS[1].va_ddr = ioremap(GPIO1_DDR_L, 4);////////GPIO3 GROUP SETTING//////GPIO_GROUPS[3].pin_count = GPIO3_COUNT;//GPIO3_A5GPIO_GROUPS[3].arrPin[0].pin_index = 5;//GPIO3_A6GPIO_GROUPS[3].arrPin[1].pin_index = 6;//GPIO3_A7GPIO_GROUPS[3].arrPin[2].pin_index = 7;//GPIO3_B4GPIO_GROUPS[3].arrPin[3].pin_index = 12;//GPIO3_B6GPIO_GROUPS[3].arrPin[4].pin_index = 14;//GPIO3_B5GPIO_GROUPS[3].arrPin[5].pin_index = 13;//GPIO3_B7GPIO_GROUPS[3].arrPin[6].pin_index = 15;//GPIO3_B1GPIO_GROUPS[3].arrPin[7].pin_index = 9;//GPIO3_A0GPIO_GROUPS[3].arrPin[8].pin_index = 0;//GPIO3_B3GPIO_GROUPS[3].arrPin[9].pin_index = 11;//GPIO3_B2GPIO_GROUPS[3].arrPin[10].pin_index = 10;GPIO_GROUPS[3].va_dr = ioremap(GPIO3_DR_L, 4);GPIO_GROUPS[3].va_ddr = ioremap(GPIO3_DDR_L, 4);////////GPIO4 GROUP SETTING//////GPIO_GROUPS[4].pin_count = GPIO4_COUNT;//GPIO4_C3GPIO_GROUPS[4].arrPin[0].pin_index = 3;//GPIO4_C5GPIO_GROUPS[4].arrPin[1].pin_index = 5;//GPIO4_C2GPIO_GROUPS[4].arrPin[2].pin_index = 2;//GPIO4_D2GPIO_GROUPS[4].arrPin[3].pin_index = 10;//GPIO4_C6GPIO_GROUPS[4].arrPin[4].pin_index = 6;//GPIO4_C4GPIO_GROUPS[4].arrPin[5].pin_index = 4;GPIO_GROUPS[4].va_dr = ioremap(GPIO4_DR_H, 4);GPIO_GROUPS[4].va_ddr = ioremap(GPIO4_DDR_H, 4);alloc_chrdev_region(&devno, 0, GROUP_COUNT - 2, DEV_NAME);inkjet_chrdev_class = class_create(THIS_MODULE, "led_clt");for (; i < GROUP_COUNT; i++) {if(i == 0|| i == 2){continue;}cdev_init(&GPIO_GROUPS[i].dev, &inkjet_chrdev_fops);GPIO_GROUPS[i].dev.owner = THIS_MODULE;cur_dev = MKDEV(MAJOR(devno), MINOR(devno) + i);cdev_add(&GPIO_GROUPS[i].dev, cur_dev, 1);device_create(inkjet_chrdev_class, NULL, cur_dev, NULL,DEV_NAME "%d", i);}// printk(KERN_EMERG "open\n");////////GPIO0 GROUP PINS EXPORT AND SAVE VALUE////////五组GPIO(GPIO0-GPIO4)for(i = 0; i < GROUP_COUNT; i++){if(i == 0|| i == 2){continue;}for(j = 0; j < GPIO_GROUPS[i].pin_count; j++){//exportval = ioread32(GPIO_GROUPS[i].va_ddr);val |= ((unsigned int)0x1 << (GPIO_GROUPS[i].arrPin[j].pin_index+16));val |= ((unsigned int)0X1 << (GPIO_GROUPS[i].arrPin[j].pin_index));iowrite32(val, GPIO_GROUPS[i].va_ddr);//save hig and low value//high valueval = ioread32(GPIO_GROUPS[i].va_dr);val |= ((unsigned int)0x1 << (GPIO_GROUPS[i].arrPin[j].pin_index+16));val &= ~((unsigned int)0x01 << (GPIO_GROUPS[i].arrPin[j].pin_index));   iowrite32(val, GPIO_GROUPS[i].va_dr);GPIO_GROUPS[i].arrPin[j].val_low = val;//low valueval = ioread32(GPIO_GROUPS[i].va_dr);val |= ((unsigned int)0x1 << (GPIO_GROUPS[i].arrPin[j].pin_index+16));val |= ((unsigned int)0x1 << (GPIO_GROUPS[i].arrPin[j].pin_index));iowrite32(val, GPIO_GROUPS[i].va_dr);GPIO_GROUPS[i].arrPin[j].val_hig = val;}}int ret = 0;//注册设备，用于内核与用户空间简单交互ret = misc_register(&gpio_dev);if (ret) {printk(KERN_ERR "Failed to register misc device\n");return;}}static __init int inkjet_chrdev_init(void)
{init_pin_values();return 0;
}module_init(inkjet_chrdev_init);static __exit void inkjet_chrdev_exit(void)
{int i;dev_t cur_dev;for (i = 0; i < GROUP_COUNT; i++) {if(i == 0|| i == 2){continue;}iounmap(GPIO_GROUPS[i].va_dr); 		// 释放模式寄存器虚拟地址iounmap(GPIO_GROUPS[i].va_ddr); 	// 释放输出类型寄存器虚拟地址}for (i = 0; i < GROUP_COUNT; i++) {if(i == 0|| i == 2){continue;}cur_dev = MKDEV(MAJOR(devno), MINOR(devno) + i);device_destroy(inkjet_chrdev_class, cur_dev);cdev_del(&GPIO_GROUPS[i].dev);}unregister_chrdev_region(devno, 1);class_destroy(inkjet_chrdev_class);//release access devmisc_deregister(&gpio_dev);
}module_exit(inkjet_chrdev_exit);MODULE_AUTHOR("limingzhao");
MODULE_LICENSE("GPL");

这里我嫌示例代码太麻烦了，自己封装了一下，set_hig和set_low,只封装了GPIO1、GPIO3和GPIO4，对应序号的gpio口在注释里面，方便使用。

3 makefile部分

KERNEL_DIR=/home/path/to/kernel/ARCH=arm64
CROSS_COMPILE=aarch64-linux-gnu-
export  ARCH  CROSS_COMPILEKBUILD_CFLAGS += -O0 -Wall 
obj-m := led1.oall:$(MAKE) -C $(KERNEL_DIR) M=$(CURDIR) modules.PHONE:cleanclean:$(MAKE) -C $(KERNEL_DIR) M=$(CURDIR) clean	

注:这里的KERNEL_DIR改成你自己编译的内核路径，如果不知道怎么编译的可以看我写的驱动开发(1)部分
这里的驱动代码和makefile放虚拟机里面(x86_64)，编译成ko文件后放入驱动板里面安装，如图所示：

我这里的led1.c和led2.c分别对应本文段落1和本文段部落2的代码，这两种方法的优劣势上篇文章已经讲明白了。唯一的一点是上次纠正我上篇文章中的错误：上篇文章说通过直接操作寄存器的方式拉高再拉低，寄存器只能到达160ns左右是错误的，因为我之前用的示波器精度不够，这里直接操作寄存器的驱动代码完全能达到50ns级别的延时，不过我还是没用rk3568来直接操控，想要精确操控波形，感兴趣的可以研究一下FPGA开发板。

4 用户层代码

//call_led.c
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/ioctl.h>// 定义IOCTL命令
#define IOCTL_POWER_ON      _IO('led', 1)
#define IOCTL_POWER_OFF     _IO('POWER_OFF', 0)#define DEVICE_NAME "/dev/led_clt"int main() 
{int fd;int ret;// 打开设备文件fd = open(DEVICE_NAME, O_RDWR);if (fd < 0) {perror("Failed to open device");return -1;}// 调用IOCTL_POWER_ONret = ioctl(fd, IOCTL_POWER_ON);if (ret < 0) {perror("Failed to send IOCTL_POWER_ON");close(fd);return -1;}printf("Motor started\n");sleep(5);ret = ioctl(fd, IOCTL_POWER_ON);if (ret < 0) {perror("Failed to send IOCTL_POWER_ON");close(fd);return -1;}sleep(5);// 关闭设备文件close(fd);return 0;
}

这里是通过操作led_clt设备，来控制led灯电平高低，linux果然是万物皆文件，都是通过open、read、write基本操作函数。
这里可以看到 ret = ioctl(fd, IOCTL_POWER_ON);调用了两次，也就是led灯先闪烁5次，延时5秒然后再闪烁5次。

5 安装卸载驱动命令

# install
insmod led1.ko
# uninstall
rmmod led1.c

6 使用引脚

这里使用的引脚是GPIO3_A5,如图所示:

板子具体位置：

总结

  这篇文章主要分享了在RK3568平台上控制GPIO的两种常见方式，并通过LED灯的实验测试，验证了这两种方法的效果。首先介绍了通过编程接口操作GPIO的基本原理和步骤，包括如何设置输入输出模式、读取和写入数据。后续这一系列将暂时停更，主要想先写CV和NLP算法方面的文章。