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
c
//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 101
static 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GPIO
for (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GPIO
for (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GPIO
for (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
c
#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 index
GPIO1_A0 0
GPIO1_A1 1
GPIO3_A5 2
GPIO3_A6 3
GPIO3_A7 4
GPIO4_C3 5
GPIO4_C5 6
GPIO4_C2 7
GPIO3_B4 8
GPIO4_D2 9
GPIO3_B6 10
GPIO3_B5 11
GPIO3_B7 12
GPIO3_B1 13
GPIO3_A0 14
GPIO4_C6 15
GPIO4_C4 16
GPIO3_B3 17
GPIO3_B2 18
GPIO1_B0 19
GPIO1_B1 20
*/
if(index == 0)
{ //GPIO1_A0
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);
*reg = GPIO_GROUPS[1].arrPin[0].val_hig;
}
else if(index == 1)
{ //GPIO1_A1
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);
*reg = GPIO_GROUPS[1].arrPin[1].val_hig;
}
else if(index == 2)
{ //GPIO3_A5
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[0].val_hig;
}
else if(index == 3)
{ //GPIO3_A6
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[1].val_hig;
}
else if(index == 4)
{ //GPIO3_A7
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[2].val_hig;
}
else if(index == 5)
{ //GPIO4_C3
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[0].val_hig;
}
else if(index == 6)
{ //GPIO4_C5
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[1].val_hig;
}
else if(index == 7)
{ //GPIO4_C2
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[2].val_hig;
}
else if(index == 8)
{ //GPIO3_B4
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[3].val_hig;
}
else if(index == 9)
{ //GPIO4_D2
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[3].val_hig;
}
else if(index == 10)
{ //GPIO3_B6
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[4].val_hig;
}
else if(index == 11)
{ //GPIO3_B5
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[5].val_hig;
}
else if(index == 12)
{ //GPIO3_B7
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[6].val_hig;
}
else if(index == 13)
{ //GPIO3_B1
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[7].val_hig;
}
else if(index == 14)
{ //GPIO3_A0
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[8].val_hig;
}
else if(index == 15)
{ //GPIO4_C6
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[4].val_hig;
}
else if(index == 16)
{ //GPIO4_C4
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[5].val_hig;
}
else if(index == 17)
{ //GPIO3_B3
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[9].val_hig;
}
else if(index == 18)
{ //GPIO3_B2
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[10].val_hig;
}
else if(index == 19)
{ //GPIO1_B0
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);
*reg = GPIO_GROUPS[1].arrPin[2].val_hig;
}
else if(index == 20)
{ //GPIO1_B1
volatile 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 index
GPIO1_A0 0
GPIO1_A1 1
GPIO3_A5 2
GPIO3_A6 3
GPIO3_A7 4
GPIO4_C3 5
GPIO4_C5 6
GPIO4_C2 7
GPIO3_B4 8
GPIO4_D2 9
GPIO3_B6 10
GPIO3_B5 11
GPIO3_B7 12
GPIO3_B1 13
GPIO3_A0 14
GPIO4_C6 15
GPIO4_C4 16
GPIO3_B3 17
GPIO3_B2 18
GPIO1_B0 19
GPIO1_B1 20
*/
if(index == 0)
{ //GPIO1_A0
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);
*reg = GPIO_GROUPS[1].arrPin[0].val_low;
}
else if(index == 1)
{ //GPIO1_A1
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);
*reg = GPIO_GROUPS[1].arrPin[1].val_low;
}
else if(index == 2)
{ //GPIO3_A5
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[0].val_low;
}
else if(index == 3)
{ //GPIO3_A6
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[1].val_low;
}
else if(index == 4)
{ //GPIO3_A7
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[2].val_low;
}
else if(index == 5)
{ //GPIO4_C3
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[0].val_low;
}
else if(index == 6)
{ //GPIO4_C5
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[1].val_low;
}
else if(index == 7)
{ //GPIO4_C2
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[2].val_low;
}
else if(index == 8)
{ //GPIO3_B4
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[3].val_low;
}
else if(index == 9)
{ //GPIO4_D2
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[3].val_low;
}
else if(index == 10)
{ //GPIO3_B6
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[4].val_low;
}
else if(index == 11)
{ //GPIO3_B5
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[5].val_low;
}
else if(index == 12)
{ //GPIO3_B7
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[6].val_low;
}
else if(index == 13)
{ //GPIO3_B1
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[7].val_low;
}
else if(index == 14)
{ //GPIO3_A0
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[8].val_low;
}
else if(index == 15)
{ //GPIO4_C6
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[4].val_low;
}
else if(index == 16)
{ //GPIO4_C4
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[4].va_dr);
*reg = GPIO_GROUPS[4].arrPin[5].val_low;
}
else if(index == 17)
{ //GPIO3_B3
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[9].val_low;
}
else if(index == 18)
{ //GPIO3_B2
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[3].va_dr);
*reg = GPIO_GROUPS[3].arrPin[10].val_low;
}
else if(index == 19)
{ //GPIO1_B0
volatile uint32_t *reg = (volatile uint32_t *)(GPIO_GROUPS[1].va_dr);
*reg = GPIO_GROUPS[1].arrPin[2].val_low;
}
else if(index == 20)
{ //GPIO1_B1
volatile 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_A0
GPIO_GROUPS[1].arrPin[0].pin_index = 0;
//GPIO1_A1
GPIO_GROUPS[1].arrPin[1].pin_index = 1;
//GPIO1_B0
GPIO_GROUPS[1].arrPin[2].pin_index = 8;
//GPIO1_B1
GPIO_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_A5
GPIO_GROUPS[3].arrPin[0].pin_index = 5;
//GPIO3_A6
GPIO_GROUPS[3].arrPin[1].pin_index = 6;
//GPIO3_A7
GPIO_GROUPS[3].arrPin[2].pin_index = 7;
//GPIO3_B4
GPIO_GROUPS[3].arrPin[3].pin_index = 12;
//GPIO3_B6
GPIO_GROUPS[3].arrPin[4].pin_index = 14;
//GPIO3_B5
GPIO_GROUPS[3].arrPin[5].pin_index = 13;
//GPIO3_B7
GPIO_GROUPS[3].arrPin[6].pin_index = 15;
//GPIO3_B1
GPIO_GROUPS[3].arrPin[7].pin_index = 9;
//GPIO3_A0
GPIO_GROUPS[3].arrPin[8].pin_index = 0;
//GPIO3_B3
GPIO_GROUPS[3].arrPin[9].pin_index = 11;
//GPIO3_B2
GPIO_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_C3
GPIO_GROUPS[4].arrPin[0].pin_index = 3;
//GPIO4_C5
GPIO_GROUPS[4].arrPin[1].pin_index = 5;
//GPIO4_C2
GPIO_GROUPS[4].arrPin[2].pin_index = 2;
//GPIO4_D2
GPIO_GROUPS[4].arrPin[3].pin_index = 10;
//GPIO4_C6
GPIO_GROUPS[4].arrPin[4].pin_index = 6;
//GPIO4_C4
GPIO_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++)
{
//export
val = 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 value
val = 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 value
val = 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 dev
misc_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
bash
KERNEL_DIR=/home/path/to/kernel/
ARCH=arm64
CROSS_COMPILE=aarch64-linux-gnu-
export ARCH CROSS_COMPILE
KBUILD_CFLAGS += -O0 -Wall
obj-m := led1.o
all:
$(MAKE) -C $(KERNEL_DIR) M=$(CURDIR) modules
.PHONE:clean
clean:
$(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
c
//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_ON
ret = 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
bash
# install
insmod led1.ko
# uninstall
rmmod led1.c6 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。