Linux驱动之定时器在按键去抖中的应用-白红宇的个人博客

发布日期：2021-08-16 13:28:01 浏览次数：57 分类：技术文章

本文共 7677 字，大约阅读时间需要 25 分钟。

机械按键在按下的过程中会出现抖动的情况，如下图，这样就会导致本来按下一次按键的过程会出现多次中断，导致判断出错。在按键驱动程序中我们可以这么做：

在按键驱动程序中我们可以这么做来取消按键抖动的影响：当出现一个按键中断后不会马上去处理它，而是延时一个抖动时间（一般10ms），如果在这个时间内再次出现中断那么再次延时10ms。这样循环，一直到在这个10ms内只有一个按键中断，那么就认为这次是真的按键值，然后在定时器处理函数里处理它。上述过程可以利用内核的定时器来实现。

定时器二要素：定时时间、定时时间到后做什么事情。根据这两个要素来编写程序，直接在sixth_drv.c的驱动程序上更改直接看到代码：

1、定时器的创建，先建立一个定时器结构

static struct timer_list buttons_timer;//定义一个定时器

2、在模块装载时初始化定时器

static int sixth_drv_init(void){    /*增加一个定时器用于处理按键抖动*/    init_timer(&buttons_timer);    buttons_timer.expires = 0;//定时器的定时时间//    buttons_timer->data = (unsigned long) cs;    buttons_timer.function = buttons_timeout;//定时时间到后的处理函数    add_timer(&buttons_timer);//将定义的定时器放入定时器链表        sixthmajor = register_chrdev(0, "buttons", &sixth_drv_ops);//注册驱动程序    if(sixthmajor < 0)        printk("failes 1 buttons_drv register\n");        sixth_drv_class = class_create(THIS_MODULE, "buttons");//创建类    if(sixth_drv_class < 0)        printk("failes 2 buttons_drv register\n");    sixth_drv_class_dev = class_device_create(sixth_drv_class, NULL, MKDEV(sixthmajor,0), NULL,"buttons");//创建设备节点    if(sixth_drv_class_dev < 0)        printk("failes 3 buttons_drv register\n");        gpfcon = ioremap(0x56000050, 16);//重映射    gpfdat = gpfcon + 1;    gpgcon = ioremap(0x56000060, 16);//重映射    gpgdat = gpgcon + 1;    printk("register buttons_drv\n");    return 0;}

3、编写定时器处理函数

static void buttons_timeout(unsigned long data){    unsigned int pin_val;    static long cnt=0;        //printk("timeout cnt : %d\n",++cnt);    if(pin_des==NULL)        return;    else    {    //    printk("pin_des != NULL\n");                pin_val = s3c2410_gpio_getpin(pin_des->pin);                if(pin_val) //按键松开            key_val = 0x80 | pin_des->key_val;        else            key_val = pin_des->key_val;        wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */        ev_press = 1;                    kill_fasync(&sixth_fasync, SIGIO, POLL_IN);//发生信号给进程    }}

4、当在卸载驱动时将定时器删除；在中断处理程序中直接改变定时器的超时时间，并记录下是哪个按键按下的即可，其他处理都在定时器超时函数中。直接看到完整代码：

#include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
                   //含有iomap函数iounmap函数#include 
           
            //含有copy_from_user函数#include 
            
             //含有类相关的处理函数#include 
             
              //含有S3C2410_GPF0等相关的#include 
              
                //含有IRQ_HANDLED\IRQ_TYPE_EDGE_RISING#include 
               
                 //含有IRQT_BOTHEDGE触发类型#include 
                
                  //含有request_irq、free_irq函数#include 
                 
                  #include 
                  
                    //含有各种错误返回值//#include 
                   
                    static struct class *sixth_drv_class;//类static struct class_device *sixth_drv_class_dev;//类下面的设备static int sixthmajor;static unsigned long *gpfcon = NULL;static unsigned long *gpfdat = NULL;static unsigned long *gpgcon = NULL;static unsigned long *gpgdat = NULL;struct fasync_struct *sixth_fasync; static unsigned int key_val;struct pin_desc { unsigned int pin; unsigned int key_val;};static struct pin_desc pins_desc[4] = { {S3C2410_GPF0,0x01}, {S3C2410_GPF2,0x02}, {S3C2410_GPG3,0x03}, {S3C2410_GPG11,0x04}};static struct pin_desc *pin_des=NULL;static unsigned int ev_press;static DECLARE_WAIT_QUEUE_HEAD(button_waitq);//注册一个等待队列button_waitq static atomic_t open_flag = ATOMIC_INIT(1); //定义原子变量open_flag 并初始化为1static DECLARE_MUTEX(button_lock); //定义互斥锁static struct timer_list buttons_timer;//定义一个定时器/* *0x01、0x02、0x03、0x04表示按键被按下 */ /* *0x81、0x82、0x83、0x84表示按键被松开 *//* *利用dev_id的值为pins_desc来判断是哪一个按键被按下或松开 */static irqreturn_t buttons_irq(int irq, void *dev_id){ pin_des = (struct pin_desc *)dev_id;//取得哪个按键被按下的状态 mod_timer(&buttons_timer, jiffies+HZ/100);//10ms之后调用定时器处理函数 return IRQ_HANDLED;}static int sixth_drv_open (struct inode * inode, struct file * file){ int ret;// if(atomic_dec_and_test(&open_flag)==0)//自检后是否为0,不为0说明已经被人调用// {// atomic_inc(&open_flag);//原子变量+1// return -EBUSY;// } if(file->f_flags & O_NONBLOCK)//非阻塞方式 { if(down_trylock(&button_lock))//获取信号量失败则返回 return -EBUSY; } else down(&button_lock);//获得信号量 ret = request_irq(IRQ_EINT0, buttons_irq, IRQT_BOTHEDGE, "s1", (void * )&pins_desc[0]); if(ret) { printk("open failed 1\n"); return -1; } ret = request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, "s2", (void * )& pins_desc[1]); if(ret) { printk("open failed 2\n"); return -1; } ret = request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "s3", (void * )&pins_desc[2]); if(ret) { printk("open failed 3\n"); return -1; } ret = request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "s4", (void * )&pins_desc[3]); if(ret) { printk("open failed 4\n"); return -1; } return 0;}static int sixth_drv_close(struct inode * inode, struct file * file){// atomic_inc(&open_flag);//原子变量+1 up(&button_lock);//释放信号量 free_irq(IRQ_EINT0 ,(void * )&pins_desc[0]); free_irq(IRQ_EINT2 ,(void * )& pins_desc[1]); free_irq(IRQ_EINT11 ,(void * )&pins_desc[2]); free_irq(IRQ_EINT19 ,(void * )&pins_desc[3]); return 0;}static ssize_t sixth_drv_read(struct file * file, char __user * userbuf, size_t count, loff_t * off){ int ret; if(count != 1) { printk("read error\n"); return -1; } if(file->f_flags & O_NONBLOCK)//非阻塞方式 { if(!ev_press)//判断是否有按键按下，如果没有直接返回 { key_val = 0; ret = copy_to_user(userbuf, &key_val, 1); return -EBUSY; } } else//如果没有按键动作，直接进入休眠 wait_event_interruptible(button_waitq, ev_press);//将当前进程放入等待队列button_waitq中 ret = copy_to_user(userbuf, &key_val, 1); ev_press = 0;//按键已经处理可以继续睡眠 if(ret) { printk("copy error\n"); return -1; } return 1;}static unsigned int sixth_drv_poll(struct file *file, poll_table *wait){ unsigned int ret = 0; poll_wait(file, &button_waitq, wait);//将当前进程放到button_waitq列表 if(ev_press) ret |=POLLIN;//说明有数据被取到了 return ret;}static int sixth_drv_fasync(int fd, struct file * file, int on){ int err; printk("fansync_helper\n"); err = fasync_helper(fd, file, on, &sixth_fasync);//初始化sixth_fasync if (err < 0) return err; return 0;}static struct file_operations sixth_drv_ops = { .owner = THIS_MODULE, .open = sixth_drv_open, .read = sixth_drv_read, .release = sixth_drv_close, .poll = sixth_drv_poll, .fasync = sixth_drv_fasync, };static void buttons_timeout(unsigned long data){ unsigned int pin_val; static long cnt=0; //printk("timeout cnt : %d\n",++cnt); if(pin_des==NULL) return; else { // printk("pin_des != NULL\n"); pin_val = s3c2410_gpio_getpin(pin_des->pin); if(pin_val) //按键松开 key_val = 0x80 | pin_des->key_val; else key_val = pin_des->key_val; wake_up_interruptible(&button_waitq); /* 唤醒休眠的进程 */ ev_press = 1; kill_fasync(&sixth_fasync, SIGIO, POLL_IN);//发生信号给进程 }}static int sixth_drv_init(void){ /*增加一个定时器用于处理按键抖动*/ init_timer(&buttons_timer); buttons_timer.expires = 0;//定时器的定时时间// buttons_timer->data = (unsigned long) cs; buttons_timer.function = buttons_timeout;//定时时间到后的处理函数 add_timer(&buttons_timer);//将定义的定时器放入定时器链表 sixthmajor = register_chrdev(0, "buttons", &sixth_drv_ops);//注册驱动程序 if(sixthmajor < 0) printk("failes 1 buttons_drv register\n"); sixth_drv_class = class_create(THIS_MODULE, "buttons");//创建类 if(sixth_drv_class < 0) printk("failes 2 buttons_drv register\n"); sixth_drv_class_dev = class_device_create(sixth_drv_class, NULL, MKDEV(sixthmajor,0), NULL,"buttons");//创建设备节点 if(sixth_drv_class_dev < 0) printk("failes 3 buttons_drv register\n"); gpfcon = ioremap(0x56000050, 16);//重映射 gpfdat = gpfcon + 1; gpgcon = ioremap(0x56000060, 16);//重映射 gpgdat = gpgcon + 1; printk("register buttons_drv\n"); return 0;}static void sixth_drv_exit(void){ del_timer(&buttons_timer); unregister_chrdev(sixthmajor,"buttons"); class_device_unregister(sixth_drv_class_dev); class_destroy(sixth_drv_class); iounmap(gpfcon); iounmap(gpgcon); printk("unregister buttons_drv\n");}module_init(sixth_drv_init);module_exit(sixth_drv_exit);MODULE_LICENSE("GPL");

View Code

5、测试代码还是沿用sisth_test.c。将驱动程序和测试程序编译后的文件放入网络文件系统，测试发现不再出现抖动情况。具体过程参考

转载于:https://www.cnblogs.com/andyfly/p/9486304.html

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