人体红外传感器SR501

6ull上使用GPIO4_19，具体模块说明可以查看《03_i.MX.6ULL裸机开发手册_V1.0》。

感应到人体并输出高电平后，延时时间一结束，输出将自动从高电平变为低电平
感应到人体后输出高电平后，在延时时间段内，如果有人体在其感应范围内活动，其输出将一直保持高电平，直到人离开后才延时将高电平变为低电平

编程

定义gpio：

/* gpio描述结构体 */
struct gpio_desc{
    int gpio;   //引脚编号
    int irq;    //中断号
    char *name; //名字
    int key;    //按键值
    struct timer_list key_timer;    //定时器，用于消除抖动
} ;

static struct gpio_desc gpios[2] = {
    {115, 0, "sr501", 1,},      //GPIO4_19
    //{132, 0, "gpio_100ask_2", 2,},
};

入口函数：对每个gpio申请中断，注册字符设备的file_operations，创建设备节点

/* 在入口函数 */
static int __init gpio_drv_init(void)
{
    int err;
    int i;
    int count = sizeof(gpios)/sizeof(gpios[0]);
    
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    
    for (i = 0; i < count; i++)
    {       
        gpios[i].irq  = gpio_to_irq(gpios[i].gpio); //把引脚号转换为中断号,

        //注册中断，处理函数为gpio_key_isr(gpios[i].irq, &gpios[i])
        err = request_irq(gpios[i].irq, gpio_key_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
                         gpios[i].name, &gpios[i]);
    }

    /* 注册file_operations    */
    major = register_chrdev(0, "100ask_gpio_key", &gpio_key_drv);  /* /dev/gpio_desc */

    gpio_class = class_create(THIS_MODULE, "100ask_gpio_key_class");
    if (IS_ERR(gpio_class)) {
        printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
        unregister_chrdev(major, "100ask_gpio_key");
        return PTR_ERR(gpio_class);
    }

    device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "sr105"); /* /dev/sr105 */
    
    return err;
}

出口函数：

static void __exit gpio_drv_exit(void)
{
    int i;
    int count = sizeof(gpios)/sizeof(gpios[0]);
    
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);

    device_destroy(gpio_class, MKDEV(major, 0));
    class_destroy(gpio_class);
    unregister_chrdev(major, "100ask_gpio_key");

    for (i = 0; i < count; i++)
    {
        free_irq(gpios[i].irq, &gpios[i]);
    }
}

在gpio中断处理函数中，进行sr501电平值的读取

static irqreturn_t gpio_key_isr(int irq, void *dev_id)
{
    struct gpio_desc *gpio_desc = dev_id;
    int val;
    int key;


    printk("gpio_key_isr key %d irq happened\n", gpio_desc->gpio);
    val = gpio_get_value(gpio_desc->gpio);


    //printk("key_timer_expire key %d %d\n", gpio_desc->gpio, val);
    key = (gpio_desc->key) | (val<<8);
    put_key(key);
    wake_up_interruptible(&gpio_wait);
    kill_fasync(&button_fasync, SIGIO, POLL_IN);
    
    return IRQ_HANDLED;
}

修改file_operations结构体及其函数：gpio_drv_read函数中返回ringbuf中的值

static DECLARE_WAIT_QUEUE_HEAD(gpio_wait);
/* 实现对应的open/read/write等函数，填入file_operations结构体                   */
static ssize_t gpio_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset)
{
    //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    int err;
    int key;

    if (is_key_buf_empty() && (file->f_flags & O_NONBLOCK))
        return -EAGAIN;
    
    wait_event_interruptible(gpio_wait, !is_key_buf_empty());
    key = get_key();
    err = copy_to_user(buf, &key, 4);
    
    return 4;
}
...
/* 定义自己的file_operations结构体                                              */
static struct file_operations gpio_key_drv = {
    .owner   = THIS_MODULE,
    .read    = gpio_drv_read,
    .poll    = gpio_drv_poll,
    .fasync  = gpio_drv_fasync,
};

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