驱动-----dht11温湿度传感器

单总线：只用一根线。

复位信号：设置为输出模式，低电平20ms，然后再拉高30us。然后设置为输入模式，dht11会先拉低80us，然后拉高80us表示对接成功

数据0：开始先拉低50us，然后拉高26~28us表示0

数据1：开始拉低50us,然后拉高70us表示1

每传输一位的数据都要间隔一个拉低50us

梳理一下时序：

应用程序：

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <asm/io.h>
#include <asm/string.h>
#include <asm/uaccess.h>
#include <linux/miscdevice.h>
#include <asm-generic/errno-base.h>
#include <mach/gpio-nrs.h>
#include <mach/gpio.h>
#include <linux/delay.h>#define DEV_NAME "dht11"
#define PIN_DHT11 S3C2410_GPF(6)static void dht11_start(void)
{gpio_request(PIN_DHT11, "pin_dht11");gpio_direction_output(PIN_DHT11, 1);msleep(40);gpio_set_value(PIN_DHT11, 0);mdelay(18);gpio_set_value(PIN_DHT11, 1);udelay(30);gpio_direction_input(PIN_DHT11);
}static int dht11_wait_respon(void)
{int time = 100;while((time > 0) && gpio_get_value(PIN_DHT11)){udelay(1);time--;}if(time <= 0){printk("dht11_wait_respon   1\n");return -1;}time = 100;while((time > 0) && (!gpio_get_value(PIN_DHT11))){udelay(1);time--;}if(time <= 0){printk("dht11_wait_respon   2\n");return -1;}time = 100;while((time > 0) && gpio_get_value(PIN_DHT11)){udelay(1);time--;}if(time <= 0){printk("dht11_wait_respon   3\n");return -1;}return 0;
}static int get_bit(void)
{int time = 100;while((time > 0) && (!gpio_get_value(PIN_DHT11))){udelay(1);time--;}if(time <= 0){printk("get_bit   1\n");return -1;}udelay(30);if(0 == gpio_get_value(PIN_DHT11))return 0;time = 100;while((time > 0) && gpio_get_value(PIN_DHT11)){udelay(1);time--;}if(time <= 0){printk("get_bit   2\n");return -1;}return 1;
}static int dht11_get_data(unsigned char * data)
{int i = 0;int j = 0;for(j = 0; j < 5; j++){for(i = 0; i < 8; i++){char tmp = 0;data[j] <<= 1;tmp = get_bit();	if(tmp < 0)return -1;data[j] |= tmp;}}return 0;
}static int open (struct inode * inode, struct file * file)
{printk("dht11 open ...\n");return 0;
}static ssize_t read (struct file * file, char __user * buf, size_t len, loff_t * offset)
{int ret = 0;unsigned char data[5] = {0};dht11_start();ret = dht11_wait_respon();if(ret < 0)return -1;ret = dht11_get_data(data);if(ret < 0)return -1;copy_to_user(buf, data, sizeof(data));printk("dht11 read ...\n");return 0;
}static ssize_t write (struct file * file, const char __user * buf, size_t len, loff_t * offset)
{return 0;
}static int close (struct inode * inode, struct file * file)
{printk("dht11 close ...\n");return 0;
}static struct file_operations fops = 
{.owner = THIS_MODULE,.open = open,.read = read,.write = write,.release = close
};static struct miscdevice misc = 
{.minor = MISC_DYNAMIC_MINOR,.name = DEV_NAME,.fops = &fops
};static int __init dht11_init(void)
{int ret = misc_register(&misc);if(ret < 0)goto err_misc_register;printk("dht11_init  ...\n");return ret;err_misc_register:misc_deregister(&misc);printk("dht11 misc_register faidht11\n");	return ret;
}static void __exit dht11_exit(void)
{misc_deregister(&misc);printk("dht11_exit  ###############################\n");
}module_init(dht11_init);
module_exit(dht11_exit);
MODULE_LICENSE("GPL");