树莓派3b驱动dht11温湿度传感器

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  1. 新建并打开C文件

    touch dht11.c

    sudo vim dht11.c

  2. 编写驱动程序

     

     1 #include<wiringPi.h>
     2 #include<stdio.h>
     3 #include<stdlib.h>
     4 #include<stdint.h>
     5 #define MAX_TIME 85
     6 #define DHT11PIN 7
     7 #define ATTEMPTS 5                 //retry 5 times when no response
     8 int dht11_val[5]={0,0,0,0,0};
     9 
    10 int dht11_read_val(){
    11     uint8_t lststate=HIGH;         //last state
    12     uint8_t counter=0;
    13     uint8_t j=0,i;
    14     for(i=0;i<5;i++)
    15         dht11_val[i]=0;
    16 
    17     //host send start signal    
    18     pinMode(DHT11PIN,OUTPUT);      //set pin to output 
    19     digitalWrite(DHT11PIN,LOW);    //set to low at least 18ms 
    20     delay(18);
    21     digitalWrite(DHT11PIN,HIGH);   //set to high 20-40us
    22     delayMicroseconds(40);
    23 
    24     //start recieve dht response
    25     pinMode(DHT11PIN,INPUT);       //set pin to input
    26     for(i=0;i<MAX_TIME;i++)         
    27     {
    28         counter=0;
    29         while(digitalRead(DHT11PIN)==lststate){     //read pin state to see if dht responsed. if dht always high for 255 + 1 times, break this while circle
    30             counter++;
    31             delayMicroseconds(1);
    32             if(counter==255)
    33                 break;
    34         }
    35         lststate=digitalRead(DHT11PIN);    //read current state and store as last state. 
    36         if(counter==255)   //if dht always high for 255 + 1 times, break this for circle
    37             break;
    38  // top 3 transistions are ignored, maybe aim to wait for dht finish response signal
    39         if((i>=4)&&(i%2==0)){
    40             dht11_val[j/8]<<=1;     //write 1 bit to 0 by moving left (auto add 0)
    41             if(counter>16)      //long mean 1
    42                 dht11_val[j/8]|=1;     //write 1 bit to 1 
    43             j++;
    44         }
    45     }
    46     // verify checksum and print the verified data
    47     if((j>=40)&&(dht11_val[4]==((dht11_val[0]+dht11_val[1]+dht11_val[2]+dht11_val[3])& 0xFF))){
    48         printf("RH:%d,TEMP:%d\\n",dht11_val[0],dht11_val[2]);
    49         return 1;
    50     }
    51     else
    52         return 0;
    53 }
    54 
    55 int main(void){
    56     int attempts=ATTEMPTS;
    57     if(wiringPiSetup()==-1)
    58         exit(1);
    59     while(attempts){                        //you have 5 times to retry
    60         int success = dht11_read_val();     //get result including printing out
    61         if (success) {                      //if get result, quit program; if not, retry 5 times then quit
    62             break;
    63         }
    64         attempts--;
    65         delay(2500);  
    66   }
    67     return 0;
    68 }

     

    按esc,然后输入:wq保存退出。 

  3. 编译c文件

    需安装wiringPi开发库,安装教程详见本博主博客:树莓派安装wiringPi开发库

    输入命令:

     

    gcc -Wall -o dht11 dht11.c -lwiringPi

    1

    gcc是编译器,-Wall是在编译时显示警告信息,-o dht11.c是将dht11.c文件编译成文件名为dht11的可执行文件,-lwiringPi是将wiringPi头文件包含在可执行文件中。

     

  4. 运行程序

    输入命令:

    sudo ./dht11

    技术分享

    可以看到湿度和温度值都正确的打印在了屏幕上。

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