树莓派3b驱动dht11温湿度传感器

Posted 2020-09-26

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

   

   可以看到湿度和温度值都正确的打印在了屏幕上。