树莓派ds18b20探测温度

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <dirent.h>
#include <unistd.h>
#include <stdlib.h>



int ds18b20_get_temperature(float *temp)

{
    int     fd=-1;
    char    buf[256];                       //创建一个buf
    DIR*    dir;                            //用opendir打开文件夹，返回一个指针
    struct  dirent *ptr;                  //定义一个指向文件夹信息结构体的指针fp，
    char*   l ="28-";
    char*   m ="t=";    
    char*   q;  
    char    strtemp[20];
    int     found;                           //是否找到设备ds18b20，找到found=1，没找到found=0
    char    path[128]="/sys/bus/w1/devices/";//用来存放目录路径
    char*   point;


    dir =opendir(path);                    //打开设备所在路径文件夹



 /*判断传进来的地址是否存在，不存在返回-1*/
   if(temp==NULL)
   {
     return -1;
   }


 /*判断设备所在路径是否合法，合法则打印路径，不合法则调用系统出错,并返回-2 */
   if (dir==NULL)
    {
      perror("oepn devicedir failure");
      return -2;
    }
   else
    printf("\nopendir succful!\n") ;





   /*读取产品序列号，即：读取28-后的字符串*/

   ptr=readdir(dir);

   if((ptr=readdir(dir)) == NULL)
   {
     perror("ptr=readdir(dir)");
     return -1;
   }

   while((ptr=readdir(dir)) !=NULL)
   {

      //printf("d_name : %s\n",strstr(ptr->d_name,l));

      q=strstr(ptr->d_name,l);                //指针q指向（传感设备文件全名字符串）：“28-041731f7c0ff”

      if(q!=NULL)                                //如果指针不指向空

    {

       strcpy(strtemp,ptr->d_name);           //把设备名拷贝到数组strtemp中去 
       printf("DEVICE:%s\n",strtemp);
       printf("DS18b20 SN=%s\n",q+strlen(l)); //打印去头（28-）产品序列号
       printf("path=%s\n",path);

       strncat(path,strtemp,sizeof(strtemp));
       strncat(path,"/w1_slave",sizeof("/w1_slave"));
       printf("ALL_path:%s\n",path);



     if((fd=open(path,O_RDONLY))<0)
     {
        perror("open2 error:");
        return -4;
     }
     else
     {
        printf("fd=%d\n",fd);
     }

     memset(buf,0,sizeof(buf));
     lseek(fd,0,SEEK_SET);

     if (  (read(fd,buf,sizeof(buf)) )<0  )
      {
       perror("read error\n");
       return -5;
      }


     strstr(buf,"t=");
     printf("data=%s\n",buf);


     point=strstr(buf,m);

     printf("t=%s",point+strlen(m));

    if(!point)
     {
      perror("can't not get [T]");
      return -6;

     }

   *temp=atof(point+strlen(m))/1000;

     }
    }
}






int main(int argc,char**argv)
{
    float temp;  //温度是浮点数

     if(ds18b20_get_temperature(&temp)<0)
    {
        printf("ds18b20 Initialization failed\n");
        return 1;
    }

    else
    {
        printf("The real time temperatue is %f°C\n",temp);

    }
    return 0;
}

运行结果：

opendir succful!
DEVICE:28-041731f7c0ff
DS18b20 SN=041731f7c0ff
path=/sys/bus/w1/devices/
ALL_path:/sys/bus/w1/devices/28-041731f7c0ff/w1_slave
fd=4
data=d6 01 4b 46 7f ff 0c 10 e9 : crc=e9 YES
d6 01 4b 46 7f ff 0c 10 e9 t=29375

t=29375
The real time temperatue is 29.375000°C