ds18b20/gettemp.c

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/select.h>

float getTempByDev(char *devName);

int main(int argc, char *argv[])
{
    if (argc == 2)
    {
        char * ch = argv[1];
        //        int gpio = atoi(ch);
        char * name = "/dev/ds18b20-";
        char devName[16];
        strcpy(devName, name);
        strcat(devName, ch);
        float t223 = getTempByDev(devName);
        printf("%.4f", t223);
    }
    else
    {
        printf("-1");
    }
    return 0; 
}

float getTempByDev(char *devName)
{
    int fd;  
    unsigned char result[2] = {0};  
    unsigned int hightBitValue = 0;  
    unsigned int lowBitValue = 0;  
    float p = 0.0625;
    float value = 1024.0f;

    fd = open(devName, 0);  
    if (fd >= 0) 
    {
        int i = read(fd, &result, sizeof(&result));
        if (i >= 0)
        {
            //        printf("%xH-%xH\n", result[1], result[0]);
            hightBitValue = result[1];
            lowBitValue = result[0];
            hightBitValue <<= 8;
            hightBitValue = hightBitValue + lowBitValue;
            if ((result[1] & 0xf8))
            {
                //                printf("aaa\n");
                hightBitValue = ~hightBitValue + 1;
                value = hightBitValue * p * -1;
            }
            else
            {
                value = hightBitValue * p;
            }

        }  
        close(fd);
    }
    return value;
}