ds18b20/temp.c

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

#define N  2

float getTempByDev(char *devName);
void *run(void *args);

float results[N];
pthread_t tids[N];
char *names[] = {"/dev/ds18b20-223","/dev/ds18b20-224"};

int main(int argc, char *argv[])
{
    int i = 0;
    for (i = 0; i < N; i++)
    {
        pthread_create(&tids[i], NULL, run, (void*)i);
    }
    for (i = 0; i < N; i++)
    {
        pthread_join(tids[i], NULL);
    }
    for (i = 0; i < N; i++)
    {
        if (i > 0)
        {
            printf("#");
        }
        printf("%.3f", results[i]);
    }
    printf("\n");
    return 0; 
}

void *run(void *args)
{
    int ret=(int)args;
    float res = getTempByDev(names[ret]);
    results[ret] = res;
}

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;
    short count = 0;

    fd = open(devName, 0);  
    if (fd >= 0) 
    {
        do
        {
            count++;
            int i = read(fd, &result, sizeof(&result));
            if (i >= 0)
            {
                hightBitValue = result[1];
                lowBitValue = result[0];
                hightBitValue <<= 8;
                hightBitValue = hightBitValue + lowBitValue;
                if ((result[1] & 0xf8))
                {
                    hightBitValue = ~hightBitValue + 1;
                    value = hightBitValue * p * -1;
                }
                else
                {
                    value = hightBitValue * p;
                }
            }
        }
        while ((value < -55 || value > 125) && count < 5);  
        close(fd);
    }
    return value;
}