How do you write a C program that reads the temperature of a

How do you write a C program that reads the temperature of a sensor?

Solution

#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>

int main (void) {
DIR *dir;
struct dirent *dirent;
char dev[16]; // Dev ID
char devPath[128]; // Path to device
char buf[256]; // Data from device
char tmpData[6]; // Temp C * 1000 reported by device
char path[] = \"/sys/bus/w1/devices\";
ssize_t numRead;

dir = opendir (path);
if (dir != NULL)
{
while ((dirent = readdir (dir)))
// 1-wire devices are links beginning with 28-
if (dirent->d_type == DT_LNK &&
strstr(dirent->d_name, \"28-\") != NULL) {
strcpy(dev, dirent->d_name);
printf(\"\ Device: %s\ \", dev);
}
(void) closedir (dir);
}
else
{
perror (\"Couldn\'t open the w1 devices directory\");
return 1;
}

// Assemble path to OneWire device
sprintf(devPath, \"%s/%s/w1_slave\", path, dev);
// Read temp continuously
// Opening the device\'s file triggers new reading
while(1) {
int fd = open(devPath, O_RDONLY);
if(fd == -1)
{
perror (\"Couldn\'t open the w1 device.\");
return 1;
}
while((numRead = read(fd, buf, 256)) > 0)
{
strncpy(tmpData, strstr(buf, \"t=\") + 2, 5);
float tempC = strtof(tmpData, NULL);
printf(\"Device: %s - \", dev);
printf(\"Temp: %.3f C \", tempC / 1000);
printf(\"%.3f F\ \ \", (tempC / 1000) * 9 / 5 + 32);
}
close(fd);
}
/* return 0; --never called due to loop */
}