temper.c

/*
 * Standalone temperature logger
 *
 */

#include <stdio.h>
#include <time.h>
#include "pcsensor.h"

/* Calibration adjustments */
/* See http://www.pitt-pladdy.com/blog/_20110824-191017_0100_TEMPer_under_Linux_perl_with_Cacti/ */
static float scale = 1.0287;
static float offset = -0.85;

int main(){
	int passes = 0;
	float tempc = 0.0000;
	do {
		usb_dev_handle* lvr_winusb = pcsensor_open();

		if (!lvr_winusb) {
			/* Open fails sometime, sleep and try again */
			sleep(3);
		}
		else {
	
			tempc = pcsensor_get_temperature(lvr_winusb);
			pcsensor_close(lvr_winusb);
		}
		++passes;
	}
	/* Read fails silently with a 0.0 return, so repeat until not zero
	   or until we have read the same zero value 3 times (just in case
	   temp is really dead on zero */
	while ((tempc > -0.0001 && tempc < 0.0001) || passes >= 4);

	if (!((tempc > -0.0001 && tempc < 0.0001) || passes >= 4)) {
		/* Apply calibrations */
		tempc = (tempc * scale) + offset;

		struct tm *utc;
		time_t t;
		t = time(NULL);
		utc = gmtime(&t);
		
		char dt[80];
		strftime(dt, 80, "%d-%b-%Y %H:%M", utc);

		printf("%s,%f\n", dt, tempc);
		fflush(stdout);

		return 0;
	}
	else {
		return 1;
	}

}