Retry loop added; Formatted datetime added to output; Calibration met…

…hod added;

temper.c

@@ -3,23 +3,56 @@
  *
  */
 
+#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);
 
-	usb_dev_handle* lvr_winusb = pcsensor_open();
+	if (!((tempc > -0.0001 && tempc < 0.0001) || passes >= 4)) {
+		/* Apply calibrations */
+		tempc = (tempc * scale) + offset;
 
-	if (!lvr_winusb) {
-		printf("NaN");
+		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 -1;
+		return 0;
+	}
+	else {
+		return 1;
 	}
 
-	float tempc = pcsensor_get_temperature(lvr_winusb);
-	pcsensor_close(lvr_winusb);
-	printf("%f", tempc);
-	fflush(stdout);
-
-	return 0;
 }