Update TC34725 color temp calculcation to catch divide by zero and return no value.

Author: tdicola

Adafruit_TCS34725/Adafruit_TCS34725.py

@@ -196,10 +196,18 @@ def calculateColorTemperature(rgb):
         Y = (-0.32466 * rgb['r']) + (1.57837 * rgb['g']) + (-0.73191 * rgb['b'])
         Z = (-0.68202 * rgb['r']) + (0.77073 * rgb['g']) + ( 0.56332 * rgb['b'])
 
+        # Check for divide by 0 (total darkness) and return None.
+        if (x + y + z) == 0:
+            return None
+
         # 2. Calculate the chromaticity co-ordinates
         xc = (X) / (X + Y + Z)
         yc = (Y) / (X + Y + Z)
 
+        # Check for divide by 0 again and return None.
+        if (0.1858 - yc) == 0:
+            return None
+
         # 3. Use McCamy's formula to determine the CCT
         n = (xc - 0.3320) / (0.1858 - yc)
 

Adafruit_TCS34725/Adafruit_TCS34725_Example.py

@@ -16,7 +16,10 @@
 colorTemp = tcs.calculateColorTemperature(rgb)
 lux = tcs.calculateLux(rgb)
 print rgb
-print "Color Temperature: %d K" % colorTemp
+if colorTemp is None:
+    print 'Too dark to determine color temperature!'
+else:
+    print "Color Temperature: %d K" % colorTemp
 print "Luminosity: %d lux" % lux
 tcs.setInterrupt(True)
 sleep(1)