From ffdb162ad4740e2da9dac924628bc2c6a2939060 Mon Sep 17 00:00:00 2001
From: Kristjan Komlosi <kristjan.komlosi@gmail.com>
Date: Sat, 2 Nov 2019 12:38:18 +0100
Subject: [PATCH] fixed a bug with negative uv values

---
 backend/sensors.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/backend/sensors.py b/backend/sensors.py
index bdfb83d..a979c85 100644
--- a/backend/sensors.py
+++ b/backend/sensors.py
@@ -206,14 +206,19 @@ class UVSensor:
         # scary computations ahead! refer to Vishay app note 84339 and Sparkfun
         # VEML6075 documentation.
 
-        # first, compensate for visible and IR noise
+        # compensate for visible and IR noise
         aCorr = aRaw - 2.22 * c1 - 1.33 * c2
         bCorr = bRaw - 2.95 * c1 - 1.74 * c2
 
-        # second, convert values into irradiances
-        a = aCorr * 0.00110
-        b = bCorr * 0.00125
+        # convert values into irradiances
+        a = aCorr * 1.06
+        b = bCorr * 0.48
 
+        # zero out negative results (readings with no uv)
+        if a < 0:
+            a = 0
+        if b < 0:
+            b = 0
         # last, calculate the UV index
         i = (a + b) / 2