From 655fdaefe8cf6cefffd431f3c0e7dff207eb08e1 Mon Sep 17 00:00:00 2001
From: mvn23 <schopdiedwaas@gmail.com>
Date: Tue, 30 Apr 2019 20:48:52 +0200
Subject: [PATCH] Fix negative lux value check.

Rewrite negative lux value check to avoid comparing unsigned long < 0.
---
 Adafruit_TSL2561_U.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/Adafruit_TSL2561_U.cpp b/Adafruit_TSL2561_U.cpp
index 231af5f..400fb05 100644
--- a/Adafruit_TSL2561_U.cpp
+++ b/Adafruit_TSL2561_U.cpp
@@ -443,10 +443,12 @@ uint32_t Adafruit_TSL2561_Unified::calculateLux(uint16_t broadband, uint16_t ir)
 #endif
 
   unsigned long temp;
-  temp = ((channel0 * b) - (channel1 * m));
-
+  channel0 = channel0 * b;
+  channel1 = channel1 * m;
+  
+  temp = 0;
   /* Do not allow negative lux value */
-  if (temp < 0) temp = 0;
+  if (channel0 > channel1) temp = channel0 - channel1;
 
   /* Round lsb (2^(LUX_SCALE-1)) */
   temp += (1 << (TSL2561_LUX_LUXSCALE-1));