From 07031f569ab75fb29c1c3bc1412442b6a55236f2 Mon Sep 17 00:00:00 2001
From: Felix Knecht <github@felixknecht.de>
Date: Tue, 17 Jan 2017 21:52:45 +0100
Subject: [PATCH] Correct bme280 code samples for negative values (#1735)

* Corrected examples for negative values

See issue #1734
Negative values need to be treated differently. Changed all the samples to reflect that

* Update bme280.md
---
 docs/en/modules/bme280.md | 42 ++++++++++++++++++++++++++++++++-------
 1 file changed, 35 insertions(+), 7 deletions(-)

diff --git a/docs/en/modules/bme280.md b/docs/en/modules/bme280.md
index 925369b0..212139b0 100644
--- a/docs/en/modules/bme280.md
+++ b/docs/en/modules/bme280.md
@@ -137,15 +137,27 @@ QNH = bme280.qfe2qnh(P, alt)
 print(string.format("QNH=%d.%03d", QNH/1000, QNH%1000))
 
 H, T = bme280.humi()
-print(string.format("T=%d.%02d", T/100, T%100))
+if T<0 then    
+  print(string.format("T=-%d.%02d", -T/100, -T%100))
+else
+  print(string.format("T=%d.%02d", T/100, T%100))
+end
 print(string.format("humidity=%d.%03d%%", H/1000, H%1000))
 D = bme280.dewpoint(H, T)
-print(string.format("dew_point=%d.%02d", D/100, D%100))
+if D<0 then
+  print(string.format("dew_point=-%d.%02d", -D/100, -D%100))
+else
+  print(string.format("dew_point=%d.%02d", D/100, D%100))
+end
 
 -- altimeter function - calculate altitude based on current sea level pressure (QNH) and measure pressure
 P = bme280.baro()
 curAlt = bme280.altitude(P, QNH)
-print(string.format("altitude=%d.%02d", curAlt/100, curAlt%100))
+if curAlt<0 then
+  print(string.format("altitude=-%d.%02d", -curAlt/100, -curAlt%100))
+else
+  print(string.format("altitude=%d.%02d", curAlt/100, curAlt%100))
+end
 ```
 
 Or simpler and more efficient
@@ -155,17 +167,29 @@ alt=320 -- altitude of the measurement place
 bme280.init(3, 4)
 
 T, P, H, QNH = bme280.read(alt)
-print(string.format("T=%d.%02d", T/100, T%100))
+if T<0 then
+  print(string.format("T=-%d.%02d", -T/100, -T%100))
+else
+  print(string.format("T=%d.%02d", T/100, T%100))
+end
 print(string.format("QFE=%d.%03d", P/1000, P%1000))
 print(string.format("QNH=%d.%03d", QNH/1000, QNH%1000))
 print(string.format("humidity=%d.%03d%%", H/1000, H%1000))
 D = bme280.dewpoint(H, T)
-print(string.format("dew_point=%d.%02d", D/100, D%100))
+if D<0 then
+  print(string.format("dew_point=-%d.%02d", -D/100, -D%100))
+else
+  print(string.format("dew_point=%d.%02d", D/100, D%100))
+end
 
 -- altimeter function - calculate altitude based on current sea level pressure (QNH) and measure pressure
 P = bme280.baro()
 curAlt = bme280.altitude(P, QNH)
-print(string.format("altitude=%d.%02d", curAlt/100, curAlt%100))
+if curAlt<0 then
+  print(string.format("altitude=-%d.%02d", -curAlt/100, -curAlt%100))
+else
+  print(string.format("altitude=%d.%02d", curAlt/100, curAlt%100))
+end
 ```
 
 Use `bme280.init(sda, scl, 1, 3, 0, 3, 0, 4)` for "game mode" - Oversampling settings  pressure ×4, temperature ×1, humidity ×0, sensor mode: normal mode, inactive duration  = 0.5 ms, IIR filter settings  filter coefficient 16.
@@ -175,7 +199,11 @@ Example of readout in forced mode (asynchronous)
 bme280.init(3, 4, nil, nil, nil, 0) -- initialize to sleep mode
 bme280.startreadout(0, function ()
   T, P = bme280.read()
-  print(string.format("T=%d.%02d", T/100, T%100))
+  if T<0 then
+    print(string.format("T=-%d.%02d", -T/100, -T%100))
+  else
+    print(string.format("T=%d.%02d", T/100, T%100))
+  end
 end)
 ```