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fix DHT22 handling of negative temperatures #10

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Merged
merged 3 commits into from
Apr 29, 2018
Merged

fix DHT22 handling of negative temperatures #10

merged 3 commits into from
Apr 29, 2018

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jerryneedell
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modified driver to correctly handle sign bit for the DHT22.

tested in freezer - dht_simpletest converts to F so the transition was failing at 32 F. see issue #9

 Temp: 33.8 F Humidity: 18.6% 
Temp: 33.6 F Humidity: 18.8% 
Temp: 33.3 F Humidity: 18.9% 
Temp: 33.1 F Humidity: 19.0% 
Temp: 32.9 F Humidity: 19.2% 
Temp: 32.5 F Humidity: 19.3% 
Temp: 32.4 F Humidity: 19.4% 
Temp: 32.0 F Humidity: 19.5% 
Temp: 31.8 F Humidity: 19.7% 
Temp: 31.6 F Humidity: 19.8% 
Temp: 31.5 F Humidity: 20.0%

Note - tested DHT11 in the freezer, but it never reported any value < 1 C - according to the data sheet, its range is 0- 50 C so there is no need for a sign bit.

@jerryneedell jerryneedell requested a review from mrmcwethy April 28, 2018 21:17
mrmcwethy
mrmcwethy approved these changes Apr 29, 2018
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I like what you did. I should have found this, but did not try the freezer test.

@dhalbert dhalbert merged commit a384b7d into adafruit:master Apr 29, 2018
@jerryneedell jerryneedell mentioned this pull request Apr 29, 2018
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tannewt pushed a commit to adafruit/Adafruit_CircuitPython_Bundle that referenced this pull request Apr 30, 2018
@adafruit-adabot
Automated update by Adabot (adafruit/adabot@86a73b0)
fda89dc 
Updating https://github.com/adafruit/Adafruit_CircuitPython_DHT to 3.1.0 from 3.0.1:
  > Merge pull request adafruit/Adafruit_CircuitPython_DHT#10 from jerryneedell/jerryn_negative
  > Merge pull request adafruit/Adafruit_CircuitPython_DHT#8 from jerryneedell/jerryn_dht
  > Merge pull request adafruit/Adafruit_CircuitPython_DHT#6 from sommersoft/new_docs
  > Merge pull request adafruit/Adafruit_CircuitPython_DHT#5 from sommersoft/new_docs
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@jerryneedell @mrmcwethy @dhalbert