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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

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2046e8e
fix DHT22 handling of negative temperatures
jerryneedell Apr 28, 2018
c8dbbdb
fix typo
jerryneedell Apr 28, 2018
2aaaf1b
fix pylint issue
jerryneedell Apr 28, 2018
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15 changes: 10 additions & 5 deletions adafruit_dht.py
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Original file line number Diff line number Diff line change
Expand Up @@ -148,18 +148,24 @@ def measure(self):
for byte_start in range(0, 80, 16):
buf.append(self._pulses_to_binary(pulses, byte_start, byte_start+16))

# humidity is 2 bytes
if self._dht11:
# humidity is 1 byte
self._humidity = buf[0]
else:
# humidity is 2 bytes
self._humidity = ((buf[0]<<8) | buf[1]) / 10

# temperature is 2 bytes
if self._dht11:
# temperature is 1 byte
self._temperature = buf[2]
else:
self._temperature = ((buf[2]<<8) | buf[3]) / 10

# temperature is 2 bytes
# MSB is sign, bits 0-14 are magnitude)
raw_temperature = (((buf[2] & 0x7f)<<8) | buf[3]) / 10
# set sign
if buf[2] & 0x80:
raw_temperature = -raw_temperature
self._temperature = raw_temperature
# calc checksum
chk_sum = 0
for b in buf[0:4]:
Expand All @@ -170,7 +176,6 @@ def measure(self):
# check sum failed to validate
raise RuntimeError("Checksum did not validate. Try again.")


else:
raise RuntimeError("A full buffer was not returned. Try again.")

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