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Adafruit_SHT31.py
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Adafruit_SHT31.py
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# Copyright (c) 2014 Adafruit Industries
# Author: Tony DiCola
#
# Based on the BME280 driver with SHT31D changes provided by
# Ralf Mueller, Erfurt
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import logging
import time
# SHT31D default address.
SHT31_I2CADDR = 0x44
# SHT31D Registers
SHT31_MEAS_HIGHREP_STRETCH = 0x2C06
SHT31_MEAS_MEDREP_STRETCH = 0x2C0D
SHT31_MEAS_LOWREP_STRETCH = 0x2C10
SHT31_MEAS_HIGHREP = 0x2400
SHT31_MEAS_MEDREP = 0x240B
SHT31_MEAS_LOWREP = 0x2416
SHT31_READSTATUS = 0xF32D
SHT31_CLEARSTATUS = 0x3041
SHT31_SOFTRESET = 0x30A2
SHT31_HEATER_ON = 0x306D
SHT31_HEATER_OFF = 0x3066
SHT31_STATUS_DATA_CRC_ERROR = 0x0001
SHT31_STATUS_COMMAND_ERROR = 0x0002
SHT31_STATUS_RESET_DETECTED = 0x0010
SHT31_STATUS_TEMPERATURE_ALERT = 0x0400
SHT31_STATUS_HUMIDITY_ALERT = 0x0800
SHT31_STATUS_HEATER_ACTIVE = 0x2000
SHT31_STATUS_ALERT_PENDING = 0x8000
class SHT31(object):
def __init__(self, address=SHT31_I2CADDR, i2c=None,
**kwargs):
self._logger = logging.getLogger('Adafruit_SHT.SHT31D')
# Create I2C device.
if i2c is None:
import Adafruit_GPIO.I2C as I2C
i2c = I2C
self._device = i2c.get_i2c_device(address, **kwargs)
time.sleep(0.05) # Wait the required time
def _writeCommand(self, cmd):
self._device.write8(cmd >> 8, cmd & 0xFF)
def reset(self):
self._writeCommand(SHT31_SOFTRESET)
time.sleep(0.01) # Wait the required time
def clear_status(self):
self._writeCommand(SHT31_CLEARSTATUS);
def read_status(self):
self._writeCommand(SHT31_READSTATUS);
buffer = self._device.readList(0, 3)
stat = buffer[0] << 8 | buffer[1]
if buffer[2] != self._crc8(buffer[0:2]):
return None
return stat
def is_data_crc_error(self):
return bool(self.read_status() & SHT31_STATUS_DATA_CRC_ERROR)
def is_command_error(self):
return bool(self.read_status() & SHT31_STATUS_COMMAND_ERROR)
def is_reset_detected(self):
return bool(self.read_status() & SHT31_STATUS_RESET_DETECTED)
def is_tracking_temperature_alert(self):
return bool(self.read_status() & SHT31_STATUS_TEMPERATURE_ALERT)
def is_tracking_humidity_alert(self):
return bool(self.read_status() & SHT31_STATUS_HUMIDITY_ALERT)
def is_heater_active(self):
return bool(self.read_status() & SHT31_STATUS_HEATER_ACTIVE)
def is_alert_pending(self):
return bool(self.read_status() & SHT31_STATUS_ALERT_PENDING)
def set_heater(self, doEnable = True):
if doEnable:
self._writeCommand(SHT31_HEATER_ON)
else:
self._writeCommand(SHT31_HEATER_OFF)
def read_temperature_humidity(self):
self._writeCommand(SHT31_MEAS_HIGHREP)
time.sleep(0.015)
buffer = self._device.readList(0, 6)
if buffer[2] != self._crc8(buffer[0:2]):
return (float("nan"), float("nan"))
rawTemperature = buffer[0] << 8 | buffer[1]
temperature = 175.0 * rawTemperature / 0xFFFF - 45.0
if buffer[5] != self._crc8(buffer[3:5]):
return (float("nan"), float("nan"))
rawHumidity = buffer[3] << 8 | buffer[4]
humidity = 100.0 * rawHumidity / 0xFFFF
return (temperature, humidity)
def read_temperature(self):
(temperature, humidity) = self.read_temperature_humidity()
return temperature
def read_humidity(self):
(temperature, humidity) = self.read_temperature_humidity()
return humidity
def _crc8(self, buffer):
""" Polynomial 0x31 (x8 + x5 +x4 +1) """
polynomial = 0x31;
crc = 0xFF;
index = 0
for index in range(0, len(buffer)):
crc ^= buffer[index]
for i in range(8, 0, -1):
if crc & 0x80:
crc = (crc << 1) ^ polynomial
else:
crc = (crc << 1)
return crc & 0xFF