PiClock project
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sht4x/sht4x.py
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261
sht4x/sht4x.py
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# SPDX-FileCopyrightText: Copyright (c) 2023 Jose D. Montoya
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#
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# SPDX-License-Identifier: MIT
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"""
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`sht4x`
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================================================================================
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MicroPython Driver fot the Sensirion Temperature and Humidity SHT40, SHT41 and SHT45 Sensor
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* Author: Jose D. Montoya
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"""
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import time
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import struct
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from micropython import const
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try:
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from typing import Tuple
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except ImportError:
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pass
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__version__ = "0.0.0+auto.0"
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__repo__ = "https://github.com/jposada202020/MicroPython_SHT4X.git"
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_RESET = const(0x94)
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HIGH_PRECISION = const(0)
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MEDIUM_PRECISION = const(1)
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LOW_PRECISION = const(2)
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temperature_precision_options = (HIGH_PRECISION, MEDIUM_PRECISION, LOW_PRECISION)
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temperature_precision_values = {
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HIGH_PRECISION: const(0xFD),
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MEDIUM_PRECISION: const(0xF6),
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LOW_PRECISION: const(0xE0),
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}
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HEATER200mW = const(0)
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HEATER110mW = const(1)
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HEATER20mW = const(2)
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heater_power_values = (HEATER200mW, HEATER110mW, HEATER20mW)
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TEMP_1 = const(0)
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TEMP_0_1 = const(1)
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heat_time_values = (TEMP_1, TEMP_0_1)
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wat_config = {
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HEATER200mW: (0x39, 0x32),
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HEATER110mW: (0x2F, 0x24),
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HEATER20mW: (0x1E, 0x15),
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}
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class SHT4X:
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"""Driver for the SHT4X Sensor connected over I2C.
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:param ~machine.I2C i2c: The I2C bus the SHT4X is connected to.
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:param int address: The I2C device address. Defaults to :const:`0x44`
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:raises RuntimeError: if the sensor is not found
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**Quickstart: Importing and using the device**
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Here is an example of using the :class:`SHT4X` class.
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First you will need to import the libraries to use the sensor
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.. code-block:: python
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from machine import Pin, I2C
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from micropython_sht4x import sht4x
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Once this is done you can define your `machine.I2C` object and define your sensor object
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.. code-block:: python
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i2c = I2C(1, sda=Pin(2), scl=Pin(3))
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sht = sht4x.SHT4X(i2c)
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Now you have access to the attributes
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.. code-block:: python
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temp = sht.temperature
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hum = sht.relative_humidity
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"""
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def __init__(self, i2c, address: int = 0x44) -> None:
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self._i2c = i2c
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self._address = address
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self._data = bytearray(6)
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self._command = 0xFD
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self._temperature_precision = HIGH_PRECISION
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self._heater_power = HEATER20mW
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self._heat_time = TEMP_0_1
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@property
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def temperature_precision(self) -> str:
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"""
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Sensor temperature_precision
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+------------------------------------+------------------+
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| Mode | Value |
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+====================================+==================+
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| :py:const:`sht4x.HIGH_PRECISION` | :py:const:`0` |
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+------------------------------------+------------------+
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| :py:const:`sht4x.MEDIUM_PRECISION` | :py:const:`1` |
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+------------------------------------+------------------+
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| :py:const:`sht4x.LOW_PRECISION` | :py:const:`2` |
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+------------------------------------+------------------+
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"""
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values = ("HIGH_PRECISION", "MEDIUM_PRECISION", "LOW_PRECISION")
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return values[self._temperature_precision]
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@temperature_precision.setter
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def temperature_precision(self, value: int) -> None:
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if value not in temperature_precision_values:
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raise ValueError("Value must be a valid temperature_precision setting")
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self._temperature_precision = value
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self._command = temperature_precision_values[value]
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@property
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def relative_humidity(self) -> float:
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"""
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The current relative humidity in % rH
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The RH conversion formula (1) allows values to be reported
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which are outside the range of 0 %RH … 100 %RH. Relative
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humidity values which are smaller than 0 %RH and larger than
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100 %RH are non-physical, however these “uncropped” values might
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be found beneficial in some cases (e.g. when the distribution of
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the sensors at the measurement boundaries are of interest)
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"""
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return self.measurements[1]
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@property
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def temperature(self) -> float:
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"""The current temperature in Celsius"""
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return self.measurements[0]
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@property
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def measurements(self) -> Tuple[float, float]:
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"""both `temperature` and `relative_humidity`, read simultaneously
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If you use t the heater function, sensor will be not give a response
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back. Waiting time is added to the logic to account for this situation
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"""
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self._i2c.writeto(self._address, bytes([self._command]), False)
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if self._command in (0x39, 0x2F, 0x1E):
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time.sleep(1.2)
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elif self._command in (0x32, 0x24, 0x15):
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time.sleep(0.2)
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time.sleep(0.2)
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self._i2c.readfrom_into(self._address, self._data)
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temperature, temp_crc, humidity, humidity_crc = struct.unpack_from(
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">HBHB", self._data
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)
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if temp_crc != self._crc(
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memoryview(self._data[0:2])
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) or humidity_crc != self._crc(memoryview(self._data[3:5])):
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raise RuntimeError("Invalid CRC calculated")
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temperature = -45.0 + 175.0 * temperature / 65535.0
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humidity = -6.0 + 125.0 * humidity / 65535.0
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humidity = max(min(humidity, 100), 0)
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return temperature, humidity
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@staticmethod
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def _crc(buffer) -> int:
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"""verify the crc8 checksum"""
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crc = 0xFF
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for byte in buffer:
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crc ^= byte
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for _ in range(8):
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if crc & 0x80:
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crc = (crc << 1) ^ 0x31
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else:
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crc = crc << 1
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return crc & 0xFF
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@property
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def heater_power(self) -> str:
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"""
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Sensor heater power
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The sensor has a heater. Three heating powers and two heating
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durations are selectable.
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The sensor executes the following procedure:
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1. The heater is enabled, and the timer starts its count-down.
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2. Measure is taken after time is up
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3. After the measurement is finished the heater is turned off.
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4. Temperature and humidity values are now available for readout.
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The maximum on-time of the heater commands is one second in order
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to prevent overheating
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+-------------------------------+---------------+
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| Mode | Value |
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+===============================+===============+
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| :py:const:`sht4x.HEATER200mW` | :py:const:`0` |
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+-------------------------------+---------------+
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| :py:const:`sht4x.HEATER110mW` | :py:const:`1` |
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+-------------------------------+---------------+
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| :py:const:`sht4x.HEATER20mW` | :py:const:`2` |
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+-------------------------------+---------------+
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"""
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values = ("HEATER200mW", "HEATER110mW", "HEATER20mW")
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return values[self._heater_power]
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@heater_power.setter
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def heater_power(self, value: int) -> None:
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if value not in heater_power_values:
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raise ValueError("Value must be a valid heater power setting")
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self._heater_power = value
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self._command = wat_config[value][self._heat_time]
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@property
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def heat_time(self) -> str:
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"""
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Sensor heat_time
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The sensor has a heater. Three heating powers and two heating
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durations are selectable.
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The sensor executes the following procedure:
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1. The heater is enabled, and the timer starts its count-down.
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2. Measure is taken after time is up
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3. After the measurement is finished the heater is turned off.
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4. Temperature and humidity values are now available for readout.
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The maximum on-time of the heater commands is one second in order
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to prevent overheating
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+----------------------------+---------------+
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| Mode | Value |
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+============================+===============+
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| :py:const:`sht4x.TEMP_1` | :py:const:`0` |
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+----------------------------+---------------+
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| :py:const:`sht4x.TEMP_0_1` | :py:const:`1` |
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+----------------------------+---------------+
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"""
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values = ("TEMP_1", "TEMP_0_1")
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return values[self._heat_time]
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@heat_time.setter
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def heat_time(self, value: int) -> None:
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if value not in heat_time_values:
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raise ValueError("Value must be a valid heat_time setting")
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self._heat_time = value
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self._command = wat_config[self._heater_power][value]
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def reset(self):
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"""
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Reset the sensor
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"""
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self._i2c.writeto(self._address, bytes([_RESET]), False)
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time.sleep(0.1)
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