Working code library for SHT4x

README.rst

@@ -33,11 +33,6 @@ This is easily achieved by downloading
 
 Installing from PyPI
 =====================
-.. note:: This library is not available on PyPI yet. Install documentation is included
-   as a standard element. Stay tuned for PyPI availability!
-
-.. todo:: Remove the above note if PyPI version is/will be available at time of release.
-   If the library is not planned for PyPI, remove the entire 'Installing from PyPI' section.
 
 On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally `from
 PyPI <https://pypi.org/project/adafruit-circuitpython-sht4x/>`_. To install for current user:
@@ -64,7 +59,29 @@ To install in a virtual environment in your current project:
 Usage Example
 =============
 
-.. todo:: Add a quick, simple example. It and other examples should live in the examples folder and be included in docs/examples.rst.
+.. code-block:: python
+
+    import time
+    import busio
+    import board
+    import adafruit_sht4x
+
+    i2c = busio.I2C(board.SCL, board.SDA)
+    sht = adafruit_sht4x.SHT4x(i2c)
+    print("Found SHT4x with serial number", hex(sht.serial_number))
+
+    sht.mode = adafruit_sht4x.Mode.NOHEAT_HIGHPRECISION
+    # Can also set the mode to enable heater
+    # sht.mode = adafruit_sht4x.Mode.LOWHEAT_100MS
+    print("Current mode is: ", adafruit_sht4x.Mode.string[sht.mode])
+
+    while True:
+        temperature, relative_humidity = sht.measurements
+        print("Temperature: %0.1f C" % temperature)
+        print("Humidity: %0.1f %%" % relative_humidity)
+        print("")
+        time.sleep(1)
+
 
 Contributing
 ============

adafruit_sht4x.py

@@ -26,7 +26,177 @@
 
 """
 
-# imports
+import time
+import struct
+import adafruit_bus_device.i2c_device as i2c_device
+from micropython import const
 
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_SHT4x.git"
+
+
+_SHT4X_DEFAULT_ADDR = const(0x44)  # SHT4X I2C Address
+_SHT4X_READSERIAL = const(0x89)  # Read Out of Serial Register
+_SHT4X_SOFTRESET = const(0x94)  # Soft Reset
+
+
+class CV:
+    """struct helper"""
+
+    @classmethod
+    def add_values(cls, value_tuples):
+        """Add CV values to the class"""
+        cls.string = {}
+        cls.delay = {}
+
+        for value_tuple in value_tuples:
+            name, value, string, delay = value_tuple
+            setattr(cls, name, value)
+            cls.string[value] = string
+            cls.delay[value] = delay
+
+    @classmethod
+    def is_valid(cls, value):
+        """Validate that a given value is a member"""
+        return value in cls.string
+
+
+class Mode(CV):
+    """Options for ``power_mode``"""
+
+    pass  # pylint: disable=unnecessary-pass
+
+
+Mode.add_values(
+    (
+        ("NOHEAT_HIGHPRECISION", 0xFD, "No heater, high precision", 0.01),
+        ("NOHEAT_MEDPRECISION", 0xF6, "No heater, med precision", 0.005),
+        ("NOHEAT_LOWPRECISION", 0xE0, "No heater, low precision", 0.002),
+        ("HIGHHEAT_1S", 0x39, "High heat, 1 second", 1.1),
+        ("HIGHHEAT_100MS", 0x32, "High heat, 0.1 second", 0.11),
+        ("MEDHEAT_1S", 0x2F, "Med heat, 1 second", 1.1),
+        ("MEDHEAT_100MS", 0x24, "Med heat, 0.1 second", 0.11),
+        ("LOWHEAT_1S", 0x1E, "Low heat, 1 second", 1.1),
+        ("LOWHEAT_100MS", 0x15, "Low heat, 0.1 second", 0.11),
+    )
+)
+
+
+class SHT4x:
+    """
+    A driver for the SHT4x temperature and humidity sensor.
+
+    :param ~busio.I2C i2c_bus: The `busio.I2C` object to use. This is the only required parameter.
+
+    """
+
+    def __init__(self, i2c_bus):
+        self.i2c_device = i2c_device.I2CDevice(i2c_bus, _SHT4X_DEFAULT_ADDR)
+        self._buffer = bytearray(6)
+        self.reset()
+        self._mode = Mode.NOHEAT_HIGHPRECISION  # pylint: disable=no-member
+
+    @property
+    def serial_number(self):
+        """The unique 32-bit serial number"""
+        self._buffer[0] = _SHT4X_READSERIAL
+        with self.i2c_device as i2c:
+            i2c.write(self._buffer, end=1)
+            time.sleep(0.01)
+            i2c.readinto(self._buffer)
+
+        ser1 = self._buffer[0:2]
+        ser1_crc = self._buffer[2]
+        ser2 = self._buffer[3:5]
+        ser2_crc = self._buffer[5]
+
+        # check CRC of bytes
+        if ser1_crc != self._crc8(ser1) or ser2_crc != self._crc8(ser2):
+            raise RuntimeError("Invalid CRC calculated")
+
+        serial = (ser1[0] << 24) + (ser1[1] << 16) + (ser2[0] << 8) + ser2[1]
+        return serial
+
+    def reset(self):
+        """Perform a soft reset of the sensor, resetting all settings to their power-on defaults"""
+        self._buffer[0] = _SHT4X_SOFTRESET
+        with self.i2c_device as i2c:
+            i2c.write(self._buffer, end=1)
+        time.sleep(0.001)
+
+    @property
+    def mode(self):
+        """The current sensor reading mode (heater and precision)"""
+        return self._mode
+
+    @mode.setter
+    def mode(self, new_mode):
+        print(new_mode)
+        if not Mode.is_valid(new_mode):
+            raise AttributeError("mode must be a Mode")
+        self._mode = new_mode
+
+    @property
+    def relative_humidity(self):
+        """The current relative humidity in % rH"""
+        return self.measurements[1]
+
+    @property
+    def temperature(self):
+        """The current temperature in degrees celsius"""
+        return self.measurements[0]
+
+    @property
+    def measurements(self):
+        """both `temperature` and `relative_humidity`, read simultaneously"""
+
+        temperature = None
+        humidity = None
+        command = self._mode
+
+        with self.i2c_device as i2c:
+            self._buffer[0] = command
+            i2c.write(self._buffer, end=1)
+            time.sleep(Mode.delay[self._mode])
+            i2c.readinto(self._buffer)
+
+        # separate the read data
+        temp_data = self._buffer[0:2]
+        temp_crc = self._buffer[2]
+        humidity_data = self._buffer[3:5]
+        humidity_crc = self._buffer[5]
+
+        # check CRC of bytes
+        if temp_crc != self._crc8(temp_data) or humidity_crc != self._crc8(
+            humidity_data
+        ):
+            raise RuntimeError("Invalid CRC calculated")
+
+        # decode data into human values:
+        # convert bytes into 16-bit signed integer
+        # convert the LSB value to a human value according to the datasheet
+        temperature = struct.unpack_from(">H", temp_data)[0]
+        temperature = -45.0 + 175.0 * temperature / 65535.0
+
+        # repeat above steps for humidity data
+        humidity = struct.unpack_from(">H", humidity_data)[0]
+        humidity = -6.0 + 125.0 * humidity / 65535.0
+        humidity = max(min(humidity, 100), 0)
+
+        return (temperature, humidity)
+
+    ## CRC-8 formula from page 14 of SHTC3 datasheet
+    # https://media.digikey.com/pdf/Data%20Sheets/Sensirion%20PDFs/HT_DS_SHTC3_D1.pdf
+    # Test data [0xBE, 0xEF] should yield 0x92
+
+    @staticmethod
+    def _crc8(buffer):
+        crc = 0xFF
+        for byte in buffer:
+            crc ^= byte
+            for _ in range(8):
+                if crc & 0x80:
+                    crc = (crc << 1) ^ 0x31
+                else:
+                    crc = crc << 1
+        return crc & 0xFF  # return the bottom 8 bits

docs/conf.py

@@ -29,8 +29,11 @@
 
 
 intersphinx_mapping = {
-    "python": ("https://docs.python.org/3.4", None),"BusDevice": ("https://circuitpython.readthedocs.io/projects/busdevice/en/latest/", None),
-
+    "python": ("https://docs.python.org/3.4", None),
+    "BusDevice": (
+        "https://circuitpython.readthedocs.io/projects/busdevice/en/latest/",
+        None,
+    ),
     "CircuitPython": ("https://circuitpython.readthedocs.io/en/latest/", None),
 }
 

docs/index.rst

@@ -23,14 +23,10 @@ Table of Contents
 .. toctree::
     :caption: Tutorials
 
-.. todo:: Add any Learn guide links here. If there are none, then simply delete this todo and leave
-    the toctree above for use later.
-
 .. toctree::
     :caption: Related Products
 
-.. todo:: Add any product links here. If there are none, then simply delete this todo and leave
-    the toctree above for use later.
+    Purchase SHT40 breakout <https://www.adafruit.com/products/4885>
 
 .. toctree::
     :caption: Other Links

examples/sht4x_simpletest.py

@@ -1,3 +1,24 @@
-# SPDX-FileCopyrightText: 2017 Scott Shawcroft, written for Adafruit Industries
+# SPDX-FileCopyrightText: Copyright (c) 2020 ladyada for Adafruit Industries
 #
-# SPDX-License-Identifier: Unlicense
+# SPDX-License-Identifier: MIT
+
+import time
+import busio
+import board
+import adafruit_sht4x
+
+i2c = busio.I2C(board.SCL, board.SDA)
+sht = adafruit_sht4x.SHT4x(i2c)
+print("Found SHT4x with serial number", hex(sht.serial_number))
+
+sht.mode = adafruit_sht4x.Mode.NOHEAT_HIGHPRECISION
+# Can also set the mode to enable heater
+# sht.mode = adafruit_sht4x.Mode.LOWHEAT_100MS
+print("Current mode is: ", adafruit_sht4x.Mode.string[sht.mode])
+
+while True:
+    temperature, relative_humidity = sht.measurements
+    print("Temperature: %0.1f C" % temperature)
+    print("Humidity: %0.1f %%" % relative_humidity)
+    print("")
+    time.sleep(1)

setup.py

@@ -53,7 +53,7 @@
     ],
     # What does your project relate to?
     keywords="adafruit blinka circuitpython micropython sht4x temperature humidity sensor "
-             "sht40 sensirion",
+    "sht40 sensirion",
     # You can just specify the packages manually here if your project is
     # simple. Or you can use find_packages().
     # TODO: IF LIBRARY FILES ARE A PACKAGE FOLDER,