htu21d

Python 2.7 library for the Adafruit HTU21D-F Humidity and Temperature sensor breakout board. https://www.adafruit.com/product/1899

Based on the code of the Adafruit_Python_HTU21D library written by Massimo Gaggero for Adafruit Industries.

The original Adafruit library only partially supports Python 2.7, which I am using for my Raspberry Pi-Weatherstation-Project.Therefore, I had to modify the library for full support of Python 2.7.

Additionally, I replaced the original function 'read_dewpoint()' by the function 'dewpoint()', which now can be called with temperature and humidity as parameters. If the function is called without passing the temperature and/or the relative humidity, the function reads the sensors current value(s).

For higher accuracy, the dew point is now calculated based on an algorithm published by Stefan Ochs. This algorithm distinguishes temperatures above or equal to 0 deg. Celsius from temperatures below 0 deg. Celsius. For further information see: https://www.wetterochs.de/wetter/feuchte.html

Warning:

• tested only on RPi-3 running Raspbian Stretch and Python 2.7.
• for additional warnings, see https://github.com/mgaggero/Adafruit_Python_HTU21D

Installation

Setuptools

The following commands install the library system wide:

git clone https://github.com/HoK-matic/htu21d.git
cd htu21d
sudo python setup.py install

Permissions and privilieges

Accessing I2C devices usually requires root privileges or privileged group membership. These can be obtained with:

• the use of sudo to run the program;
• adding the user that runs the program to the I2C's device owning group, if exists.

Usage

>>> import htu21d.htu21d as htu

>>> sensor = htu.HTU21D()

>>> sensor.read_temperature()
22.2919711914062

>>> sensor.read_humidity()
53.1524365234375

>>> sensor.dewpoint()
12.3014062484367

>>> sensor.reset()