It's easy to use the HDC3021 with Python or CircuitPython, and the Adafruit_CircuitPython_HDC302x module. This module allows you to easily write Python code to read temperature and humidity data from the sensor.
You can use this driver with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.
CircuitPython Microcontroller Wiring
First wire up the sensor to your board exactly as follows. The following is the sensor wired to a Feather RP2040 using the STEMMA connector:
-
Board STEMMA 3V to sensor VIN (red wire)
-
Board STEMMA GND to sensor GND (black wire)
-
Board STEMMA SCL to sensor SCL (yellow wire)
- Board STEMMA SDA to sensor SDA (blue wire)
The following is the sensor wired to a Feather RP2040 using a solderless breadboard:
-
Board 3V to sensor VIN (red wire)
-
Board GND to sensor GND (black wire)
-
Board SCL to sensor SCL (yellow wire)
- Board SDA to sensor SDA (blue wire)
Python Computer Wiring
Since there are dozens of Linux computers/boards you can use, we will show wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to see whether your platform is supported.
Here's the Raspberry Pi wired with I2C using the STEMMA connector:
-
Pi 3V to sensor VIN (red wire)
-
Pi GND to sensor GND (black wire)
-
Pi SCL to sensor SCL (yellow wire)
- Pi SDA to sensor SDA (blue wire)
Here's the Raspberry Pi wired with I2C using a solderless breadboard:
-
Pi 3V to sensor VIN (red wire)
-
Pi GND to sensor GND (black wire)
-
Pi SCL to sensor SCL (yellow wire)
- Pi SDA to sensor SDA (blue wire)
Python Installation of HDC302x Library
You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!
Once that's done, from your command line run the following command:
pip3 install adafruit-circuitpython-hdc302x
If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!
CircuitPython Usage
To use with CircuitPython, you need to first install the Adafruit_CircuitPython_HDC302x library, and its dependencies, into the lib folder on your CIRCUITPY drive. Then you need to update code.py with the example script.
Thankfully, we can do this in one go. In the example below, click the Download Project Bundle button below to download the necessary libraries and the code.py file in a zip file. Extract the contents of the zip file, and copy the entire lib folder and the code.py file to your CIRCUITPY drive.
Your CIRCUITPY/lib folder should contain the following folder and file:
- adafruit_bus_device/
- adafruit_hdc302x.mpy
Python Usage
Once you have the library pip3 installed on your computer, copy or download the following example to your computer, and run the following, replacing code.py with whatever you named the file:
python3 code.py
Example Code
If running CircuitPython: Once everything is saved to the CIRCUITPY drive, connect to the serial console to see the data printed out!
If running Python: The console output will appear wherever you are running Python.
# SPDX-FileCopyrightText: 2024 Liz Clark for Adafruit Industries
#
# SPDX-License-Identifier: MIT
"""HDC302x simple test"""
import time
import board
import adafruit_hdc302x
i2c = board.I2C()
sensor = adafruit_hdc302x.HDC302x(i2c)
while True:
print(f"Temperature: {sensor.temperature:0.1f}°C")
print(f"Relative Humidity: {sensor.relative_humidity:0.1f}%")
print()
time.sleep(2)
The HDC3021 is instantiated over I2C. Then in the loop, the temperature and humidity readings are printed to the serial monitor every two seconds.
Page last edited January 22, 2025
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