It's easy to use the HTS221 sensor with Python and CircuitPython, and the Adafruit CircuitPython HTS221 module.  This module allows you to easily write Python code that reads humidity and temperature measurements. 

You can use this sensor 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 a HTS221 to your board for an I2C connection, exactly  as shown below.  Here's an example of wiring a Feather M4 to the sensor with I2C:

  • 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:

  • Pi 3V to sensor VCC (red wire)
  • Pi GND to sensor GND (black wire)
  • Pi SCL to sensor SCL (yellow wire)
  • Pi SDA to sensor SDA (blue wire)

CircuitPython Installation of HTS221 Library

You'll need to install the Adafruit CircuitPython HTS221 library on your CircuitPython board.

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  Our CircuitPython starter guide has a great page on how to install the library bundle.

For non-express boards like the Trinket M0 or Gemma M0, you'll need to manually install the necessary libraries from the bundle:

  • adafruit_hts221.mpy
  • adafruit_bus_device
  • adafruit_register

Before continuing make sure your board's lib folder or root filesystem has the adafruit_hts221.mpy, adafruit_bus_device, and adafruit_register files and folders copied over.

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

Python Installation of HTS221 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:

  • sudo pip3 install adafruit-circuitpython-hts221

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 & Python Usage

To demonstrate the usage of the sensor we'll initialize it and read the humidity and temperature measurements from the board's Python REPL.

Run the following code to import the necessary modules and initialize the I2C connection with the sensor:

Download: file
import time
import board
import busio
import adafruit_hts221

i2c = busio.I2C(board.SCL, board.SDA)
hts = adafruit_hts221.HTS221(i2c)

Now you're ready to read values from the sensor using these properties:

  • relative_humidity - The relative humidity measured by the sensor, this is a value from 0-100%.
  • temperature - The temperature measured by the sensor, a value in degrees Celsius.
Download: file
print("Relative Humidity: %.2f %% rH" % hts.relative_humidity)
print("Temperature: %.2f C" % hts.temperature)
import time
import board
import busio
import adafruit_hts221

i2c = busio.I2C(board.SCL, board.SDA)
hts = adafruit_hts221.HTS221(i2c)
while True:
    print("Relative Humidity: %.2f %% rH" % hts.relative_humidity)
    print("Temperature: %.2f C" % hts.temperature)
    print("")
    time.sleep(1)
This guide was first published on Mar 17, 2020. It was last updated on Mar 17, 2020.
This page (Python & CircuitPython) was last updated on Oct 24, 2020.