It's easy to use the LIS3MDL sensor with CircuitPython and the Adafruit CircuitPython LIS3MDL library. This library will allow you to easily write Python code that reads the magnetometer values from the sensor.
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 LIS3MDL breakout to your board 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's 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 to the sensor using 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 LIS3MDL Library
You'll need to install the Adafruit CircuitPython LIS3MDL 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_lis3mdl.mpy
- adafruit_bus_device
- adafruit_register
Before continuing make sure your board's lib folder or root filesystem has the adafruit_lis3mdl.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 LIS3MDL 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-lis3mdl
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 magnetometer measurements from the board's Python REPL.
Run the following code to import the necessary modules and initialize the I2C connection with the sensor:
import time import board import busio import adafruit_lis3mdl i2c = busio.I2C(board.SCL, board.SDA) sensor = adafruit_lis3mdl.LIS3MDL(i2c)
Now you're ready to read values from the magnetometer using the magnetic property which returns a 3-tuple of the X, Y, and Z magnetometer readings in micro-Teslas (uT)
mag_x, mag_y, mag_z = sensor.magnetic
print('X:{0:10.2f}, Y:{1:10.2f}, Z:{2:10.2f} uT'.format(mag_x, mag_y, mag_z))
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT
""" Display magnetometer data once per second """
import time
import board
import adafruit_lis3mdl
i2c = board.I2C() # uses board.SCL and board.SDA
# i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller
sensor = adafruit_lis3mdl.LIS3MDL(i2c)
while True:
mag_x, mag_y, mag_z = sensor.magnetic
print("X:{0:10.2f}, Y:{1:10.2f}, Z:{2:10.2f} uT".format(mag_x, mag_y, mag_z))
print("")
time.sleep(1.0)
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