Python & CircuitPython

It's easy to use the FXOS8700 + FXAS21002C 9DoF sensor with Python and CircuitPython, and the Adafruit CircuitPython FXOS8700 and Adafruit CircuitPython FXAS21002C modules.  These module allows you to easily write Python code that reads the accelerometer, magnetometer, and gyroscope values from the sensors.  Note the advanced sensor fusion algorithm to compute absolute orientation is not currently supported--you can only read the raw sensor accelerometer, magnetometer, and gyroscope values!

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 9DoF to your board exactly as shown on the previous pages for Arduino.   Here's an example of wiring a Feather M0 to the sensor with an I2C connection:

  • Board 3V to sensor VIN
  • Board GND to sensor GND
  • Board SCL to sensor SCL
  • Board SDA to sensor SDA

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 with I2C:

  • Pi 3V3 to sensor VIN
  • Pi GND to sensor GND
  • Pi SCL to sensor SCL
  • Pi SDA to sensor SDA

CircuitPython Installation of FXOS8700 + FXAS21002C Library

Next you'll need to install both the Adafruit CircuitPython FXOS8700 and Adafruit CircuitPython FXAS21002C libraries 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.  For example the Circuit Playground Express guide has a great page on how to install the library bundle for both express and non-express boards.

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/Metro M0 basic you'll need to manually install the necessary libraries from the bundle:

  • adafruit_fxos8700.mpy
  • adafruit_fxas21002c.mpy
  • adafruit_bus_device

Before continuing make sure your board's lib folder or root filesystem has the adafruit_fxos8700.mpy, adafruit_fxas21002c.mpy and adafruit_bus_device files and folders copied over.

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

Python Installation of FXOS8700 + FXAS21002C 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-fxos8700
  • sudo pip3 install adafruit-circuitpython-fxas21002c

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 accelerometer, magnetometer, and gyroscope values 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 board
import busio
import adafruit_fxos8700
import adafruit_fxas21002c
i2c = busio.I2C(board.SCL, board.SDA)
fxos = adafruit_fxos8700.FXOS8700(i2c)
fxas = adafruit_fxas21002c.FXAS21002C(i2c)

Now you're ready to read values from the sensors using any of these properties.  For the FXOS8700:

  • accelerometer - A 3-tuple of X, Y, Z axis accelerometer values in meters per second squared.
  • magnetometer - A 3-tuple of X, Y, Z axis magnetometer values in gauss.

And for the FXAS21002C:

  • gyroscope - A 3-tuple of the X, Y, Z axis gyroscope values in radians per second.
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print('Acceleration (m/s^2): ({0:0.3f},{1:0.3f},{2:0.3f})'.format(*fxos.accelerometer))
print('Magnetometer (uTesla): ({0:0.3f},{1:0.3f},{2:0.3f})'.format(*fxos.magnetometer))
print('Gyroscope (radians/s): ({0:0.3f},{1:0.3f},{2:0.3f})'.format(*fxas.gyroscope))

See the FXOS8700 simpletest.py example for a complete demo of printing the accelerometer and magnetometer every second. Also see the FXAS21002C simpletest.py example for a complete demo of printing the accelerometer and magnetometer every second.  Save this as code.py on the board and examine the REPL output to see the range printed every second.

That's all there is to using the FXOS8700 and FXAS21002C sensors with CircuitPython!

Full Example Code

FXOS8700 test example:

# Simple demo of the FXOS8700 accelerometer and magnetometer.
# Will print the acceleration and magnetometer values every second.
import time

import board
import busio

import adafruit_fxos8700


# Initialize I2C bus and device.
i2c = busio.I2C(board.SCL, board.SDA)
sensor = adafruit_fxos8700.FXOS8700(i2c)
# Optionally create the sensor with a different accelerometer range (the
# default is 2G, but you can use 4G or 8G values):
#sensor = adafruit_fxos8700.FXOS8700(i2c, accel_range=adafruit_fxos8700.ACCEL_RANGE_4G)
#sensor = adafruit_fxos8700.FXOS8700(i2c, accel_range=adafruit_fxos8700.ACCEL_RANGE_8G)

# Main loop will read the acceleration and magnetometer values every second
# and print them out.
while True:
    # Read acceleration & magnetometer.
    accel_x, accel_y, accel_z = sensor.accelerometer
    mag_x, mag_y, mag_z = sensor.magnetometer
    # Print values.
    print('Acceleration (m/s^2): ({0:0.3f}, {1:0.3f}, {2:0.3f})'.format(accel_x, accel_y, accel_z))
    print('Magnetometer (uTesla): ({0:0.3f}, {1:0.3f}, {2:0.3f})'.format(mag_x, mag_y, mag_z))
    # Delay for a second.
    time.sleep(1.0)

FXAS21002C test example:

# Simple demo of the FXAS21002C gyroscope.
# Will print the gyroscope values every second.
import time

import board
import busio

import adafruit_fxas21002c


# Initialize I2C bus and device.
i2c = busio.I2C(board.SCL, board.SDA)
sensor = adafruit_fxas21002c.FXAS21002C(i2c)
# Optionally create the sensor with a different gyroscope range (the
# default is 250 DPS, but you can use 500, 1000, or 2000 DPS values):
#sensor = adafruit_fxas21002c.FXAS21002C(i2c, gyro_range=adafruit_fxas21002c.GYRO_RANGE_500DPS)
#sensor = adafruit_fxas21002c.FXAS21002C(i2c, gyro_range=adafruit_fxas21002c.GYRO_RANGE_1000DPS)
#sensor = adafruit_fxas21002c.FXAS21002C(i2c, gyro_range=adafruit_fxas21002c.GYRO_RANGE_2000DPS)

# Main loop will read the gyroscope values every second and print them out.
while True:
    # Read gyroscope.
    gyro_x, gyro_y, gyro_z = sensor.gyroscope
    # Print values.
    print('Gyroscope (radians/s): ({0:0.3f},  {1:0.3f},  {2:0.3f})'.format(gyro_x, gyro_y, gyro_z))
    # Delay for a second.
    time.sleep(1.0)
This guide was first published on Apr 14, 2017. It was last updated on Apr 14, 2017. This page (Python & CircuitPython) was last updated on Jul 21, 2019.