Python & CircuitPython

It's easy to use the MSA301 sensor with CircuitPython and the Adafruit CircuitPython MSA301 module.  This module allows you to easily write Python code that reads the acceleration and adjust the measurement settings.

You can use this sensor with any CircuitPython microcontroller board or with a Linux single board computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.

CircuitPython Microcontroller Wiring

First wire up a MSA301 to your board exactly as follows. Here is an example of the MSA301 wired to a Feather using I2C:

  • Board 3V to sensor VIN
  • Board GND to sensor GND
  • Board SCL to sensor SCL
  • Board SDA to sensor SDA
Note: This breakout includes pullup resistors on the I2C lines, no external pullups are required.

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 MSA301 Library

You'll need to install the Adafruit CircuitPython MSA301 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_msa301.mpy
  • adafruit_bus_device
  • adafruit_register

Before continuing make sure your board's lib folder or root filesystem has the adafruit_msa301.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 MSA301 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-msa301

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 acceleration 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_msa301

i2c = busio.I2C(board.SCL, board.SDA)

msa = adafruit_msa301.MSA301(i2c)

Now you're ready to read the acceleration values from the sensor using the property provided by the library. 

Here is an example showing how to print the acceleration values:

You can find more details about what the library allows by reading the library documentation.

That's it! Using the MSA301 accelerometer with CircuitPython makes it easy to get started.

Tap Detection

Next, let's take a look at another neat feature of the MSA301: Tap detection!

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

Next we'll configure tap detection by calling enable_tap_detection. Here we're giving an example of the different parameters you can tune, but calling it without any arguments will set it to detect single taps with reasonable settings defaults:

Finally we set up a loop, calling the tapped property to check and print if a double tap has been detected, since we passed 2 to the enable_tap_detection which specifies double tap detection:

Acceleration Example Code

import time
import board
import busio
import adafruit_msa301

i2c = busio.I2C(board.SCL, board.SDA)

msa = adafruit_msa301.MSA301(i2c)
while True:
    print("%f %f %f"%msa.acceleration)
    time.sleep(0.5)

Tap Detection Example Code

import time
import board
import busio
import adafruit_msa301

i2c = busio.I2C(board.SCL, board.SDA)

msa = adafruit_msa301.MSA301(i2c)

msa.enable_tap_detection()

while True:
    if msa.tapped:
        print("Single Tap!")
    time.sleep(0.01)
This guide was first published on Aug 23, 2019. It was last updated on Aug 23, 2019. This page (Python & CircuitPython) was last updated on Feb 17, 2020.