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:
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:
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-msa3xx
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:
import time import board import adafruit_msa3xx i2c = board.I2C() msa = adafruit_msa3xx.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:
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT
import time
import board
from adafruit_msa3xx import MSA301
i2c = board.I2C() # uses board.SCL and board.SDA
# i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller
msa = MSA301(i2c)
while True:
print("%f %f %f" % msa.acceleration)
time.sleep(0.5)
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT
import time
import board
from adafruit_msa3xx import MSA301
i2c = board.I2C() # uses board.SCL and board.SDA
# i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller
msa = MSA301(i2c)
msa.enable_tap_detection()
while True:
if msa.tapped:
print("Single Tap!")
time.sleep(0.01)
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