Raspberry Pi Pico and MMA8451Q accelerometer circuitpython example

In this article we connect a MMA8451Q accelerometer to a Raspberry Pi Pico running Circuitpython

Sensor Information

The MMA8451Q is a smart, low-power, three-axis, capacitive, micromachined accelerometer with 14 bits of resolution. This accelerometer is packed with embedded functions with flexible user programmable options, configurable to two interrupt pins.

Embedded interrupt functions allow for overall power savings relieving the host processor from continuously polling data.

There is access to both low-pass filtered data as well as high-pass filtered data, which minimizes the data analysis required for jolt detection and faster transitions.

The device can be configured to generate inertial wakeup interrupt signals from any combination of the configurable embedded functions allowing the MMA8451Q to monitor events and remain in a low-power mode during periods of inactivity.

Features

• 1.95 V to 3.6 V supply voltage
• 1.6 V to 3.6 V interface voltage
• ±2 g/±4 g/±8 g dynamically selectable full scale
• Output data rates (ODR) from 1.56 Hz to 800 Hz
• 99 μg/√Hz noise
• 14-bit and 8-bit digital output
• I2C digital output interface
• Two programmable interrupt pins for seven interrupt sources
• Three embedded channels of motion detection
— Freefall or motion detection: one channel
— Pulse detection: one channel
— Jolt detection: one channel
• Orientation (portrait/landscape) detection with programmable hysteresis
• Automatic ODR change for auto-wake and return to sleep
• 32-sample FIFO
• High-pass filter data available per sample and through the FIFO
• Self-test
• Current consumption: 6 μA to 165 μA

Parts Required

 

Name	Link
Pico	Raspberry Pi Pico Development Board
MMA8451	MMA8451 Digital Triaxial Accelerometer High-precision Inclination Module
Connecting cables	Aliexpress link Amazon.com link Ebay link

 

Schematic/Connection

Black for GND
Red for V+
Blue for SDA
Yellow for SCL

So color coded for ease of use, this layout shows a connection to the module

Code Example

I used Thonny for development

The following is based on a library , I copied the adafruit_mma8451.mpy library for this device to the lib folder on my Raspberry Pi Pico – https://circuitpython.org/libraries

This is the basic example which comes with the library

[codesyntax lang=”python”]

import time
import board
import adafruit_mma8451
import busio

i2c = busio.I2C(scl=board.GP1, sda=board.GP0) # uses board.SCL and board.SDA

sensor = adafruit_mma8451.MMA8451(i2c, address=0x1C)

# Main loop to print the acceleration and orientation every second.
while True:
    x, y, z = sensor.acceleration
    print(
        "Acceleration: x={0:0.3f}m/s^2 y={1:0.3f}m/s^2 z={2:0.3f}m/s^2".format(x, y, z)
    )
    orientation = sensor.orientation
    # Orientation is one of these values:
    #  - PL_PUF: Portrait, up, front
    #  - PL_PUB: Portrait, up, back
    #  - PL_PDF: Portrait, down, front
    #  - PL_PDB: Portrait, down, back
    #  - PL_LRF: Landscape, right, front
    #  - PL_LRB: Landscape, right, back
    #  - PL_LLF: Landscape, left, front
    #  - PL_LLB: Landscape, left, back
    print("Orientation: ", end="")
    if orientation == adafruit_mma8451.PL_PUF:
        print("Portrait, up, front")
    elif orientation == adafruit_mma8451.PL_PUB:
        print("Portrait, up, back")
    elif orientation == adafruit_mma8451.PL_PDF:
        print("Portrait, down, front")
    elif orientation == adafruit_mma8451.PL_PDB:
        print("Portrait, down, back")
    elif orientation == adafruit_mma8451.PL_LRF:
        print("Landscape, right, front")
    elif orientation == adafruit_mma8451.PL_LRB:
        print("Landscape, right, back")
    elif orientation == adafruit_mma8451.PL_LLF:
        print("Landscape, left, front")
    elif orientation == adafruit_mma8451.PL_LLB:
        print("Landscape, left, back")
    time.sleep(1.0)

[/codesyntax]

Output

Here is what I saw in Thonny REPL window

Acceleration: x=-1.470m/s^2 y=6.742m/s^2 z=6.311m/s^2
Orientation: Portrait, down, front
Acceleration: x=1.839m/s^2 y=7.034m/s^2 z=-6.416m/s^2
Orientation: Portrait, down, back
Acceleration: x=9.840m/s^2 y=1.140m/s^2 z=2.442m/s^2
Orientation: Landscape, right, front
Acceleration: x=3.170m/s^2 y=4.707m/s^2 z=-7.853m/s^2
Orientation: Portrait, down, back
Acceleration: x=1.523m/s^2 y=6.713m/s^2 z=-7.072m/s^2
Orientation: Portrait, down, back

Links