ESP32 and MMA8451 accelerometer example

The MMA8451 is a low-power accelerometer with 14 bits of resolution, with the following features:

  • Embedded functions with flexible user-programmable options, configurable to two interrupt pins
  • Embedded interrupt functions for overall power savings relieving the host processor from continuously polling data
  • 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
  • Inertial wake-up 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 to 3.6-volt supply voltage
  • 1.6 to 3.6-volt interface voltage
  • ±2g/±4g/±8g 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 (operates to 2.25 MHz with 4.7 kΩ pull-up)
  • 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

Again due to the size and package of the module its easier to buy a module, here is one that I purchased.

MMA8451
MMA8451

 

Connection

I used the following connection from the module above to my Lolin 32 module

Lolin32 Connection Module Connection
3v3 VCC_IN
Gnd Gnd
SDA 21 SDA
SCL 22 SCL

 

Here is a layout showing this

lolin32 and mma8451
lolin32 and mma8451

Code

This requires the Adafruit library from https://github.com/adafruit/Adafruit_MMA8451_Library/archive/master.zip

I had to edit the Adafruit header file called Adafruit_MMA8451.h as my device was address 0x1c (28), I discovered this using an I2C scanner

#define MMA8451_DEFAULT_ADDRESS                 (0x1C)

#include <Wire.h>
#include "Adafruit_MMA8451.h"
#include <Adafruit_Sensor.h>

Adafruit_MMA8451 mma = Adafruit_MMA8451();

void setup(void) {
Serial.begin(9600);

Serial.println("Adafruit MMA8451 test!");

if (! mma.begin()) {
Serial.println("Couldnt start");
while (1);
}
Serial.println("MMA8451 found!");

mma.setRange(MMA8451_RANGE_2_G);

Serial.print("Range = "); Serial.print(2 << mma.getRange());
Serial.println("G");

}

void loop() {
// Read the 'raw' data in 14-bit counts
mma.read();
Serial.print("X:\t"); Serial.print(mma.x);
Serial.print("\tY:\t"); Serial.print(mma.y);
Serial.print("\tZ:\t"); Serial.print(mma.z);
Serial.println();

/* Get a new sensor event */
sensors_event_t event;
mma.getEvent(&event);

/* Display the results (acceleration is measured in m/s^2) */
Serial.print("X: \t"); Serial.print(event.acceleration.x); Serial.print("\t");
Serial.print("Y: \t"); Serial.print(event.acceleration.y); Serial.print("\t");
Serial.print("Z: \t"); Serial.print(event.acceleration.z); Serial.print("\t");
Serial.println("m/s^2 ");

/* Get the orientation of the sensor */
uint8_t o = mma.getOrientation();

switch (o) {
case MMA8451_PL_PUF:
Serial.println("Portrait Up Front");
break;
case MMA8451_PL_PUB:
Serial.println("Portrait Up Back");
break;
case MMA8451_PL_PDF:
Serial.println("Portrait Down Front");
break;
case MMA8451_PL_PDB:
Serial.println("Portrait Down Back");
break;
case MMA8451_PL_LRF:
Serial.println("Landscape Right Front");
break;
case MMA8451_PL_LRB:
Serial.println("Landscape Right Back");
break;
case MMA8451_PL_LLF:
Serial.println("Landscape Left Front");
break;
case MMA8451_PL_LLB:
Serial.println("Landscape Left Back");
break;
}
Serial.println();
delay(500);

}

Output

Open the serial monitor and you will see something like this, I was moving the sensor about hence the various readings

X: -2166 Y: 1872 Z: 2186X: -2166 Y: 1872 Z: 2186
X: -4.92 Y: 5.99 Z: 4.87 m/s^2
Landscape Left Front

X: -224 Y: -2020 Z: 3188
X: -5.10 Y: -3.19 Z: 7.00 m/s^2
Portrait Up Front

X: -1244 Y: -2208 Z: 788
X: -5.88 Y: -3.77 Z: 2.74 m/s^2
Landscape Left Front

X: 514 Y: -1170 Z: -3436
X: 1.34 Y: -2.83 Z: -8.53 m/s^2
Portrait Up Back

X: 1858 Y: 1258 Z: -2694
X: 3.91 Y: 3.21 Z: -1.56 m/s^2
Landscape Right Back

Links

Here is a link to the module

AliExpress.com Product – GY-45 MMA8451 Modules Digital Triaxial Accelerometer High-precision Inclination Module