MMA8452Q Triple Axis Accelerometer

The MMA8452Q is a low-power, three-axis, capacitive MEMS accelerometer with 8 or 12 bits of resolution. The surface mount chip is located on a break out board with inputs to ground, power, I2C, and two external interrupts pins.

Hello World

Import programMMA8452_Demo

The main.cpp program below demonstrates a simple way to interface with the MMA8452 accelerometer. The function reads in the acceleration data in the X, Y, and Z directions and displays them through a serial com port on a PC. The Putty Output figure below shows the output of the accelerometer using Putty. The program also dims or brightens the mbed LEDs 1-3 based on whether or not they are at 'level'( 0 Gs) or above respectively. The video below previews the code in action.

Last commit 17 Oct 2014 by Ivan Rush

Library

Import libraryMMA8452

Library for driving the MMA8452 accelerometer over I2C

Last commit 07 Mar 2014 by Ashley Mills

Datasheet

http://www.freescale.com/files/sensors/doc/data_sheet/MMA8452Q.pdf

Notes

Wiring

MMA8452Q attached to mbed on a breadboard.
mbed-triple

MMA8452Q schematic.
Schematic

Pinout Table

MMA8452Q pinsMbed pins
1 VccVout (3.3V)
2 SDAP28 (SDA)
3 SCLP27 (SCL)
4 I1Any DigitalOut Pins
5 I2Any DigitalOut Pins
6 GNDGND

API Documentation

Import library
MMA8452 - MMA8452 Class Reference

Public Member Functions

MMA8452 (PinName sda, PinName scl, int frequency)
Create an accelerometer object connected to the specified I2C pins.
~MMA8452 ()
Destructor.
int activate ()
Puts the MMA8452 in active mode.
int standby ()
Puts the MMA8452 in standby.
int getDeviceID (char *dst)
Read the device ID from the accelerometer (should be 0x2a)
int getStatus (char *dst)
Read the MMA8452 status register.
int readXYZRaw (char *dst)
Read the raw x, y, an z registers of the MMA8452 in one operation.
int readXRaw (char *dst)
Read the raw x register into the provided buffer.
int readYRaw (char *dst)
Read the raw y register into the provided buffer.
int readZRaw (char *dst)
Read the raw z register into the provided buffer.
int readXYZCounts (int *x, int *y, int *z)
Read the x, y, and z signed counts of the MMA8452 axes.
int readXCount (int *x)
Read the x axes signed count.
int readYCount (int *y)
Read the y axes signed count.
int readZCount (int *z)
Read the z axes signed count.
int readXYZGravity (double *x, double *y, double *z)
Read the x, y, and z accelerations measured in G.
int readXGravity (double *x)
Read the x gravity in G into the provided double pointer.
int readYGravity (double *y)
Read the y gravity in G into the provided double pointer.
int readZGravity (double *z)
Read the z gravity in G into the provided double pointer.
int isXYZReady ()
Returns 1 if data has been internally sampled (is available) for all axes since last read, 0 otherwise.
int isXReady ()
Returns 1 if data has been internally sampled (is available) for the x-axis since last read, 0 otherwise.
int isYReady ()
Returns 1 if data has been internally sampled (is available) for the y-axis since last read, 0 otherwise.
int isZReady ()
Returns 1 if data has been internally sampled (is available) for the z-axis since last read, 0 otherwise.
int readRegister (char addr, char *dst)
Reads a single byte from the specified MMA8452 register.
int readRegister (char addr, char *dst, int nbytes)
Reads n bytes from the specified MMA8452 register.
int writeRegister (char addr, char data)
Write to the specified MMA8452 register.
int writeRegister (char addr, char *data, int nbytes)
Write a data buffer to the specified MMA8452 register.

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