3-Axis Accelerometer & Acceleration Module GY-291 - Digital Output, SPI / I2C Interface - ADXL345

The ADXL345 is a 3-axis accelerometer with high resolution (13-bit) measurement at up to ±16 g. Digital output data is formatted as 16-bit twos complement and is accessible through either a SPI (3- or 4-wire) or I2C digital interface. The ADXL345 is well suited for mobile device applications. It measures the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion or shock. Its high resolution (3.9 mg/LSB) enables measurement of inclination changes less than 1.0°. Several special sensing functions are provided. Activity and inactivity sensing detect the presence or lack of motion by comparing the acceleration on any axis with user-set thresholds. Tap sensing detects single and double taps in any direction. Freefall sensing detects if the device is falling, can be mapped individually to either of two interrupt output pins. An integrated, patent pending memory management system with a 32-level first in, first out (FIFO) buffer can be used to store data to minimize host processor activity and lower overall system power consumption. Low power modes enable intelligent motion-based power management with threshold sensing and active acceleration measurement at extremely low power dissipation.

Features

• Power consumption scales automatically with bandwidth
• User-selectable resolution
• Single tap / Double tap detection
• Activity / Inactivity monitoring
• Free-Fall detection
• Full resolution, where resolution increases with g range, up to 13-bit resolution at ±16 g (maintaining 4 mg/LSB  scale factor in all g ranges)
• SPI (3- and 4-wire) and I2C digital interfaces
• Flexible interrupt modes mappable to either interrupt pin
• Measurement ranges selectable via serial command
• Bandwidth selectable via serial command
• 10,000 g shock survival

Specifications

Connect ADSL345 to Arduino

#include <Wire.h>
#include <ADXL345.h>


ADXL345 adxl; //variable adxl is an instance of the ADXL345 library

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

  //set activity/ inactivity thresholds (0-255)
  adxl.setActivityThreshold(75); //62.5mg per increment
  adxl.setInactivityThreshold(75); //62.5mg per increment
  adxl.setTimeInactivity(10); // how many seconds of no activity is inactive?
 
  //look of activity movement on this axes - 1 == on; 0 == off 
  adxl.setActivityX(1);
  adxl.setActivityY(1);
  adxl.setActivityZ(1);
 
  //look of inactivity movement on this axes - 1 == on; 0 == off
  adxl.setInactivityX(1);
  adxl.setInactivityY(1);
  adxl.setInactivityZ(1);
 
  //look of tap movement on this axes - 1 == on; 0 == off
  adxl.setTapDetectionOnX(0);
  adxl.setTapDetectionOnY(0);
  adxl.setTapDetectionOnZ(1);
 
  //set values for what is a tap, and what is a double tap (0-255)
  adxl.setTapThreshold(50); //62.5mg per increment
  adxl.setTapDuration(15); //625μs per increment
  adxl.setDoubleTapLatency(80); //1.25ms per increment
  adxl.setDoubleTapWindow(200); //1.25ms per increment
 
  //set values for what is considered freefall (0-255)
  adxl.setFreeFallThreshold(7); //(5 - 9) recommended - 62.5mg per increment
  adxl.setFreeFallDuration(45); //(20 - 70) recommended - 5ms per increment
 
  //setting all interupts to take place on int pin 1
  //I had issues with int pin 2, was unable to reset it
  adxl.setInterruptMapping( ADXL345_INT_SINGLE_TAP_BIT,   ADXL345_INT1_PIN );
  adxl.setInterruptMapping( ADXL345_INT_DOUBLE_TAP_BIT,   ADXL345_INT1_PIN );
  adxl.setInterruptMapping( ADXL345_INT_FREE_FALL_BIT,    ADXL345_INT1_PIN );
  adxl.setInterruptMapping( ADXL345_INT_ACTIVITY_BIT,     ADXL345_INT1_PIN );
  adxl.setInterruptMapping( ADXL345_INT_INACTIVITY_BIT,   ADXL345_INT1_PIN );
 
  //register interupt actions - 1 == on; 0 == off  
  adxl.setInterrupt( ADXL345_INT_SINGLE_TAP_BIT, 1);
  adxl.setInterrupt( ADXL345_INT_DOUBLE_TAP_BIT, 1);
  adxl.setInterrupt( ADXL345_INT_FREE_FALL_BIT,  1);
  adxl.setInterrupt( ADXL345_INT_ACTIVITY_BIT,   1);
  adxl.setInterrupt( ADXL345_INT_INACTIVITY_BIT, 1);
}

void loop(){
  
  //Boring accelerometer stuff   
  int x,y,z;  
  adxl.readAccel(&x, &y, &z); //read the accelerometer values and store them in variables  x,y,z

  // Output x,y,z values - Commented out
  //Serial.print(x);
  //Serial.print(y);
  //Serial.println(z);


  //Fun Stuff!    
  //read interrupts source and look for triggerd actions
  
  //getInterruptSource clears all triggered actions after returning value
  //so do not call again until you need to recheck for triggered actions
   byte interrupts = adxl.getInterruptSource();
  
  // freefall
  if(adxl.triggered(interrupts, ADXL345_FREE_FALL)){
    Serial.println("freefall");
    //add code here to do when freefall is sensed
  } 
  
  //inactivity
  if(adxl.triggered(interrupts, ADXL345_INACTIVITY)){
    Serial.println("inactivity");
     //add code here to do when inactivity is sensed
  }
  
  //activity
  if(adxl.triggered(interrupts, ADXL345_ACTIVITY)){
    Serial.println("activity"); 
     //add code here to do when activity is sensed
  }
  
  //double tap
  if(adxl.triggered(interrupts, ADXL345_DOUBLE_TAP)){
    Serial.println("double tap");
     //add code here to do when a 2X tap is sensed
  }
  
  //tap
  if(adxl.triggered(interrupts, ADXL345_SINGLE_TAP)){
    Serial.println("tap");
     //add code here to do when a tap is sensed
  } 

 
}