Difference between revisions of "ADXL345 Triple Axis Accelerometer Breakout"

Revision as of 02:38, 1 September 2012

Introduction

This is a breakout board for Analog Devices ADXL345 3-Axis Accelerometer.The ADXL345 is a small, thin, ultralow power, 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°.

Features

• Ultralow power: as low as 23 μA in measurement mode
• Fixed 10-bit resolution Full resolution, up to 13-bit resolution at ±16 g
• Single tap/double tap detection
• Activity/inactivity monitoring
• Free-fall detection
• Supply voltage range: 2.0 V to 3.6 V
• I/O voltage range: 1.7 V to VS
• SPI (3- and 4-wire) and I2C digital interfaces

Document

ADXL345 Datasheet

Usage

Here is the guide illustrates how to connect an Arduino to the ADXL335 breakout board. The following is a table describing which pins on the Arduino should be connected to the pins on the accelerometer:

File:ADX table.jpg

Example code

#include <Wire.h> // I2C library, gyroscope
// Accelerometer ADXL345
#define ACC (0xA7>>1)    //ADXL345 ACC address
#define A_TO_READ (6)        //num of bytes we are going to read each time (two bytes for each axis)
void initAcc() {
 //Turning on the ADXL345
 writeTo(ACC, 0x2D, 1<<3);      
 writeTo(ACC, 0x31, 0x0B);
 writeTo(ACC, 0x2C, 0x09);
 //by default the device is in +-2g range reading
}
void getAccelerometerData(int * result) {
 int regAddress = 0x32;    //first axis-acceleration-data register on the ADXL345
 byte buff[A_TO_READ];
 readFrom(ACC, regAddress, A_TO_READ, buff); //read the acceleration data from the ADXL345
 //each axis reading comes in 10 bit resolution, ie 2 bytes.  Least Significat Byte first!!
 //thus we are converting both bytes in to one int
 result[0] = (((int)buff[1]) << 8) | buff[0];   
 result[1] = (((int)buff[3])<< 8) | buff[2];
 result[2] = (((int)buff[5]) << 8) | buff[4];
}
void setup()
{
 Serial.begin(9600);
 Wire.begin();
 initAcc();
}
void loop()
{
int hx,hy,hz;
int acc[3];
getAccelerometerData(acc);
hx = acc[0];
hy = acc[1];
hz = acc[2];
Serial.print(" X=");
Serial.print(hx);
Serial.print(" Y=");
Serial.print(hy);
Serial.print(" Z=");
Serial.println(hz);
delay(50); 
}
//---------------- Functions
//Writes val to address register on ACC
void writeTo(int DEVICE, byte address, byte val) {
  Wire.beginTransmission(DEVICE); //start transmission to ACC 
  Wire.send(address);        // send register address
  Wire.send(val);        // send value to write
  Wire.endTransmission(); //end transmission
}
//reads num bytes starting from address register on ACC in to buff array
 void readFrom(int DEVICE, byte address, int num, byte buff[]) {
 Wire.beginTransmission(DEVICE); //start transmission to ACC 
 Wire.send(address);        //sends address to read from
 Wire.endTransmission(); //end transmission
 
 Wire.beginTransmission(DEVICE); //start transmission to ACC
 Wire.requestFrom(DEVICE, num);    // request 6 bytes from ACC
 int i = 0;
 while(Wire.available())    //ACC may send less than requested (abnormal)
 { 
   buff[i] = Wire.receive(); // receive a byte
   i++;
 }
 Wire.endTransmission(); //end transmission
}

How to buy

Click here to buy ADXL345 3-Axis Accelerometer Breakout