ADXL 345 Breakout Board

Der ADXL345 ist ein stromsparender (40µA beim Messen, 0,1µA im StandBy) 3-Achsen Beschleunigungssensor, mit einer Auflösung von 13-Bit ist er sehr genau (4mg/LSB).
Die Messadten lassen sich über SPI (3 oder 4 Wire Betrieb) oder I2C auslesen.

Der Sensor enthält zahlreiche eingebaute Funktionen, wie z.B. Freie Fall Erkennung, Überschreitung eines Voreingestellten Messwertes.

Technische Daten:

• 2.0-3.6VDC Supply Voltage
• Ultra Low Power: 40uA in measurement mode, 0.1uA in standby@ 2.5V
• Tap/Double Tap Detection
• Free-Fall Detection
• SPI and I2C interfaces

 

 

#include <Wire.h>

#define DEVICE (0x53)    //ADXL345 device address
#define TO_READ (6)        //num of bytes we are going to read each time (two bytes for each axis)

byte buff[TO_READ] ;    //6 bytes buffer for saving data read from the device
char str[512];                      //string buffer to transform data before sending it to the serial port
double g = 9.806;
int time;

void setup()
{
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start serial for output

  //Turning on the ADXL345
  writeTo(DEVICE, 0x2D, 0);     
  writeTo(DEVICE, 0x2D, 16);
  writeTo(DEVICE, 0x2D, 8);
}

void loop()
{
//  Serial.println('Neue Messung');
//  while(true){
  int regAddress = 0x32;    //first axis-acceleration-data register on the ADXL345
  int x, y, z;
  double ax, ay , az;
  readFrom(DEVICE, regAddress, 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
  x = (((int)buff[1]) << 8) | buff[0];  
  y = (((int)buff[3])<< 8) | buff[2];
  z = (((int)buff[5]) << 8) | buff[4];

  time = millis();

  time = time * 0.001;

  //we send the x y z values as a string to the serial port
  sprintf(str, "%d %d %d", x, y, z); 
  Serial.print(str);
  Serial.print(" ");
  Serial.println(time);

  //It appears that delay is needed in order not to clog the port
  delay(50);

}

//---------------- Functions
//Writes val to address register on device
void writeTo(int device, byte address, byte val) {
  Wire.beginTransmission(device); //start transmission to device
  Wire.write(address);        // send register address
  Wire.write(val);        // send value to write
  Wire.endTransmission(); //end transmission
}

//reads num bytes starting from address register on device in to buff array
void readFrom(int device, byte address, int num, byte buff[]) {
  Wire.beginTransmission(device); //start transmission to device
  Wire.write(address);        //sends address to read from
  Wire.endTransmission(); //end transmission

    Wire.beginTransmission(device); //start transmission to device
  Wire.requestFrom(device, num);    // request 6 bytes from device

  int i = 0;
  while(Wire.available())    //device may send less than requested (abnormal)
  {
    buff[i] = Wire.read(); // receive a byte
    i++;
  }
  Wire.endTransmission(); //end transmission

}