KS0128 keyestudio EASY plug ADXL345 Three Axis Acceleration Module

1. Introduction

The ADXL345 module is a low power, 3-axis MEMS accelerometer with high resolution (13-bit) and measurement at up to ±16g (gravitational force).

Digital output data is formatted as 16-bit twos complement, and is accessible through either a SPI or I2C digital interface.

The ADXL345 is well suited to measures the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion or shock.

This module needs to be used together with EASY plug control board.

Special Note:

The sensor/module is equipped with the RJ11 6P6C interface, compatible with our keyestudio EASY plug Control Board with RJ11 6P6C interface.

If you have the control board of other brands, it is also equipped with the RJ11 6P6C interface but has different internal line sequence, can’t be used compatibly with our sensor/module.

2. Features

• Connector: Easy plug

• Working Voltage: 2.0-3.6V

• Ultra Low Power @2.5v: 40uA /working mode; 0.1uA / standby mode

• Communication interface: I2C / SPI

• Tap/Double Tap Detection

• Free-Fall Detection

3. Technical Details

• Dimensions: 41mm * 20mm * 18mm

• Weight: 4.6g

4. Connect It Up

Connect the EASY Plug ADXL345 Acceleration module to control board using an RJ11 cable. Then connect the control board to your PC with a USB cable.

5. Upload the Code

Download code: Code

 #include <Wire.h>    // place file “Wire.h” under the directory “libraries” of Arduino
// Registers for ADXL345
#define ADXL345_ADDRESS (0xA6 >> 1)  // address for device is 8 bit but shift to the
                                     // right by 1 bit to make it 7 bit because the
                                     // wire library only takes in 7 bit addresses
#define ADXL345_REGISTER_XLSB (0x32)

int accelerometer_data[3];
// void because this only tells the cip to send data to its output register
// writes data to the slave's buffer
void i2c_write(int address, byte reg, byte data) 
{
  // Send output register address
  Wire.beginTransmission(address);
  // Connect to device
  Wire.write(reg);
  // Send data
  Wire.write(data); //low byte
  Wire.endTransmission();
}

// void because using pointers
// microcontroller reads data from the sensor's input register
void i2c_read(int address, byte reg, int count, byte* data) 
{
  // Used to read the number of data received
  int i = 0;
  // Send input register address
  Wire.beginTransmission(address);
  // Connect to device
  Wire.write(reg);
  Wire.endTransmission();

  // Connect to device
  Wire.beginTransmission(address);
  // Request data from slave
  // Count stands for number of bytes to request
  Wire.requestFrom(address, count);
  while(Wire.available()) // slave may send less than requested
  {
    char c = Wire.read(); // receive a byte as character
    data[i] = c;
    i++;
  }
  Wire.endTransmission();
}

void init_adxl345() 
{
  byte data = 0;
  i2c_write(ADXL345_ADDRESS, 0x31, 0x0B);   // 13-bit mode  +_ 16g
  i2c_write(ADXL345_ADDRESS, 0x2D, 0x08);   // Power register

  i2c_write(ADXL345_ADDRESS, 0x1E, 0x00);   // x
  i2c_write(ADXL345_ADDRESS, 0x1F, 0x00);   // Y
  i2c_write(ADXL345_ADDRESS, 0x20, 0x05);   // Z
 
  // Check to see if it worked!
  i2c_read(ADXL345_ADDRESS, 0X00, 1, &data);
  if(data==0xE5)
    Serial.println("it work Success");
  else
    Serial.println("it work Fail");
}

void read_adxl345() 
{
  byte bytes[6];
  memset(bytes,0,6);

  // Read 6 bytes from the ADXL345
  i2c_read(ADXL345_ADDRESS, ADXL345_REGISTER_XLSB, 6, bytes);
  // Unpack data
  for (int i=0;i<3;++i) 
  {
    accelerometer_data[i] = (int)bytes[2*i] + (((int)bytes[2*i + 1]) << 8);
  }
}
// initialise and start everything
void setup() 
{
  Wire.begin();
  Serial.begin(9600);
  for(int i=0; i<3; ++i) 
  {
    accelerometer_data[i]  = 0;
  }
  init_adxl345();
}

void loop() 
{
  read_adxl345();
  Serial.print("ACCEL: ");
  Serial.print(float(accelerometer_data[0])*3.9/1000);//3.9mg/LSB scale factor in 13-bit mode
 Serial.print("\t");
  Serial.print(float(accelerometer_data[1])*3.9/1000);
  Serial.print("\t");
  Serial.print(float(accelerometer_data[2])*3.9/1000);
  Serial.print("\n");
  delay(100);
}

6. Result

Open the Serial monitor to see the 3-axis acceleration data. See changes as you sway the Accelerometer.