While waiting for our big LED matrix, we decided that we would try it with only one to begin with. This was, without a doubt, our hardest step, we spent more than 10 hours on this, we tried many codes, and we downloaded many libraries, but nothing seemed to work the way we wanted it to. We were almost discouraged, and wondered if we should change our project and do something more our speed. But we kept trying, and finally we managed to have a code that works and that does what we wants it to do ( with the help of this website ). Now we have to change it to accommodate our 3x8x32 LED matrix instead of a simple 8x8.

#include <LedControl.h>
#include <Wire.h>


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

int MATRIX_WIDTH = 8;
LedControl lc = LedControl(12, 11, 10, 1); // DIN, CLK, CS, NRDEV
unsigned long delaytime = 50;
int x_key = A1;
int y_key = A0;
int x_pos;
int y_pos;


// object that represents a single light location
// future update with gravity
class Grain
{
  public:
    int x = 0;
    int y = 0;
    int mass = 1;
};
Grain *g;


void setup()
{
  // set up a grain object
  g = new Grain();

  ClearDisplay();

  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()
{
  // The first axis-acceleration-data register
  int regAddress = 0x32;
  int x, y, z;

  readFrom(DEVICE, regAddress, TO_READ, buff); //read the acceleration data from ADXL345

  // Combine the two bytes of each direction
  // Least significant bit first
  x = (((int)buff[1]) << 8) | buff[0];
  y = (((int)buff[3]) << 8) | buff[2];
  z = (((int)buff[5]) << 8) | buff[4];

  // Convert the values into values that can be represented on the matrix
  x = map(x, -300, 300, 0, 8);
  y = map(y, -300, 300, 0, 8);
  z = map(z, -300, 300, 0, 8);

  //we send the x y z values as a string to the serial port
  Serial.print("X: ");
  Serial.print(x);
  Serial.print("   Y: ");
  Serial.print(y);
  Serial.print("   Z: ");
  Serial.print(z);
  Serial.print("\n");

  ClearDisplay();
  // assign the grain to this location
  g->x = x;
  g->y = y;
  lc.setLed(0, g->x, g->y, true);


  //add some delay between each update
  delay(10);
}


void ClearDisplay()
{
  // sets up the lcd display
  int devices = lc.getDeviceCount();

  for (int address = 0; address < devices; address++)
  {
    lc.shutdown(address, false);
    lc.setIntensity(address, 1);
    lc.clearDisplay(address);
  }
}


//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
}