 void setup()
 {
   // Initialize pin 13 as an output - onboard LED.
-  pinMode(13, OUTPUT);
+  pinMode(LED_BUILTIN, OUTPUT);
 
   // join i2c bus (address optional for master)
   Wire.begin();
 
+  // initialize Serial communication
   Serial.begin(115200);
+  // wait for the Serial port to connect. Open the Serial Monitor to continue executing the sketch
   while(!Serial);
 }
 

  Serial.print(endAddress);
  Serial.println(".....");

  I2CBusScan( startAddress, endAddress);

  Serial.println("\ndone");
}

void loop()
{
  toggle = !toggle;
  digitalWrite(LED_BUILTIN, toggle);
  delay(5000);

  Serial.print("Start I2C Bus Scan from ");
