 void loop()
 {
   toggle = !toggle;
-  digitalWrite(13, toggle);
+  digitalWrite(LED_BUILTIN, toggle);
   delay(5000);
 
   Serial.print("Start I2C Bus Scan from ");

void setup()
{
  // Initialize pin 13 as an output - onboard LED.
  pinMode(13, OUTPUT);

  // join i2c bus (address optional for master)
  Wire.begin();

  Serial.begin(115200);
  while(!Serial);
}


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

  I2CBusScan(startAddress, endAddress);

  Serial.println("\ndone");
}
