#define LED_PIN 16

void setup()
{
  pinMode(LED_PIN, OUTPUT);
}

void loop()
{
  for(int dutycycle = 0; dutycycle<=255 ; dutycycle++)
  {
    analogWrite(LED_PIN,dutycycle);
    delay(10);
  }
  for(int dutycycle = 255; dutycycle>=0 ; dutycycle--)
  {
    analogWrite(LED_PIN,dutycycle);
    delay(10);
  }
}