int ledPin = 11;
 void setup() {
     // Initilize the digital pin LED_BUILTIN as output
     pinMode(LED_BUILTIN, OUTPUT);
 }
 // The loop() function runs infinitely
 void loop() {
 
     // Fade in
    for(int ledVal = 0; ledVal <= 255; ledVal +=1) {
        analogWrite(ledPin, ledVal);
        delay(15);
    }  

    // Fade out
    for(int ledVal = 255; ledVal >= 0; ledVal -=1) {
        analogWrite(ledPin, ledVal);
         delay(15);
     } 
     
     // Pause for 1 second (1000 milliseconds)
     delay(1000);
 
 }