int led = 0;          
int brightness = 0;   
int fadeAmount = 5;   


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


void loop() {

  analogWrite(led, brightness);


  brightness = brightness + fadeAmount;


  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
 
  delay(30);
}