int led=9;
int brightness=0;
int fadeAmount=5;



void setup() 

{
  // put your setup code here, to run once:
pinMode(led, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
analogWrite(led,brightness);

brightness=brightness+fadeAmount;
  if (brightness <= 0 || brightness >= 255) {

  fadeAmount=-fadeAmount;
}

delay(20);
}