effetto dissolvenza [fade] con arduino

int led = 9;
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);
}