void setup() {
  // put your setup code here, to run once:
 pinMode(6, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  int i;
  for(i=0;i<255;i++)
  {
  analogWrite(6,i);
  delay(10);
  }
  for(i=255;i>0;i--)
  {
  analogWrite(6,i);
  delay(10);
  }

}