void setup() {
  pinMode(9, OUTPUT); pinMode(10, OUTPUT); pinMode(11, OUTPUT);
}
int j = 1; int a = 0;
void loop() {
  if (a>254) {a = 254; j = -1;} else if (a < 1) {j = 1; a = 1;}
  analogWrite(9, a);analogWrite(10, a);analogWrite(11, a);
  a = a+j;
  delay(100);
}