int value = 0; // PWM value
int ledPin = 9; // the LED
int buttonPin = 7; // button with input pullup, tied to ground
int buttonVal; // HIGH or LOW
int dir = 0; // fade direction UP

void setup() {
  Serial.begin(9600);
  Serial.print("  Fade UP ");
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() {
  buttonVal = digitalRead(buttonPin); // read the button

  while (buttonVal == LOW ) { // if button is pressed
    delay(100);
    buttonVal = HIGH;

    if (dir == 0) { // if direction is up, fade to max
      value += 5;
      Serial.print(".");
      analogWrite(ledPin, value); // 0 to 255
      delay(30);

      if (value >= 250) {
        Serial.print("\nFade DOWN ");
        dir = 1;
      }
    }

    if (dir == 1) { // if direction is down, fade to min
      value -= 5;
      Serial.print(".");
      analogWrite(ledPin, value);
      delay(30);

      if (value <= 0) {
        Serial.print("\n  Fade UP ");
        dir = 0;
      }
    }
  }
}