//  Example 05: Turn on LED when the button is pressed 
//  and keep it on after it is released
//  including simple de-bouncing.
//  If the button is held, brightness changes. 
//
// Copy and paste this example into an empty Arduino sketch

#define LED 9     // the pin for the LED 
#define BUTTON 7  // input pin of the pushbutton

int val = 0;      // stores the state of the input pin

int old_val = 0;  // stores the previous value of "val" 
int state = 0;    // 0 = LED off while 1 = LED on

int brightness = 128;        // Stores the brightness value
unsigned long startTime = 0; // when did we begin pressing?

void setup() { 
  pinMode(LED, OUTPUT);   // tell Arduino LED is an output 
  pinMode(BUTTON, INPUT); // and BUTTON is an input 
} 

void loop() {
 
  val = digitalRead(BUTTON); // read input value and store it 
                             // yum, fresh 

  // check if there was a transition 
  if ((val == HIGH) && (old_val == LOW)) {
 
    state = 1 - state; // change the state from off to on
                       // or vice-versa

    startTime = millis(); // millis() is the Arduino clock
                          // it returns how many milliseconds
                          // have passed since the board has
                          // been reset.

    // (this line remembers when the button
    // was last pressed)
    delay(10);
  }

  
// check whether the button is being held down 
  if ((val == HIGH) && (old_val == HIGH)) {

    // If the button is held for more than 500ms.
    if (state == 1 && (millis() - startTime) > 500) {

      brightness++; // increment brightness by 1
      delay(10);    // delay to avoid brightness going
                    // up too fast

      if (brightness > 255) { // 255 is the max brightness

        brightness = 0; // if we go over 255
                        // let’s go back to 0
      }
    }
  }

  old_val = val; // val is now old, let’s store it 

  if (state == 1) {      
    analogWrite(LED, brightness); // turn LED ON at the                                               // current brightness level
  } else { 
    analogWrite(LED, 0); // turn LED OFF 
  } 
}