/*
  Blink without Delay

  Turns on and off a light emitting diode (LED) connected to a digital pin,
  without using the delay() function. This means that other code can run at the
  same time without being interrupted by the LED code.

  The circuit:
  - Use the onboard LED.
  - Note: Most Arduinos have an on-board LED you can control. On the UNO, MEGA
    and ZERO it is attached to digital pin 13, on MKR1000 on pin 6. LED_BUILTIN
    is set to the correct LED pin independent of which board is used.
    If you want to know what pin the on-board LED is connected to on your
    Arduino model, check the Technical Specs of your board at:
    https://www.arduino.cc/en/Main/Products

  created 2005
  by David A. Mellis
  modified 8 Feb 2010
  by Paul Stoffregen
  modified 11 Nov 2013
  by Scott Fitzgerald
  modified 9 Jan 2017
  by Arturo Guadalupi

  This example code is in the public domain.

  http://www.arduino.cc/en/Tutorial/BlinkWithoutDelay
*/

//===============================================================================
//DEFINITIONS

// constants:
const int ledPin =  7;// the number of the LED pin
const int buttonPin = 3;     // the number of the pushbutton pin
const long interval = 100;           // interval at which to blink (milliseconds)

// variables:
int ledState = LOW;             // ledState used to set the LED
int buttonState = 0;         // variable for reading the pushbutton status

//===============================================================================
//PROGRAM


void setup() {
  
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);
}


// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0;        // will store last time LED was updated


void loop() {
  // here is where you'd put code that needs to be running all the time.
  
  buttonState = digitalRead(buttonPin);
  
    // check if the pushbutton is pressed. If it is, the buttonState is HIGH:
  if (buttonState == LOW) {
    
    unsigned long currentMillis = millis();

          if (currentMillis - previousMillis >= interval) {
                  // save the last time you blinked the LED
                  previousMillis = currentMillis;
              
                  // if the LED is off turn it on and vice-versa:
                  if (ledState == LOW) {
                    ledState = HIGH;
                  } else {
                    ledState = LOW;
                  }
          }
        
          // check to see if it's time to blink the LED; that is, if the difference
          // between the current time and last time you blinked the LED is bigger than
          // the interval at which you want to blink the LED.
          
            // set the LED with the ledState of the variable:
            digitalWrite(ledPin, ledState);
    } else {
       digitalWrite(ledPin, LOW);
      }
}