/*
  BlinkWithoutDelayMore -- Blink without Delay for more LEDs, using Functions

  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.

  State diagram: tinyurl.com/BWODMdiag 

  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
  modified by 7 Mar 2023
  by David Forrest

  This example code is in the public domain.

  For a tutorial on how this works, please read:
  https://www.arduino.cc/en/Tutorial/BuiltInExamples/BlinkWithoutDelay

  Simulation: https://wokwi.com/projects/358554786853847041

  This was written for the discussion at
  https://forum.arduino.cc/t/the-fact-that-something-has-been-used-for-a-long-time-is-in-no-way-an-argument-for-making-it-the-same-for-another-100-years/1097951/24
  on improving the BlinkWithoutDelay example.

  For other ways of doing multiple things at once please read:
  https://forum.arduino.cc/t/flashing-multiple-leds-at-the-same-time/1065564/
  https://learn.adafruit.com/multi-tasking-the-arduino-part-1/now-for-two-at-once


*/

// constants won't change. Used here to set a pin number:
const int ledPin = LED_BUILTIN;  // the number of the LED pin
const int ledPin2 = 3; // the number of the second LED pin

// Variables will change:
int ledState = LOW;  // ledState used to set the LED

// 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

// constants won't change:
const long interval = 1000;  // interval at which to blink (milliseconds)

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

void loop() {
  // here is where you'd put code that needs to be running all the time.

  checkIfItIsTimeToBlinkAndDoIt();  
  // ^^ this function separates the BlinkWithoutDelay core
  // into a function

  checkIfItIsTimeToBlinkAndDoIt_variable(771);  // function handles a separate LED
}

/////// 

void checkIfItIsTimeToBlinkAndDoIt() {
  // 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.  

  // save the current time
  unsigned long currentMillis = millis();

  // test if it is time yet
  if (currentMillis - previousMillis >= interval) {
    // save the last time you changed the LED
    previousMillis = currentMillis;

    // Toggle the ledState variable:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }
    // set the LED output to match the ledState variable:
    digitalWrite(ledPin, ledState);
  } // end interval check

}

void checkIfItIsTimeToBlinkAndDoIt_variable(unsigned long interval) {
  // 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.
  // If it is not yet time it immediately returns control back to loop()

  // These "local scope" variables mask variables of the same name in other scopes
  // this helps keep the global namespace cleaner and easier to maintain
  const int ledPin = ledPin2 ; // copy from global constant
  // use static for private state variables that will persist across calls
  static bool initialized = false;
  static int ledState = LOW;
  static unsigned long previousMillis ;

  // save the current time
  unsigned long currentMillis = millis();

  if (initialized == false) {  // 
    ledState = LOW;
    pinMode(ledPin, OUTPUT);
    digitalWrite(ledPin, ledState);
    initialized = true;
    previousMillis = millis();
  }

  // test if it is time yet
  if (currentMillis - previousMillis >= interval) {
    // save the last time you changed the LED
    previousMillis = currentMillis;

    // Toggle the ledState variable:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }
    // set the LED output to match the ledState variable:
    digitalWrite(ledPin, ledState);
  } // end interval check

}