/*
  Arduino Forum
  Topics:       Delay() in main loop preventing ISR button detection
  Sub-Category: Programming Questions
  Category:     Using Arduino
  Link:         https://forum.arduino.cc/t/delay-in-main-loop-preventing-isr-button-detection/1148422/14
*/

const byte buttonPin = 2;
const byte pressed   = LOW;
const byte unPressed = HIGH;

const byte ledPin    = 5;

unsigned long myBlinkTimer;
unsigned long myDebounceTimer;

boolean myLedState = LOW;
boolean ledpinActive = true;

void setup() {
  Serial.begin(115200);
  Serial.println("Setup-Start");

  digitalWrite(ledPin, LOW);
  digitalWrite(LED_BUILTIN, LOW);

  pinMode(buttonPin, INPUT_PULLUP);   // Button Pin Mode
  pinMode(ledPin, OUTPUT);            // LED Pin Mode
  pinMode(LED_BUILTIN, OUTPUT);       // LED_BUILTIN Pin Mode
}


void loop() {
   
  ledpinActive = GetToggleSwitchState(buttonPin); 

  // check if 1005 milliseconds have passed by
  if ( TimePeriodIsOver(myBlinkTimer,1005) ) {
    // when REALLY 1005 milliseconds HAVE passed by
    if (myLedState == LOW) {
      myLedState = HIGH; // invert from LOW to HIGH
    }
    else {
      myLedState = LOW; // invert from HIGH to LOW
    }
  }

  digitalWrite(LED_BUILTIN, myLedState); // switch LED On/Off

  // check if ledpin shall be switched on/off
  if (ledpinActive == true) {
    // only in case ledpinActive 
    digitalWrite(ledPin, myLedState); // switch LED on/off
  }
  else {
    digitalWrite(ledPin, LOW); // keep LED off
  }
}


// easy to use helper-function for non-blocking timing
boolean TimePeriodIsOver (unsigned long &startOfPeriod, unsigned long TimePeriod) {
  unsigned long currentMillis  = millis();
  if ( currentMillis - startOfPeriod >= TimePeriod ) {
    // more time than TimePeriod has elapsed since last time if-condition was true
    startOfPeriod = currentMillis; // a new period starts right here so set new starttime
    return true;
  }
  else return false;            // actual TimePeriod is NOT yet over
}


bool GetToggleSwitchState(byte pinNumber) {
  // "static" makes variables persistant over function calls
  static bool toggleState     = false;
  static bool lastToggleState = false;

  static byte buttonStateOld = unPressed;
  static unsigned long buttonScanStarted  =  0;
  unsigned long buttonDebounceTime = 50;
  static unsigned long buttonDebounceTimer;

  byte buttonStateNew;

  if ( TimePeriodIsOver(buttonDebounceTimer, buttonDebounceTime) ) {
    // if more time than buttonDebounceTime has passed by
    // this means let pass by some time until
    // bouncing of the button is over
    buttonStateNew = digitalRead(pinNumber);

    if (buttonStateNew != buttonStateOld) {
      // if button-state has changed
      buttonStateOld = buttonStateNew;
      if (buttonStateNew == unPressed) {
        // if button is released
        toggleState = !toggleState; // toggle state-variable
      } // the attention-mark is the NOT operator
    }   // which simply inverts the boolean state
  }     // !true  = false   NOT true  is false
  //       !false = true    NOT false is true
  return toggleState;
}