/*
  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
*/

// Define the button and LED pin numbers
#define buttonPin 2
#define ledPin    5

bool reset; // Flag to indicate if a reset is needed

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);   // Set button pin as input with internal pull-up resistor
  pinMode(ledPin, OUTPUT);            // Set LED pin as output
  pinMode(LED_BUILTIN, OUTPUT);       // Set built-in LED pin as output
  attachInterrupt(digitalPinToInterrupt(buttonPin), ISR_BUTTON, FALLING); // Attach interrupt for button press
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);  // Turn built-in LED on
  digitalWrite(ledPin, HIGH);       // Turn LED on
  delay(1000);                      // Delay 1000 ms
  digitalWrite(LED_BUILTIN, LOW);   // Turn built-in LED off
  digitalWrite(ledPin, LOW);        // Turn LED off
  delay(1000);                      // Delay 1000 ms
}

void yield() {
  if (reset) {                      // Check if a reset is needed
    digitalWrite(ledPin, LOW);      // Turn LED off
    reset = false;                  // Clear the reset flag
  }
}

void ISR_BUTTON() {
  reset = true;                     // Set the flag to indicate that a reset is needed when the button is pressed
}