Trying to press a button and toggle an LED flash at 2Hz until i press the button again

Question

i'm trying to learn coding and this has really stumped me so i thought i would ask you lovely people.

basically i'm trying to press a button and have an LED toggle on that is flashing on and off twice in a second, this will be continuous until i press the button again that will turn it off.

here is my code so far.

bool latch = false;

void setup(){
pinMode(1, INPUT);
pinMode(13, OUTPUT);
}
void loop(){
if (digitalRead(1)){
  latch = !latch;
}
if (latch == 1){
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}else{
  digitalWrite(13, LOW)
}
}

Answer 1

Because of the calls to delay(1000), your code requires you to press the button in the exact split-second instant when digitalRead(1) is called. The Arduino cannot listen for button presses while delay() is in action. Also, you call delay(1000) twice, which flashes the LED on and off once in two seconds, not twice in once second.

The solution is to make a counter that counts how many milliseconds have passed since the last time the LED was toggled on or off. The loop will add 1 to counter every millisecond, so that when counter is equal to or greater than 500 (half a second), the LED toggles on or off.

Here is a program that starts blinking the LED (on-and-off in 1 second) when the button is pressed, and stops blinking when the button is pressed again. There are more explanations in the code.

bool latch = false;
bool led_state = false;

// How many milliseconds it has been since the last LED state change
int counter = 0;

void setup() {
  pinMode(2, INPUT);
  pinMode(13, OUTPUT);
}
void loop() {

  // Check if the button was pressed
  if (digitalRead(2)){

    // If the button was pressed, wait half a second before toggling latch,
    // to "de-bounce" the button (prevent it from sending multiple clicks for
    // one press)
    delay(300);
    latch = !latch;
  }

  // If we are in on state (latch == true)...
  if (latch) {

    // ...add 1 to the counter and wait 1 millisecond...
    counter += 1;
    delay(1);

    // ...and toggle the LED state if 500 milliseconds have passed.
    // This we know because counter >= 500.
    if (counter >= 500) {
      if (led_state == true) led_state = false;
      else if (led_state == false) led_state = true;
      counter = 0;
    }
    digitalWrite(13, led_state);

  // If we are in off state, turn the LED off
  } else {
    digitalWrite(13, false);
  }
}