// https://wokwi.com/projects/417575942104993793
// Blink Without Delay with Serial.prints() for debugging 
// Based on:
// https://wokwi.com/projects/325771523077964370
// ...but with added Serial.print() for showing processing
// uncomment the Serial.print("L") line to see how fast loop() loops.
// original code modified from
// per https://docs.arduino.cc/built-in-examples/digital/BlinkWithoutDelay/
// Other simulations: https://forum.arduino.cc/t/wokwi-simulations-for-arduino-built-in-examples/1304754

/*
  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.

  https://www.arduino.cc/en/Tutorial/BuiltInExamples/BlinkWithoutDelay
  https://wokwi.com/projects/325771523077964370
*/

// constants won't change. Used here to set a pin number:
const int ledPin =  LED_BUILTIN;// the number of the 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);
  Serial.begin(115200); // Enable serial output for debugging
  Serial.println("s=startup, L=loop, t=timemout, h=high, l=low, w=write");
  Serial.print("s"); // setup
}

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

  // 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.
  unsigned long currentMillis = millis();
  //Serial.print("L"); // loop -- happens too fast, commented out

  if (currentMillis - previousMillis >= interval) {
    Serial.print("t"); // timeout
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      Serial.print("h"); // set high
      ledState = HIGH;
    } else {
      Serial.print("l"); // set low
      ledState = LOW;
    }

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);
    Serial.print("w"); // write
  }
}