void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  #define LED_PIN 12

  pinMode(12, OUTPUT);
  Serial.begin(115200);
  Serial.println("Welcome to the Serial Playground!");
  Serial.println("---------------------------------");
}

// the loop function runs over and over again forever
  byte value = 0;
void loop() {
  digitalWrite(12, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(12, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
  Serial.print("Counter: ");
  Serial.print(value);
  Serial.print(", hex: ");
  Serial.println(value, HEX);
  value += 1;
  delay(500);
}