// Code from How Fast Does Your Arduino Code Run?
// https://youtu.be/tnfeMCyLZSo

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);

  // Set up Timer 1 to count every single clock cycle
  TCCR1A = 0;
  TCCR1B = 1 << CS10;
  TCNT1 = 0;

  /* Code under test */
  digitalWrite(LED_BUILTIN, HIGH);
  /* End of code under test */

  // Print the result
  unsigned int value = TCNT1;
  Serial.print("Cycles: ");
  Serial.println(value - 1);
  Serial.print("Microseconds: ");
  Serial.println((float)(value - 1) / 16);
}

void loop() {
}