// Test delays with delays being delays or something like that.
// 30 August 2023, by Koepel, Public Domain.
// Forum: https://forum.arduino.cc/t/delaymicroseconds-is-off-by-an-order-of-magnitude/1163575
// This Wokwi sketch: https://wokwi.com/projects/374490739256465409
//

const int pulsePin = 13;

void setup() 
{
  pinMode(pulsePin, OUTPUT);
} 

void loop() 
{ 
  // -------------------------------------------------
  // Exactly 100 µs by using the clock cycles
  // Result: always 100.000000 µs
  // -------------------------------------------------
  noInterrupts();
  bitSet(PORTB, 7);
  __builtin_avr_delay_cycles(1600-2);  // minus 2 for setting the pin
  bitClear(PORTB, 7);
  interrupts();
  delay(1);

  // -------------------------------------------------
  // The common AVR delay
  // Result: 105.313 µs
  // -------------------------------------------------
  noInterrupts();
  digitalWrite(pulsePin, HIGH);
  _delay_us(100);
  digitalWrite(pulsePin, LOW);
  interrupts();
  delay(1);


  // -------------------------------------------------
  // The Arduino delayMicroseconds
  // Result: 104.062 µs
  // -------------------------------------------------
  noInterrupts();
  digitalWrite(pulsePin, HIGH);
  delayMicroseconds(100);
  digitalWrite(pulsePin, LOW);
  interrupts();
  delay(1);

  delay(10);       // extra delay to easily identify the three pulses
}