A Test Sketch to Evaluate delayMecroseconds() on UNO Rev3 and R4

dms_on_r4_tester.ino

//////////////////////////////////////////////////////////////////////
//
// A Test Sketch to Evaluate delayMecroseconds() on UNO Rev3 and R4
//
// Try this sketch running on both Arduino UNO Rev3 and UNO R4 by the
// following steps.
// 
//   1) Connect the GPIO #12 pin on your Arduino Rev3/R4 to a buzzer
//      and amplify it to listen to the signal from the GPIO pin.
//      (If you have "EK JAPAN SU-1204", just attach it to the Arduino
//       UNO series.)
//   2) Connect the Arduino to your PC.
//   3) Run the Arduino IDE and make it recognize the Arduino.
//   4) Write the following sketch into the IDE and run it on the
//      Arduino.
//   5) Listen to the sound from the buzzer. The sketch plays "Do-Re-Me"
//      continuously. However, only when running it on UNO R4, you can
//      hear a higher sound of "Do-Re-Me" and a lower sound alternately,
//      whereas the same tone of "Do-Re-Me" is played on UNO Rev3 (and
//      other boards, like Raspberry Pi Pico).
//
// I AM THINKING THAT THE "delayMecroseconds()" ON UNO R4 OVERSLEEPS
// A LITTLE MORE THAN THE SPECIFIED DURATION.
//
//
// To make this sketch, I adopted some codes written on the text book
// of "EK JAPAN SU-1204."
//
// Written by @colrichie on 2025-08-07
//
//////////////////////////////////////////////////////////////////////

void setup() {
  pinMode(12,OUTPUT);
}

void loop() {
  // Buzzing with delayMecroseconds()
  for (int i=0; i<528; i++) { // Do
    digitalWrite(12,HIGH);
    delayMecroseconds(473);
    digitalWrite(12,LOW);
    delayMecroseconds(473);
  }
  for (int i=0; i<588; i++) { // Re
    digitalWrite(12,HIGH);
    delayMecroseconds(425);
    digitalWrite(12,LOW);
    delayMecroseconds(425);
  }
  for (int i=0; i<660; i++) { // Me
    digitalWrite(12,HIGH);
    delayMecroseconds(379);
    digitalWrite(12,LOW);
    delayMecroseconds(379);
  }

  // Buzzing with tone()
  tone(12,1056); delay(500);  // Do
  tone(12,1176); delay(500);  // Re
  tone(12,1320); delay(500);  // Me
  noTone(12);
}