ESP32 Buzzer Simulator: Wiring, Code and a Live Circuit
This is a passive piezo buzzer wired to an ESP32 DevKit, playing a four-note arpeggio with tone() live in your browser. The simulated piezo measures the frequency on its legs, so a wrong note is a wrong number.
Two wires: GPIO 13 (D13) to the buzzer’s plus side and GND to the other. No library is needed.
- 3.3 V logic
- No library: tone()
- Signal on GPIO 13 (D13)
- Passive piezo
Wiring the Buzzer to the ESP32
Every connection in the circuit above, with the board’s own pin names.
| Buzzer pin | ESP32 pin | Why |
|---|---|---|
| Pin 1 | GPIO 13 (D13) | tone() puts a square wave at the note’s frequency on this pin. |
| Pin 2 | GND | Ground. A passive piezo has no polarity. |
A small passive piezo runs straight from a 3.3 V pin; it is quieter than at 5 V. On an ESP32 DevKit tone() makes the square wave in hardware (LEDC), so the core is free while a note plays. A magnetic buzzer draws more than a pin should give, so drive one through a transistor.
Pins to leave alone on the ESP32
GPIO 34, 35, 36 (VP) and 39 (VN) are input only: they cannot drive a pin or take an internal pull-up. GPIO 0, 2, 5, 12 and 15 are strapping pins, read at power-on, and GPIO 6 to 11 are the flash chip.
On a real bench
The thirty-pin DevKit straddles a breadboard with one row of holes free on each side, which is where the Buzzer’s jumpers go. Many ESP32 boards are wider and cover both rows; then use two breadboards side by side. Hold BOOT while uploading if the IDE cannot connect.
The code
The sketch the circuit above runs. Open it in the editor, change a line and press Run: it compiles in your browser.
const int BUZZER_PIN = 13; // GPIO 13 (D13)
// C, E, G, C: an arpeggio, a quarter second a note.
const int NOTES[] = {523, 659, 784, 1047};
void setup() {
Serial.begin(115200);
Serial.println("Playing");
}
void loop() {
for (int i = 0; i < 4; i++) {
tone(BUZZER_PIN, NOTES[i], 200); // returns at once; the note plays on
delay(250);
}
noTone(BUZZER_PIN);
Serial.println("Again");
delay(500);
}
tone(pin, frequency, duration) starts a square wave and returns at once; the note stops on its own after duration milliseconds. That is why the loop still needs delay(250): without it all four notes would start within microseconds of each other.
The frequencies are the notes of a C major arpeggio, from 523 Hz (C5) to 1047 Hz (C6). #include "pitches.h" gives names like NOTE_C5 for the same numbers.
Serial.begin(115200) opens the serial monitor. Serial is UART0 on the USB bridge. ESP32 sketches usually run it at 115200 baud, which this one does.
Common mistakes with the Buzzer on the ESP32
An active buzzer
An active buzzer has its own oscillator and beeps at one pitch whenever it has power, so tone() cannot change its note. For melodies you need a passive one; the two look the same, but the active kind usually has a sticker on top.
No delay between notes
tone() does not wait for the note to finish. Call it twice in a row and only the second note plays. Wait at least as long as the note, as the sketch does.
Putting the buzzer on an input-only pin
GPIO 34, 35, 36 and 39 on the ESP32 have no output driver at all. pinMode() to OUTPUT on one of them does nothing and the line never moves, which looks exactly like a dead part. GPIO 4 (D4) is a safe choice; so are GPIO 13, 14, 16 to 19, 23, 25 to 27 and 32 to 33.
Questions and answers
Can I simulate a buzzer with an ESP32 DevKit?
Yes. The circuit at the top of this page is an ESP32 DevKit with a piezo buzzer, running in your browser on a simulated ESP32 (Xtensa LX6). The simulated piezo reports the frequency it is driven at, and the editor’s scope can show the square wave on the pin. Press Run it in the editor to change the wiring or the code; it is free and needs no account.
Can I play two notes at once?
Not with tone(): it drives one pin at a time. Two buzzers on two pins with your own timing can, or a DFPlayer module for recorded sound.
How do I make it louder?
Drive the piezo from two pins in opposite phase, or through a transistor from a higher voltage. A magnetic buzzer is louder but needs the transistor.
Where do I find the note frequencies?
#include "pitches.h" in the editor gives NOTE_ names from NOTE_B0 (31 Hz) to NOTE_DS8 (4978 Hz), the same list the Arduino toneMelody example uses.
Build your own Buzzer project
Open this circuit in the editor, change the wiring or the code, and keep your version in a free account.