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3.2 Custom Tone

We have used active buzzer in the previous project, this time we will use passive buzzer.

Like the active buzzer, the passive buzzer also uses the phenomenon of electromagnetic induction to work. The difference is that a passive buzzer does not have oscillating source, so it will not beep if DC signals are used. But this allows the passive buzzer to adjust its own oscillation frequency and can emit different notes such as “doh, re, mi, fa, sol, la, ti”.

Let the passive buzzer emit a melody!

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
ESP32 Starter Kit	320+	ESP32 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
ESP32 Board	BUY
ESP32 Camera Extension	BUY
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
Buzzer	-
Transistor	BUY

Available Pins

Here is a list of available pins on the ESP32 board for this project.

Available Pins

IO13, IO12, IO14, IO27, IO26, IO25, IO33, IO32, IO15, IO2, IO0, IO4, IO5, IO18, IO19, IO21, IO22, IO23

Schematic

When the IO14 output is high, after the 1K current limiting resistor (to protect the transistor), the S8050 (NPN transistor) will conduct, so that the buzzer will sound.

The role of S8050 (NPN transistor) is to amplify the current and make the buzzer sound louder. In fact, you can also connect the buzzer directly to IO14, but you will find that the buzzer sound is smaller.

Wiring

Two types of buzzers are included in the kit. We need to use passive buzzer. Turn them around, the exposed PCB is the one we want.

The buzzer needs to use a transistor when working, here we use S8050 (NPN Transistor).

Code

Note

• Open the 3.2_custom_tone.ino file under the path of esp32-starter-kit-main\c\codes\3.2_custom_tone.

• After selecting the board (ESP32 Dev Module) and the appropriate port, click the Upload button.

• Always displaying “Unknown COMxx”?

After the code is successfully uploaded, you will hear the passive buzzer play a sequence of 7 musical notes.

How it works?

1. Define constants for the buzzer pin and PWM resolution.

   const int buzzerPin = 14; //buzzer pin
   const int resolution = 8;
   

2. Define an array containing the frequencies of the 7 musical notes in Hz.

   int frequencies[] = {262, 294, 330, 349, 392, 440, 494};
   

3. Create a function to play a given frequency on the buzzer for a specified duration.

   void playFrequency(int frequency, int duration) {
       ledcWriteTone(buzzerPin, frequency); // Start the tone
       delay(duration); // Wait for the specified duration
       ledcWriteTone(buzzerPin, 0); // Stop the buzzer
   }
   

   • uint32_t ledcWriteTone(uint8_t pin, uint32_t freq);: This function is used to setup the pin to 50 % PWM tone on selected frequency.

     • pin select LEDC pin.

     • freq select frequency of pwm signal.

   This function will return frequency set for channel. If 0 is returned, error occurs and ledc cahnnel was not configured.

4. Configure the PWM channel and attach the buzzer pin in the setup() function.

   void setup() {
       ledcAttach(buzzerPin, 2000, resolution); // Set up the PWM pin
   }
   

   • bool ledcAttach(uint8_t pin, uint32_t freq, uint8_t resolution);: This function is used to setup LEDC pin with given frequency and resolution. LEDC channel will be selected automatically.

     • pin select GPIO pin.

     • freq select frequency of pwm.

     • resolution_bits select resolution for ledc channel. Range is 1-14 bits (1-20 bits for ESP32).

5. In the loop() function, play the sequence of 7 notes with a brief pause between each note and a 1-second pause before repeating the sequence.

   void loop() {
       for (int i = 0; i < 7; i++) {
           playFrequency(frequencies[i], 300); // Play each note for 300ms
           delay(50); // Add a brief pause between the notes
       }
       delay(1000); // Wait for 1 second before replaying the sequence
   }