Note

Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts.

Why Join?

• Expert Support: Solve post-sale issues and technical challenges with help from our community and team.

• Learn & Share: Exchange tips and tutorials to enhance your skills.

• Exclusive Previews: Get early access to new product announcements and sneak peeks.

• Special Discounts: Enjoy exclusive discounts on our newest products.

• Festive Promotions and Giveaways: Take part in giveaways and holiday promotions.

👉 Ready to explore and create with us? Click [here] and join today!

3.2 Play Custom Tones with a Passive Buzzer

In this lesson, we’ll learn how to use a passive buzzer with the Raspberry Pi Pico 2 to play different tones and even simple melodies! Unlike an active buzzer, a passive buzzer needs a changing electrical signal to produce sound, which means we can control the pitch of the sound by changing the signal’s frequency.

What You’ll Need

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
Newton Lab Kit	450+	Newton Lab Kit

You can also buy them separately from the links below.

SN	COMPONENT	QUANTITY	LINK
1	Raspberry Pi Pico 2	1	BUY
2	Micro USB Cable	1
3	Breadboard	1	BUY
4	Jumper Wires	Several	BUY
5	Transistor	1(S8050)	BUY
6	Resistor	1(1KΩ)	BUY
7	Passive Buzzer	1	BUY

Understanding the Passive Buzzer

A passive buzzer works like a tiny speaker. It doesn’t produce sound on its own; instead, it needs an oscillating signal to make sound. By providing signals of different frequencies, we can make the buzzer produce different pitches, allowing us to play notes and melodies.

Circuit Diagram

In this circuit, the passive buzzer is powered through a transistor (S8050 NPN). The transistor amplifies the current, making the buzzer sound louder than if it were connected directly to the Pico.

Here’s what happens:

• GP15 outputs a high signal to control the transistor.

• When the transistor is activated, it allows current to flow through the buzzer, making it beep.

A 1kΩ resistor is used to limit the current to protect the transistor.

Wiring Diagram

Make sure you are using the passive buzzer. You can tell it’s the correct one by looking for the exposed PCB (as opposed to the sealed back, which is a active buzzer).

Writing the Code

Now, let’s write some code to make the buzzer play different tones.

Note

• Open the 3.2_custom_tone.py from newton-lab-kit/micropython or copy the code into Thonny, then click “Run” or press F5.

• Ensure the correct interpreter is selected: MicroPython (Raspberry Pi Pico).COMxx.

import machine
import utime

# Initialize PWM on GP15
buzzer = machine.PWM(machine.Pin(15))

def play_tone(frequency, duration):
    # Set the frequency of the PWM signal
    buzzer.freq(frequency)
    # Set duty cycle to 50%
    buzzer.duty_u16(32768)
    # Play the tone for the specified duration
    utime.sleep_ms(duration)
    # Turn off the buzzer
    buzzer.duty_u16(0)

# Play some tones
play_tone(440, 500)  # A4 note for 500ms
utime.sleep_ms(200)
play_tone(494, 500)  # B4 note for 500ms
utime.sleep_ms(200)
play_tone(523, 500)  # C5 note for 500ms

When the code runs, you will hear the passive buzzer play the A4 note for 500ms, the B4 note for 500ms, and the C5 note for 500ms respectively.

Explanation of the Code

1. Initialize PWM:

   • buzzer = machine.PWM(machine.Pin(15)): This sets up PWM (Pulse Width Modulation) on pin GP15, which we’ll use to control the buzzer.

2. Define the play_tone Function:

   def play_tone(frequency, duration):
       buzzer.freq(frequency)
       buzzer.duty_u16(32768)
       utime.sleep_ms(duration)
       buzzer.duty_u16(0)
   

   • frequency: The pitch of the tone. Higher frequency means a higher pitch.

   • duration: How long the tone plays, in milliseconds.

   • buzzer.duty_u16(32768): Sets the duty cycle to 50% (half of 65535), which is ideal for generating sound.

   • After the duration, we turn off the buzzer by setting the duty cycle to 0.

3. Play Notes:

   We call play_tone with different frequencies corresponding to musical notes.

   # Play some tones
   play_tone(440, 500)  # A4 note for 500ms
   utime.sleep_ms(200)
   play_tone(494, 500)  # B4 note for 500ms
   utime.sleep_ms(200)
   play_tone(523, 500)  # C5 note for 500ms
   

Playing a Melody

Now that we’ve learned how to play individual tones with the passive buzzer, let’s create a simple melody! This will help us understand how to sequence notes and control their durations to produce music.

import machine
import utime

# Note frequencies (in Hz)
NOTE_C4 = 262
NOTE_D4 = 294
NOTE_E4 = 330
NOTE_F4 = 349
NOTE_G4 = 392
NOTE_A4 = 440
NOTE_B4 = 494
NOTE_C5 = 523

melody = [
    NOTE_C4, NOTE_D4, NOTE_E4, NOTE_F4,
    NOTE_G4, NOTE_A4, NOTE_B4, NOTE_C5
]

note_durations = [
    500, 500, 500, 500,
    500, 500, 500, 500
]

# Initialize PWM on GP15
buzzer = machine.PWM(machine.Pin(15))

def play_tone(frequency, duration):
    buzzer.freq(frequency)
    buzzer.duty_u16(32768)
    utime.sleep_ms(duration)
    buzzer.duty_u16(0)
    utime.sleep_ms(50)  # Short pause between notes

for i in range(len(melody)):
    play_tone(melody[i], note_durations[i])

When you run this code, the buzzer will play a simple melody by sounding each note in the sequence. Each note lasts for 500 milliseconds, and there’s a short pause between notes. You’ll hear the buzzer play an ascending scale from Middle C (C4) up to the next octave’s C (C5).

Experimenting Further

• Create Your Own Melody: Change the notes and durations in the melody and note_durations lists to compose your own tune.

• Adjust the Tempo: Modify the values in note_durations to speed up or slow down the melody.

• Add More Notes: Define additional notes by adding their frequencies and include them in your melody.

• Change the Volume: Adjust the duty cycle in buzzer.duty_u16() to make the buzzer louder or quieter. A value around 32768 gives 50% duty cycle.

Conclusion

In this lesson, you’ve learned how to use a passive buzzer to play tones and melodies with the Raspberry Pi Pico 2. By controlling the frequency of the PWM signal, you can create a variety of sounds and even play simple songs. This is a great way to add audio feedback or fun musical elements to your projects.