Chain Buzzer

BuzzerChain is the helper class for buzzer devices on the Chain bus. It provides methods to control buzzer frequency, duty cycle, play modes (auto play, manual play, note play), and play musical notes.

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UiFlow2 Example

Button tone playback

Open the m5core_chain_buzzer_basic_example.m5f2 project in UiFlow2.

This example demonstrates how to use the Chain Buzzer in auto play mode. It initializes the buzzer RGB indicator, then plays 500 Hz, 1000 Hz, or 1500 Hz tones when button A, B, or C is clicked.

UiFlow2 Code Block:

Example output:

None

MicroPython Example

Button tone playback

This example demonstrates how to use the Chain Buzzer in auto play mode. It initializes the buzzer RGB indicator, then plays 500 Hz, 1000 Hz, or 1500 Hz tones when button A, B, or C is clicked.

MicroPython Code Block:

# SPDX-FileCopyrightText: 2026 M5Stack Technology CO LTD
#
# SPDX-License-Identifier: MIT

import os, sys, io
import M5
from M5 import *
from chain import BuzzerChain
from chain import ChainBus


title0 = None
label_freq = None
label_tip = None
bus2 = None
chain_buzzer_0 = None


def btna_was_clicked_event(state):
    global title0, label_freq, label_tip, bus2, chain_buzzer_0
    label_freq.setText(str("Freq: 500 Hz"))
    chain_buzzer_0.tone(500, 50, 100)


def btnb_was_clicked_event(state):
    global title0, label_freq, label_tip, bus2, chain_buzzer_0
    label_freq.setText(str("Freq: 1000 Hz"))
    chain_buzzer_0.tone(1000, 50, 100)


def btnc_was_clicked_event(state):
    global title0, label_freq, label_tip, bus2, chain_buzzer_0
    label_freq.setText(str("Freq: 1500 Hz"))
    chain_buzzer_0.tone(1500, 50, 100)


def setup():
    global title0, label_freq, label_tip, bus2, chain_buzzer_0

    M5.begin()
    Widgets.setRotation(1)
    Widgets.fillScreen(0x000000)
    title0 = Widgets.Title(
        "Chain Buzzer Example", 3, 0xFFFFFF, 0x0000FF, Widgets.FONTS.Montserrat18
    )
    label_freq = Widgets.Label(
        "Freq: -- Hz", 107, 90, 1.0, 0xFFFFFF, 0x000000, Widgets.FONTS.Montserrat18
    )
    label_tip = Widgets.Label(
        "Press button tone", 78, 205, 1.0, 0xFFFFFF, 0x000000, Widgets.FONTS.Montserrat18
    )

    BtnA.setCallback(type=BtnA.CB_TYPE.WAS_CLICKED, cb=btna_was_clicked_event)
    BtnB.setCallback(type=BtnB.CB_TYPE.WAS_CLICKED, cb=btnb_was_clicked_event)
    BtnC.setCallback(type=BtnC.CB_TYPE.WAS_CLICKED, cb=btnc_was_clicked_event)

    bus2 = ChainBus(2, tx=21, rx=22)
    chain_buzzer_0 = BuzzerChain(bus2, 1)
    chain_buzzer_0.tone(2700, 50, 100)
    chain_buzzer_0.set_rgb_color(0x33FFFF)
    chain_buzzer_0.set_rgb_brightness(100, save=False)
    chain_buzzer_0.set_mode(BuzzerChain.MODE_AUTO_PLAY)


def loop():
    global title0, label_freq, label_tip, bus2, chain_buzzer_0
    M5.update()


if __name__ == "__main__":
    try:
        setup()
        while True:
            loop()
    except (Exception, KeyboardInterrupt) as e:
        try:
            bus2.deinit()
            from utility import print_error_msg

            print_error_msg(e)
        except ImportError:
            print("please update to latest firmware")

Example output:

None

API

BuzzerChain

class chain.buzzer.BuzzerChain(bus, device_id)

Bases: KeyChain

Buzzer Chain class for interacting with buzzer devices over Chain bus.

Parameters:

• bus (ChainBus) – The Chain bus instance.

• device_id (int) – The device ID of the buzzer on the Chain bus.

UiFlow2 Code Block:

MicroPython Code Block:

from chain import ChainBus
from chain import BuzzerChain

bus2 = ChainBus(2, tx=21, rx=22)
chain_buzzer_0 = BuzzerChain(bus2, 1)

For other button and some general methods, please refer to the ChainKey class.

set_mode(mode)

Set the buzzer mode.

Parameters:

mode (int) – Buzzer mode. Use BuzzerChain.MODE_AUTO_PLAY (0), BuzzerChain.MODE_MANUAL_PLAY (1), or BuzzerChain.MODE_NOTE_PLAY (2).

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_buzzer_0.set_mode(BuzzerChain.MODE_AUTO_PLAY)

get_mode()

Get the buzzer mode.

Returns:

Buzzer mode. BuzzerChain.MODE_AUTO_PLAY (0), BuzzerChain.MODE_MANUAL_PLAY (1), or BuzzerChain.MODE_NOTE_PLAY (2). Returns None if failed.

Return type:

int

UiFlow2 Code Block:

MicroPython Code Block:

mode = chain_buzzer_0.get_mode()

tone(freq=2700, duty=50, duration_ms=100)

Play tone (only works in AUTO_PLAY mode).

Parameters:

• freq (int) – Frequency in Hz. Range: 100-10000. Default: 2700.

• duty (int) – Duty cycle (0-100). Default: 50.

• duration_ms (int) – Duration in milliseconds. Default: 100.

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_buzzer_0.tone(2700, 50, 1000)
success = chain_buzzer_0.tone()  # Use default values: 2700Hz, 50% duty, 100ms

set_freq(freq=2700)

Set the buzzer frequency.

Parameters:

freq (int) – Frequency in Hz. Range: 100-10000. Default: 2700.

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_buzzer_0.set_freq(2700)
success = chain_buzzer_0.set_freq()  # Use default: 2700Hz

get_freq()

Get the buzzer frequency.

Returns:

Frequency in Hz, or None if failed.

Return type:

int

UiFlow2 Code Block:

MicroPython Code Block:

freq = chain_buzzer_0.get_freq()

set_duty(duty=50)

Set the buzzer duty cycle.

Parameters:

duty (int) – Duty cycle (0-100). Default: 50.

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_buzzer_0.set_duty(50)
success = chain_buzzer_0.set_duty()  # Use default: 50%

get_duty()

Get the buzzer duty cycle.

Returns:

Duty cycle (0-100), or None if failed.

Return type:

int

UiFlow2 Code Block:

MicroPython Code Block:

duty = chain_buzzer_0.get_duty()

set_status(status)

Set the buzzer status (only works in MANUAL_PLAY mode).

Parameters:

status (int) – Buzzer status. Use BuzzerChain.STATUS_OFF (0) or BuzzerChain.STATUS_ON (1).

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_buzzer_0.set_status(BuzzerChain.STATUS_ON)

get_status()

Get the buzzer status.

Returns:

Buzzer status. BuzzerChain.STATUS_OFF (0) or BuzzerChain.STATUS_ON (1). Returns None if failed.

Return type:

int

UiFlow2 Code Block:

MicroPython Code Block:

status = chain_buzzer_0.get_status()

note(note_index, duration_ms=100)

Play note (only works in NOTE_PLAY mode).

Parameters:

• note_index (int) – Note index (0-61). 0 is rest (silence), 13 is C4, and 61 is C8.

• duration_ms (int) – Duration in milliseconds. Default: 100.

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_buzzer_0.note(25, 500)  # Play C5 for 500ms
success = chain_buzzer_0.note(25)  # Play C5 for 100ms (default duration)