PDM Unit

This is the driver library of PDM Unit, which is provides a set of methods to control the PDM microphone. Through the I2S interface, the module can record audio data and save it as WAV files.

Support the following products:

UiFlow2 Example

record voice and play voice

Open the pdm_cores3_example.m5f2 project in UiFlow2.

This example records voice and plays voice.

UiFlow2 Code Block:

Example output:

None

MicroPython Example

record voice and play voice

This example records voice and plays voice.

MicroPython Code Block:

# SPDX-FileCopyrightText: 2024 M5Stack Technology CO LTD
#
# SPDX-License-Identifier: MIT

import os, sys, io
import M5
from M5 import *
from unit import PDMUnit
import time


label0 = None
title0 = None
pdm_0 = None


rec_data = None


def setup():
    global label0, title0, pdm_0, rec_data

    M5.begin()
    Widgets.fillScreen(0x222222)
    label0 = Widgets.Label("label0", 128, 114, 1.0, 0xFFFFFF, 0x222222, Widgets.FONTS.DejaVu18)
    title0 = Widgets.Title("PDMUnit CoreS3 Example", 3, 0xFFFFFF, 0x0000FF, Widgets.FONTS.DejaVu18)

    pdm_0 = PDMUnit((1, 2), i2s_port=2, sample_rate=44100)
    Speaker.begin()
    Speaker.setVolumePercentage(1)
    Speaker.end()
    pdm_0.begin()
    rec_data = bytearray(44100 * 10)
    label0.setText(str("rec..."))
    pdm_0.record(rec_data, _, False)
    time.sleep_ms(100)
    while pdm_0.isRecording():
        label0.setText(str("rec..."))
        time.sleep_ms(100)
    pdm_0.end()
    Speaker.begin()
    label0.setText(str("play..."))
    Speaker.playRaw(rec_data, 44100 * 2)
    while Speaker.isPlaying():
        time.sleep_ms(100)
    label0.setText(str("done"))


def loop():
    global label0, title0, pdm_0, rec_data
    M5.update()


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

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

Example output:

None

API

PDMUnit

class unit.pdm.PDMUnit(*args, **kwargs)

Bases: object

PDM Unit class.

Parameters:

• port (list | tuple) – Connect to the PDM Unit.

• i2s_port (int) – I2S port number.

• sample_rate (int) – Sample rate.

UiFlow2 Code Block:

MicroPython Code Block:

from unit import PDMUnit

pdm_0 = PDMUnit((1, 2), i2s_port=0, sample_rate=44100)

begin()

Initialize the PDM microphone.

Returns:

Returns True if initialization was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

pdm.begin()

end()

Stop the PDM microphone.

UiFlow2 Code Block:

MicroPython Code Block:

pdm.end()

record(buffer, sample_rate=16000, stereo=False)

Record audio data into the provided buffer.

Parameters:

• buffer (bytearray) – Buffer to store the recorded audio data

• sample_rate (int) – Sample rate in Hz (default: 16000)

• stereo (bool) – True for stereo recording, False for mono (default: False)

Returns:

True if recording started successfully

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

rec_data = bytearray(16000 * 5)  # 5 seconds buffer
pdm.record(rec_data, 16000, False)

isRecording()

Check if recording is in progress.

Returns:

Returns the number of bytes recorded.

• 0 - Not recording

• 1 - Recording (Queue has available space)

• 2 - Recording (Queue is full)

Return type:

int

UiFlow2 Code Block:

MicroPython Code Block:

pdm.isRecording()

recordWavFile(path, rate=16000, time=5, stereo=False)

Record audio directly to a WAV file.

Parameters:

• path (str) – Path to save the WAV file

• rate (int) – Sample rate in Hz (default: 16000)

• time (int) – Recording duration in seconds (default: 5)

• stereo (bool) – True for stereo recording, False for mono (default: False)

Returns:

True if recording was successful

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

pdm.recordWavFile("/sd/test.wav", 16000, 5, False)

config(**kwargs)

Configure the PDM microphone parameters.

Parameters:

kwargs –

Configuration parameters

• pin_data_in: Data input pin

• pin_ws: Word select pin

• sample_rate: Sample rate in Hz

• stereo: Stereo mode

• over_sampling: Over sampling rate

• noise_filter_level: Noise filter level

• magnification: Audio magnification

• dma_buf_len: DMA buffer length

• dma_buf_count: DMA buffer count

• task_priority: Task priority

• task_pinned_core: Task core pinning

• i2s_port: I2S port number

UiFlow2 Code Block:

MicroPython Code Block:

pdm.config(
    dma_buf_count=3,
    dma_buf_len=256,
    over_sampling=2,
    noise_filter_level=0,
    sample_rate=16000,
    pin_data_in=1,
    pin_ws=2,
    pin_bck=-1,
    pin_mck=-1,
    use_adc=False,
    stereo=False,
    magnification=1,
    task_priority=2,
    task_pinned_core=255,
    i2s_port=i2s_port,
)