Text Editor

Adafruit recommends using the Mu editor for editing your CircuitPython code. You can get more info in this guide.

Alternatively, you can use any text editor that saves simple text files.

Download the Project Bundle

Your project will use a specific set of CircuitPython libraries, folder of .wav file assets, and the code.py file. To get everything you need, click on the Download Project Bundle link below, and uncompress the .zip file.

Drag the contents of the uncompressed bundle directory onto your Feather board's CIRCUITPY drive, replacing any existing files or directories with the same names, and adding any new ones that are necessary.

# SPDX-FileCopyrightText: 2022 John Park for Adafruit Industries
# SPDX-License-Identifier: MIT

# Breakbeat Breadboard based on:
# @todbot / Tod Kurt - https://github.com/todbot/plinkykeeb
# Convert files to appropriate WAV format (mono, 22050 Hz, 16-bit signed) with command:
#  sox loop.mp3 -b 16 -c 1 -r 22050 loop.wav
# put samples in "/wav" folder

import time
import board
import keypad
import audiocore
import audiomixer
from audiopwmio import PWMAudioOut as AudioOut

# wait a little bit so USB can stabilize and not glitch audio
time.sleep(3)

# list of (samples to play, mixer gain level)
wav_files = (
    ('wav/amen_22k16b_160bpm.wav', 1.0),
    ('wav/dnb21580_22k16b_160bpm.wav', 0.9),
    ('wav/drumloopA_22k16b_160bpm.wav', 1.0),
    ('wav/femvoc_330662_22k16b_160bpm.wav', 0.8),
    ('wav/scratch3667_4bar_22k16b_160bpm.wav', 0.5),
    ('wav/pt_limor_modem_vox_01.wav', 0.4),
    ('wav/snowpeaks_22k_s16.wav', 0.8),
    ('wav/dnb21580_22k16b_160bpm_rev.wav', 1.0)
)

# pins used by keyboard
KEY_PINS = (
            board.RX, board.D2, board.D3, board.D4,
            board.D5, board.D6, board.D7, board.D8
)

km = keypad.Keys( KEY_PINS, value_when_pressed=False, pull=True)

audio = AudioOut( board.D10 )  # RP2040 PWM, use RC filter on breadboard
mixer = audiomixer.Mixer(voice_count=len(wav_files), sample_rate=22050, channel_count=1,
                         bits_per_sample=16, samples_signed=True)
audio.play(mixer) # attach mixer to audio playback

for i in range(len(wav_files)):  # start all samples at once for use w handle_mixer
    wave = audiocore.WaveFile(open(wav_files[i][0],"rb"))
    mixer.voice[i].play(wave, loop=True)
    mixer.voice[i].level = 0

def handle_mixer(num, pressed):
    voice = mixer.voice[num]   # get mixer voice
    if pressed:
        voice.level = wav_files[num][1]  # play at level in wav_file list
    else: # released
        voice.level = 0  # mute it


while True:
    event = km.events.get()
    if event:
        if event.key_number < len(wav_files):
            if event.pressed:
                handle_mixer(event.key_number, True)

            if event.released:
                handle_mixer( event.key_number, False )

Upload the Code and Libraries to the KB RP2040

After downloading the Project Bundle, plug your KB2040 into the computer USB port. You should see a new flash drive appear in the computer's File Explorer or Finder (depending on your operating system) called CIRCUITPY. Unzip the folder and copy the following items to the KB2040's CIRCUITPY drive. 

  • lib folder
  • wav folder (this contains eight sample loop wav files)
  • code.py

Custom Sample Loops

To create your own loop wav files, convert your audio files to 16-bit mono WAV files at 22KHz sample rate. This guide shows how.

This guide was first published on Mar 19, 2022. It was last updated on Mar 19, 2022.

This page (Code the Breakbeat Breadboard) was last updated on May 15, 2022.

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