Introduction

A CircuitPython class to construct a composite synthio wave table from a collection of oscillators. The table is created from a list of oscillator characteristics, sample length, maximum sample value, a lambda factor, and loop smoothing parameters.

Dependencies

This class depends on:

• Adafruit CircuitPython

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle or individual libraries can be installed using circup.

Installing to a Connected CircuitPython Device with Circup

Make sure that you have circup installed in your Python environment. Install it with the following command if necessary:

pip3 install circup

With circup installed and your CircuitPython device connected use the following command to install:

circup install cedargrove_wavebuilder

Or the following command to update an existing version:

circup update

Usage Example

# SPDX-FileCopyrightText: Copyright (c) 2023 JG for Cedar Grove Maker Studios
# SPDX-License-Identifier: MIT

import time
import board
import synthio
import audiobusio
import audiomixer
from cedargrove_wavebuilder import WaveBuilder, WaveShape

# Define synth parameters
SAMPLE_RATE = 22050  # The sample rate in SPS
WAVE_TABLE_LENGTH = 512  # The wave table length in samples
SAMPLE_MAXIMUM = 32700  # The maximum value of a sample

# Define the oscillator wave shape, overtone ratio, and amplitude
tone = [(WaveShape.Sine, 1.0, 0.6)]

# Create the wave table and show the debug messages
wave = WaveBuilder(
    oscillators=tone,
    table_length=WAVE_TABLE_LENGTH,
    sample_max=SAMPLE_MAXIMUM,
    lambda_factor=1.0,
    loop_smoothing=True,
    debug=True,
)

# Define the tone's ADSR envelope parameters
tone_envelope = synthio.Envelope(
    attack_time=0.02 + 0.01,
    attack_level=1.0 * 1.0,
    decay_time=0.0,
    release_time=2.0,
    sustain_level=1.0,
)

# Configure synthesizer for I2S output on a Feather S2
audio_output = audiobusio.I2SOut(
    bit_clock=board.D12, word_select=board.D9, data=board.D6, left_justified=False
)
mixer = audiomixer.Mixer(
    sample_rate=SAMPLE_RATE, buffer_size=4096, voice_count=1, channel_count=1
)
audio_output.play(mixer)
mixer.voice[0].level = 0.50

synth = synthio.Synthesizer(sample_rate=SAMPLE_RATE)
mixer.play(synth)

note_1 = synthio.Note(880, envelope=tone_envelope, waveform=wave.wave_table)

while True:
    # Set the note waveform to sine and play the note
    wave.oscillators = [(WaveShape.Sine, 1.0, 0.6)]
    note_1.waveform = wave.wave_table
    synth.press(note_1)
    synth.release(note_1)
    time.sleep(1)

    # Set the note waveform to square and play the note
    wave.oscillators = [(WaveShape.Saw, 1.0, 0.6)]
    note_1.waveform = wave.wave_table
    synth.press(note_1)
    synth.release(note_1)
    time.sleep(1)

Documentation

API documentation for this library can be found in Cedargrove_WaveBuilder.

For additional detail about WaveBuilder, see Construct a synthio Waveform Object from a List of Oscillators

Attribution: Patch Symbols from PATCH & TWEAK by Kim Bjørn and Chris Meyer, published by Bjooks, are licensed under Creative Commons CC BY-ND 4.0. Some Patch Symbols were modified to create the synthio symbols BlockInput, MixerVoice, Note, Synthesizer, sample, and voice.

Planned Updates

• Add wave table file saving.
• Open external file as the fundamental wave table.
• Include other preset wave types.
• Add examples for filtering and applying synthio.Math to wave tables.

Acknowledgements and Thanks

• Liz Clark, 'Circle of Fifths Euclidean Synth with synthio and CircuitPython' Adafruit Learning Guide for the waveform and noise examples.
• Todd Kurt for essential synthio hints, tricks, and examples (https://github.com/todbot/circuitpython-synthio-tricks).
• Special thanks to Jeff Epler and Adafruit for the comprehensive design and implementation of the CircuitPython synthio module.