CH32V003J4M6 Audio Projects

A collection of audio projects for the CH32V003J4M6 RISC-V microcontroller, demonstrating various audio synthesis and playback techniques on an 8-pin, $0.10 microcontroller. From simple 1-bit music to compressed audio sample playback and speech synthesis. Click on the image to watch a video and hear the results.

Project Overview

This repository contains several firmware projects and development tools:

Firmware Projects

1. SimpleSoundFirmware - Single-voice 1-bit music playback (monophonic)
2. PolyphonicSoundFirmware - Advanced 8-voice polyphonic music with PWM synthesis
3. SamplePlayback - Compressed audio sample playback (IMA ADPCM, QOA, 2-bit ADPCM)
4. Talkie - Speech synthesis using the Talkie library

Development Tools

1. Buzzer Studio - Interactive web app for designing 1-bit sound effects and exporting MIDI tracks

The Buzzer Studio project is available here: https://buzzer-studio.atomic14.com/

A word of warning - the Buzzer Studio codebase was creating with a lot of help from AI tools. It all runs client side, there is no backend for anyone to hack. But the code may not always be easy for a human to understand.

Quick Start

Building the Firmware

All firmware projects build with PlatformIO. To build locally:

Simple Sound Firmware (1-bit monophonic):

cd SimpleSoundFirmware
pio run

Polyphonic Sound Firmware (8-voice PWM):

cd PolyphonicSoundFirmware
pio run

Sample Playback (compressed audio):

cd SamplePlayback
pio run

Talkie (speech synthesis):

cd Talkie
pio run

For detailed firmware information, see each project's README: - SimpleSoundFirmware/README.md - Original single-voice 1-bit music - PolyphonicSoundFirmware/README.md - 8-voice polyphonic synthesis - SamplePlayback/README.md - Compressed audio playback with multiple codecs - Talkie/README.md - Speech synthesis implementation

Converting Music Files and Creating Sound Effects

Buzzer Studio (Web App):

cd buzzer-studio
npm install
npm run dev

The app allows you to: - Export tracks from MIDI files for 1-bit playback - Design sound effects with real-time preview - Export to C arrays for microcontrollers - Export to Python for MicroPython/CircuitPython - Choose from preset effects (jump, coin, laser, etc.) - Play LPC encoded audio - Encode WAV files to LPC

Hardware Requirements

• Microcontroller: CH32V003J4M6 (RISC-V, 8-pin SOIC)
• Power: 3.3V supply
• Programming: WCH-Link or compatible programmer

Pin Configurations

SimpleSoundFirmware (1-bit music): - Output: Piezo buzzer or small speaker (connected to PD6) - Input: Trigger button or signal (connected to PC1)

PolyphonicSoundFirmware (8-voice music): - Output: Piezo buzzer or small speaker (connected to PA1) - No trigger input: Plays automatically on startup

SamplePlayback (compressed audio): - Output: PWM audio output on PA1 (8-bit via PWM) - No trigger input: Plays automatically on startup

Talkie (speech synthesis): - Output: PWM audio output on PA1 (8-bit via PWM) - No trigger input: Plays speech on startup

Project Structure

brain-transplant/
├── SimpleSoundFirmware/      # 1-bit monophonic music playback
│   ├── src/                  # Source code (main.cpp, music data)
│   ├── platformio.ini        # Build configuration
│   └── README.md             # Documentation
│
├── PolyphonicSoundFirmware/  # 8-voice polyphonic music
│   ├── src/                  # Source code (polyphonic player)
│   ├── platformio.ini        # Build configuration
│   └── README.md             # Documentation
│
├── SamplePlayback/           # Compressed audio sample playback
│   ├── src/                  # Source code (ADPCM decoders, PWM player)
│   │   ├── AudioStream.h     # Base interface for codecs
│   │   ├── IMAAdpcmStream.*  # IMA ADPCM decoder
│   │   ├── ADPCM2BitStream.* # 2-bit ADPCM decoder
│   │   ├── player.*          # PWM playback engine
│   │   └── audio/            # Audio data files
│   ├── platformio.ini        # Build configuration
│   └── README.md             # Documentation
│
├── Talkie/                   # Speech synthesis
│   ├── src/                  # Source code (Talkie library port)
│   │   ├── Talkie.*          # Speech synthesis engine
│   │   ├── phrases.*         # Pre-defined speech phrases
│   │   └── player.*          # Audio playback
│   ├── platformio.ini        # Build configuration
│   └── README.md             # Documentation
│
├── scripts/                  # Python audio conversion tools
│   ├── wav_to_adpcm_c.py     # WAV → ADPCM C array converter
│   ├── adpcm_2bit_decoder.py # 2-bit ADPCM decoder
│   ├── compare_audio.py      # Audio comparison tools
│   ├── pyproject.toml        # Python dependencies (uv)
│   └── README.md             # Scripts documentation
│
├── buzzer-studio/            # Interactive web app
│   ├── src/                  # TypeScript source code
│   ├── public/               # Static assets
│   ├── index.html            # App entry point
│   ├── package.json          # Dependencies and scripts
│   └── README.md             # App documentation
│
└── .github/
    └── workflows/
        ├── build-firmware.yml      # Firmware CI/CD
        └── buzzer-studio-ci.yml    # Buzzer Studio CI/CD

Documentation

Firmware Projects

• SimpleSoundFirmware - 1-bit monophonic music playback
• PolyphonicSoundFirmware - 8-voice polyphonic synthesis
• SamplePlayback - Compressed audio playback with multiple codec support
• Talkie - Speech synthesis implementation

Development Tools

• Buzzer Studio - Web app for designing 1-bit sound effects and exporting MIDI
• Scripts - Python tools for audio conversion and ADPCM encoding

Development

Prerequisites

For Firmware Development: - PlatformIO - Embedded build system - CH32V platform support (installed automatically by PlatformIO) - WCH-Link programmer (or compatible)

For Buzzer Studio App: - Node.js 18+ and npm - Modern web browser with Web Audio API support

For Python Scripts: - Python 3.8+ - uv package manager

How It Works

Firmware Approaches

SimpleSoundFirmware (1-bit music): 1. Waits for trigger signal on pin PC1 2. Toggles output pin (PD6) at specified frequencies 3. Uses microsecond-precision delays for accurate timing 4. Simple 1-bit audio (square wave)

PolyphonicSoundFirmware (8-voice music): 1. Automatically starts on power-up 2. Manages up to 8 simultaneous voices using PWM synthesis 3. Outputs mixed audio through PA1 at 8 kHz sample rate 4. Software mixing with real-time voice generation

SamplePlayback (compressed audio): 1. Decodes compressed audio using codec decoders (IMA ADPCM, 2-bit ADPCM) 2. Outputs 8-bit audio via PWM on PA1 at 8 kHz 3. Supports multiple codec formats with extensible architecture 4. Compression ratios of 2:1 and 4:1

Talkie (speech synthesis): 1. Uses Linear Predictive Coding (LPC) for speech synthesis 2. Pre-defined vocabulary of phonemes and words 3. Outputs synthesized speech via PWM on PA1 4. Real-time speech generation from phrase data