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DAFX-to-DaisySP Library

Build and Test License: MIT C++ Standard CMake

A portable DSP algorithm library derived from the DAFX (Digital Audio Effects, 2nd Edition) textbook by Udo Zölzer, targeting the Daisy Seed embedded platform while maintaining complete hardware independence.

Overview

This library bridges the gap between academic DSP algorithms documented in the DAFX textbook and practical embedded audio implementations. It enables developers to deploy professional-grade audio effects on Daisy Seed hardware without being constrained to specific hardware configurations.

Key Features

  • Academic Rigor — Algorithms derived from peer-reviewed DSP textbook with mathematical foundations
  • Hardware Independence — Pure C++ DSP modules work across Daisy Pod, Field, Patch, Petal, or custom designs
  • DaisySP Compatibility — Follows established DaisySP API patterns for seamless integration
  • Real-time Performance — Optimized for ARM Cortex-M7 constraints at 96kHz/24-bit audio
  • Comprehensive Testing — Unit tests with Google Test framework

Implemented Effects

Effects (Virtual Analog)

Effect File Description
Tube Distortion tube.cpp Valve/tube saturation simulation
Wah-Wah wahwah.cpp CryBaby-style wah pedal
Tone Stack tonestack.cpp Amplifier tone controls

Filters

Filter File Description
Low Shelving lowshelving.cpp Bass boost/cut filter
High Shelving highshelving.cpp Treble boost/cut filter
Peak Filter peakfilter.cpp Parametric EQ band

Dynamics

Processor File Description
Noise Gate noisegate.cpp Signal noise reduction

Modulation

Effect File Description
Vibrato vibrato.cpp Pitch modulation effect
Ring Modulator ringmod.cpp Ring modulation synthesis

Spatial

Effect File Description
Stereo Pan stereopan.cpp Stereo panning with multiple laws

Building

Requirements

  • CMake 3.16+
  • C++17 compatible compiler (GCC, Clang, or MSVC)
  • Optional: ARM GCC Toolchain for embedded deployment

Quick Start

# Clone the repository
git clone https://github.com/your-username/DAFX_2_Daisy_lib.git
cd DAFX_2_Daisy_lib

# Build the library
mkdir build && cd build
cmake ..
cmake --build .

# Run tests (optional)
ctest --output-on-failure

Build Options

Option Default Description
BUILD_TESTING ON Build unit tests
BUILD_EXAMPLES ON Build example programs 
# Build without tests
cmake -DBUILD_TESTING=OFF ..

Usage

Basic Example

#include "effects/tube.h"
#include "filters/lowshelving.h"

using namespace daisysp;

// Create effect instances
Tube tube;
LowShelving bass;

void InitEffects(float sample_rate)
{
    // Initialize with sample rate
    tube.Init(sample_rate);
    tube.SetDrive(0.7f);     // 70% drive
    tube.SetBias(0.2f);      // Slight asymmetry
    
    bass.Init(sample_rate);
    bass.SetFrequency(200.0f);  // 200 Hz corner frequency
    bass.SetGain(6.0f);         // +6 dB boost
}

float ProcessSample(float in)
{
    // Chain effects
    float out = tube.Process(in);
    out = bass.Process(out);
    return out;
}

Daisy Hardware Integration

The library is hardware-agnostic — integrate with any Daisy hardware variant:

#include "daisy_pod.h"
#include "effects/tube.h"

daisy::DaisyPod pod;
daisysp::Tube tube;

void AudioCallback(daisy::AudioHandle::InputBuffer in,
                   daisy::AudioHandle::OutputBuffer out,
                   size_t size)
{
    for (size_t i = 0; i < size; i++)
    {
        out[0][i] = tube.Process(in[0][i]);
        out[1][i] = out[0][i];  // Mono to stereo
    }
}

int main()
{
    pod.Init();
    tube.Init(pod.AudioSampleRate());
    tube.SetDrive(0.5f);
    
    pod.StartAudio(AudioCallback);
    while(1) {}
}

API Pattern

All modules follow the DaisySP API conventions:

namespace daisysp
{
class EffectName
{
public:
    // Initialize with sample rate
    void Init(float sample_rate);
    
    // Process single sample
    float Process(const float &in);
    
    // Parameter setters
    inline void SetParam(const float &value) { param_ = value; }
    
private:
    float sample_rate_;
    float param_;
};
}

Project Structure

DAFX_2_Daisy_lib/
├── src/                    # Library source code
│   ├── effects/           # Audio effects (tube, wahwah, etc.)
│   ├── filters/           # Filter modules (shelving, peak EQ)
│   ├── dynamics/          # Dynamics processors (noise gate)
│   ├── modulation/        # Modulation effects (vibrato, ring mod)
│   ├── spatial/           # Spatial processing (panning)
│   ├── analysis/          # Analysis tools (planned)
│   └── utility/           # Helper classes (planned)
├── tests/                 # Unit tests (Google Test)
├── examples/              # Usage examples
├── docs/                  # Reference documentation
├── plans/                 # Implementation planning docs
├── DAFX-MATLAB/          # Original MATLAB reference code
├── CMakeLists.txt        # Build configuration
├── CHECKPOINT.md         # Project status tracking
└── README.md             # This file

flowchart LR

  %% ===== Root =====
  A[DAFX_2_Daisy_lib/]:::root

  %% ===== Top-level groups =====
  subgraph TOP["Top Level"]
    direction TB
    SRC[src/]:::folderMain
    TESTS[tests/]:::folder
    EXAMPLES[examples/]:::folder
    DOCS[docs/]:::folder
    PLANS[plans/]:::folder
    MATLAB[DAFX-MATLAB/]:::folderMain
  end

  subgraph FILES["Project Files"]
    direction LR
    CMAKE[CMakeLists.txt]:::fileKey
    CHECKPOINT[CHECKPOINT.md]:::file
    README[README.md]:::fileKey
  end

  %% Root connections
  A --> TOP
  A --> FILES

  %% ===== src/ panel (rotated clockwise) =====
  subgraph SRC_PANEL["src/ - modules (Algorithm Categories)"]
    direction LR
    EFFECTS["effects/<br/>(tube, wahwah…)"]:::catAnalog
    FILTERS["filters/<br/>(shelving, peak EQ)"]:::catFilters
    DYNAMICS["dynamics/<br/>(noise gate)"]:::catDyn
    MODULATION["modulation/<br/>(vibrato, ring mod)"]:::catMod
    SPATIAL["spatial/<br/>(panning)"]:::catSpatial
    ANALYSIS["analysis/<br/>(planned)"]:::catAnalysis
    UTILITY["utility/<br/>(planned)"]:::moduleNeutral
  end

  %% Expand src/
  SRC --> SRC_PANEL

  %% ===== Styling =====
  classDef root fill:#2c3e50,color:#ffffff,stroke:#1a252f,stroke-width:2px

  %% Top-level project structure
  classDef folder fill:#3498db,color:#ffffff,stroke:#1f6fa5
  classDef folderMain fill:#2980b9,color:#ffffff,stroke:#1f6fa5,stroke-width:2px

  %% Algorithm Category palette (match DAFX diagram)
  classDef catFilters  fill:#3498db,color:#ffffff,stroke:#1f6fa5,stroke-width:2px
  classDef catMod      fill:#9b59b6,color:#ffffff,stroke:#6d3f86,stroke-width:2px
  classDef catDyn      fill:#e74c3c,color:#ffffff,stroke:#b03a2e,stroke-width:2px
  classDef catSpatial  fill:#1abc9c,color:#ffffff,stroke:#148f77,stroke-width:2px
  classDef catAnalysis fill:#95a5a6,color:#000000,stroke:#707b7c,stroke-width:2px
  classDef catAnalog   fill:#e67e22,color:#ffffff,stroke:#af601a,stroke-width:2px
  classDef moduleNeutral fill:#bdc3c7,color:#2c3e50,stroke:#95a5a6,stroke-width:2px

  %% Files
  classDef file fill:#ecf0f1,color:#2c3e50,stroke:#bdc3c7
  classDef fileKey fill:#fdf2e9,color:#6e2c00,stroke:#e59866,stroke-width:2px
Loading

Testing

Tests use Google Test framework (automatically fetched via CMake FetchContent):

cd build
ctest --output-on-failure

# Or run the test executable directly
./tests/dafx_tests

See tests/TEST_PATTERNS.md for testing guidelines.

Roadmap

Phase 1: Foundation (Complete ✅)

  • Tube Distortion
  • Low/High Shelving Filters
  • Peak/Parametric EQ
  • Vibrato
  • Ring Modulator
  • Stereo Panning
  • Noise Gate
  • Wah-Wah
  • Tone Stack

Phase 2: Enhancement (Complete ✅)

  • YIN Pitch Detection
  • Robotization
  • Whisperization
  • SOLA Time Stretch
  • FDN Reverb
  • Compressor/Expander
  • Universal Comb Filter
  • LP-IIR Comb Filter

Phase 3: Advanced (Complete ✅)

  • Spectral Filter
  • Phase Vocoder
  • Crosstalk Canceller

See plans/DAFX_DaisySP_Implementation_Plan.md for detailed roadmap.

Hardware Requirements

Designed for Daisy Seed (STM32H750, ARM Cortex-M7):

Parameter Value
CPU Clock 480 MHz
RAM 512KB internal + 64MB external
Audio 24-bit, up to 96 kHz
FPU Single and Double precision

Performance Targets

Effect Type Target CPU Target RAM
Simple Filter < 5% < 100 bytes
Complex Effect < 25% < 50 KB

References

Contributing

Contributions welcome! Please:

  1. Follow the DaisySP style guide (see docs/style_guide.pdf)
  2. Include unit tests for new effects
  3. Add documentation with DAFX chapter references
  4. Ensure all tests pass before submitting

License

MIT License — See LICENSE for details.

For project status and session history, see CHECKPOINT.md

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DAFX matlab port to DaisySP

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