DSP MX

DSP Guitar MultiFX

An open-source modular real-time embedded DSP platform for guitar multi-effects, built around the Teensy 4.1.

The project combines real-time audio processing, embedded firmware, custom electronics, user-interface hardware, PCB design, and mechanical design into a complete standalone multi-effects platform.

Overview

DSP Guitar MultiFX was developed as an open and extensible platform for implementing real-time audio effects on embedded hardware.

The system uses a Teensy 4.1 with the SGTL5000-based Teensy Audio Board and a modular C++ firmware architecture designed to make additional effects easy to integrate.

Current effects include:

• Delay
• Reverb
• Chorus

The project includes the complete firmware alongside hardware design files, PCB resources, mechanical design, documentation, and bill of materials.

Key Features

• Teensy 4.1 ARM Cortex-M7 platform
• Real-time embedded audio processing
• Modular C++ DSP architecture
• Extensible IEffect interface for additional effects
• Delay, Reverb, and Chorus effects
• SGTL5000 audio interface
• OLED-based user interface
• Rotary encoder parameter control
• Dedicated effect footswitches
• PlatformIO + Arduino framework
• Custom PCB and hardware design
• Mechanical enclosure design
• Open-source hardware and firmware

Performance

Current experimental evaluation is performed at 44.1 kHz using 128-sample audio blocks.

CPU Utilization

These values were recorded for an earlier experimental firmware configuration. They have not been revalidated for the current routing and UI revision.

These measurements predate the optional chorus wet-filter routing and expanded UI. Repeat timing, CPU-load, and frequency-response measurements on that revision; see audio routing and controls.

Audio Measurement Record

See Experimental measurements for the measurement procedure, original oscilloscope captures, frequency-response data, delay timing and feedback ratios, and reverb/chorus test configurations.

The frequency-response sweep characterizes an earlier effects-off sketch with a shared 3.2 kHz pre-filter. It does not characterize the current unfiltered dry path. Harmonic, noise and latency estimates remain preliminary; their limitations and missing acquisition details are disclosed in the report.

System Architecture

The platform separates audio processing, DSP effects, system control, and user-interface functionality into independent modules.

Guitar Input
     │
     ▼
Analog / Audio Interface
     │
     ▼
SGTL5000 Codec
     │
     ▼
Teensy 4.1
     │
     ├── Audio Routing
     ├── DSP / Effects
     ├── Effect Manager
     ├── System Control
     └── User Interface
     │
     ▼
Audio Output

The firmware source is divided into:

firmware/src/
├── audio/
├── core/
├── dsp/
├── effects/
├── ui/
└── main.cpp

This organization keeps individual effects separated from audio routing and interface logic.

Hardware

The platform is built around:

• Teensy 4.1
• Teensy Audio Board / SGTL5000
• Custom interface PCB
• 128×64 OLED display
• Rotary encoder
• Dedicated effect footswitches
• Audio input/output connections
• Custom enclosure

PCB

Top	Bottom

Schematic

Hardware design resources are available in the Hardware directory.

Firmware

The firmware is implemented in C++ using the Arduino framework for Teensy and built using PlatformIO.

Current PlatformIO dependencies include:

• U8g2
• CriticalTaskScheduler

The repository is configured for:

platform = teensy
board = teensy41
framework = arduino

Adding a New Effect

The DSP architecture is designed to make effects modular.

To implement a new effect:

1. Create the new effect implementation inside firmware/src/effects/.
2. Implement the project's effect interface.
3. Define the effect parameters and processing logic.
4. Register the effect with the effect-management system.
5. Connect its parameters to the user interface as required.

This allows new algorithms such as distortion, tremolo, or additional modulation effects to be integrated without redesigning the complete audio system.

Repository Structure

DSP-Guitar-MultiFX/
├── BOM/          # Bill of materials
├── Docs/         # Technical documentation
├── Hardware/     # PCB and hardware design
├── Images/       # Project images and renders
├── Mechanical/   # Mechanical / enclosure design
├── firmware/     # Teensy firmware
└── README.md

Getting Started

Clone the repository:

git clone https://github.com/MahmoudBasio/DSP-Guitar-MultiFX.git
cd DSP-Guitar-MultiFX/firmware

Open the firmware directory using VS Code + PlatformIO.

Build the project:

pio run

Upload to the Teensy 4.1:

pio run --target upload

Research

This platform is also being developed and experimentally evaluated as part of research into modular, low-cost, open-source real-time embedded DSP systems.

Experimental results, architecture details, resource utilization, latency, and audio-performance measurements are being documented as part of the associated research work.

Publication information and DOI will be added here when available.

Citation

If you use this project in academic or research work, please cite the repository using the citation information provided in CITATION.cff.

Publication citation information will be added following publication of the associated research article.

License

This project is released under the MIT License. See LICENSE for details.

Author

Mahmoud Basiony

Robotics • Embedded Systems • Real-Time DSP

• GitHub: @MahmoudBasio
• LinkedIn: linkedin.com/in/basio
• ORCID: https://orcid.org/0009-0007-1747-1609

Tamer Mohamed

Robotics • Mechanical Designer • Real-Time DSP

• GitHub: @Temo-MO
• LinkedIn: https://www.linkedin.com/in/tamer-mohamed-16123a294/

Project Status

Active development.

Planned work includes additional DSP effects, expanded experimental characterization, audio-quality measurements, and further hardware refinement.