42dB DSP Engine

Real-time audio DSP engine for the 42dB audio platform, built around STM32-based signal processing with BLE control through a dedicated bridge layer.

This repository contains the core embedded DSP layer of the 42dB platform. It receives audio over I2S, applies real-time processing such as EQ, loudness control, and dynamics, and forwards the processed stream to the output stage. Control and state updates reach the DSP engine through the companion control stack and the ChaoticVolt-BLE-I2S-Bridge repository.

At a glance

• Role: core DSP engine for the 42dB audio platform
• Primary targets: STM32H753 and STM32F446 platform revisions
• Audio path: transport/front-end layer -> I2S -> STM32 DSP -> DAC/output stage
• Control path: companion app -> BLE GATT -> bridge layer -> UART/control link -> STM32
• Status: active platform component

Ecosystem context

This project is part of a small multi-repository product ecosystem around the 42dB platform.

Closely related repositories include:

• ChaoticVolt-42dB-Companion-App — iPhone and Apple Watch control layer
• ChaoticVolt-BLE-I2S-Bridge — bridge layer for control translation and transport-facing integration

Together, these repositories form the control, transport, and signal-processing spine of the 42dB system.

Architecture

The current 42dB platform separates the control path, transport-facing bridge layer, DSP engine, and downstream output stage.

Current integration path

┌───────────────┐   Bluetooth Audio   ┌────────────────────────────┐   I2S  ┌──────────────────────────────┐   I2S  ┌──────────────┐
│ Phone / Tablet│────────────────────>│Transport / Front-End Layer │───────>│ ChaoticVolt-42dB-DSP-Engine  │───────>│ DAC / Output │
└───────────────┘                     └────────────────────────────┘        └──────────────────────────────┘        └──────────────┘
        │
        │ BLE GATT control
        ▼
┌────────────────────────────┐   BLE GATT  ┌────────────────────────────┐   UART / control link   ┌──────────────────────────────┐
│ ChaoticVolt-42dB-Companion │────────────>│ ChaoticVolt-BLE-I2S-Bridge │────────────────────────>│ ChaoticVolt-42dB-DSP-Engine  │
│ -App                       │             │                            │                         │                              │
└────────────────────────────┘             └────────────────────────────┘                         └──────────────────────────────┘

The transport/front-end layer may currently be implemented with an ESP32-based path and may later move toward BM83-based audio ingress or other front-end revisions. The public architecture stays the same: transport feeds the DSP engine, while control reaches it through the companion app and bridge layer.

For a more detailed architectural breakdown, see docs/architecture.md and docs/control-interface.md.

Overview

The DSP engine sits between the incoming digital audio path and the final output stage. Audio arrives over I2S, is processed in real time on the STM32-based DSP layer, and is then forwarded toward the DAC and downstream playback chain.

Processing currently includes building blocks such as:

• EQ
• loudness control
• normalization and dynamics-oriented processing
• additional platform-specific DSP stages as the project evolves

Control commands are received through the bridge layer and applied inside the DSP engine, which also maintains DSP-side state for synchronization back toward the user-facing control path.

This repository is one part of a broader 42dB platform. It is not just a board-specific firmware exercise, but the main signal-processing layer in a system that also includes app-side control and dedicated transport/control bridge components.

Hardware targets

The project currently targets:

• STM32H753ZI on Nucleo-144 during development and prototyping
• STM32F446VET6 for the custom-board-oriented target path

Associated platform components may include:

• bridge-layer hardware such as ESP32-based implementations
• external DACs such as PCM5102A
• Bluetooth audio front-end components such as BM83 or equivalent transports

These parts are implementation details of the current platform architecture, not strict long-term requirements for every future revision.

Related projects

• ChaoticVolt-42dB-Companion-App — app-side control surface for the 42dB platform
• ChaoticVolt-BLE-I2S-Bridge — bridge layer between BLE-facing control, transport responsibilities, and the DSP engine
• ChaoticVolt Labs — broader public repository context for the platform and adjacent projects

Build and status

• Version: 0.5.0
• Build: 59
• Date: 2026-02-18

Documentation

See the docs/ directory for the evolving technical documentation set:

• docs/overview.md — product and repository summary
• docs/architecture.md — system layout and component relationships
• docs/signal-flow.md — audio path and DSP processing flow
• docs/hardware-targets.md — target MCU platforms and hardware notes
• docs/control-interface.md — companion-app to DSP control path
• docs/development-notes.md — prototype notes, constraints, and evolving implementation decisions
• And many more.

Notes

This repository reflects an actively evolving product platform. Some implementation choices are influenced by prototype hardware availability and may shift as the hardware stack matures.

Prototype hardware and board-specific details are documented here because they matter to development, but the main focus of the project is the 42dB DSP engine as a reusable platform component rather than a single-board demo.