# ADR-001:  Audio Processor as Audio Domain Master

- Status: Accepted
- Date: 2026-08-01
- Decision Type: Architecture

## Context

HubAudio is designed as a modular digital audio platform integrating several
audio sources and destinations:

- System Controller streaming subsystem
- Radio Receiver radio receiver
- Bluetooth RX/TX modules
- Digital audio converters
- Analog CODEC/DAC stages

The system requires a central component responsible for:

- digital audio routing
- DSP processing
- timing synchronization
- audio stream management

The  Audio Processor has been selected as the central audio processor.

## Decision

The  Audio Processor is the master component of the HubAudio Audio Domain.

The  Audio Processor is responsible for:

- DSP processing
- audio routing
- digital mixing
- signal processing
- audio clock generation
- synchronization of external audio peripherals

The  Audio Processor is considered the audio domain master.

The System Controller participates in the Audio Domain as a digital audio source. It does not act as the audio timing master or routing controller. Its role inside the audio domain is equivalent to other digital audio sources.
The System Controller has a dual role:

- audio source inside the Audio Domain
system supervisor inside the Control Domain

It operates as system supervisor and is responsible for:

- network connectivity
- user interface
- configuration management
- firmware update management
- system control

## Consequences

### Positive

- Single audio timing reference
- Deterministic audio routing
- Reduced clock synchronization complexity
- Easier debugging and expansion
- Clear separation between control domain and audio domain

### Negative

- External audio devices must support slave clock operation
- Clock distribution becomes a critical design element
- Peripheral selection must consider I2S synchronization requirements

## Rationale

The  Audio Processor is selected not only as a DSP processor but as the central
controller of the digital audio domain.

This decision defines the HubAudio architecture.