93 lines
1.7 KiB
Markdown
93 lines
1.7 KiB
Markdown
# ADR-002: SPI Control Architecture
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- Status: Accepted
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- Date: 2026-08-01
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- Decision Type: Hardware Architecture
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## Context
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HubAudio integrates multiple programmable devices requiring configuration,
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control and firmware management.
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The main devices involved are:
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- ESP32-S3 system controller
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- ADAU1467 audio processor
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- Si4684 radio receiver
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A clear separation between system control and internal device management is
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required.
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The SPI interface is used exclusively as a control interface and not as an
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audio transport interface.
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## Decision
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The SPI architecture is divided into independent domains.
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The ESP32-S3 operates as the master of the system control SPI bus.
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The ADAU1467 and Si4684 expose SPI slave interfaces for external configuration.
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Each device maintains its own internal SPI master domain for accessing local
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memories or peripherals.
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## Architecture
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System control bus:
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ESP32-S3
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SPI MASTER
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+---------+---------+
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ADAU1467 Si4684
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SPI SLAVE SPI SLAVE
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ADAU1467 local memory:
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ADAU1467
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SPI MASTER
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25AA1024
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DSP Configuration Memory
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Si4684 local memory:
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Si4684
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SPI MASTER
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Firmware Memory
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## Consequences
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### Positive
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- Clear ownership of every SPI bus
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- Reduced electrical loading
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- Independent firmware management
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- Easier debugging
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### Negative
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- Multiple SPI peripherals are required
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- Firmware coordination is required between domains
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## Rationale
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The ESP32-S3 supervises the system but does not replace the internal
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controllers of specialized devices.
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Each component remains responsible for its own functional domain. |