294 lines
3.6 KiB
Markdown
294 lines
3.6 KiB
Markdown
# HubAudio SPI Control Architecture
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- Status: Draft
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- Date: 2026-08-01
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- Document Type: Architecture Specification
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# 1. Overview
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The HubAudio system separates the control communication layer from the audio
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signal layer.
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SPI is used exclusively for:
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- device configuration
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- initialization
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- status monitoring
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- firmware loading procedures
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- parameter management
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SPI is not used for real-time audio transport.
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The control architecture is based on independent SPI domains.
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CONTROL PLANE
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ESP32-S3
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System Controller
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SPI Control Bus
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+-----------+-----------+
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ADAU1467 Si4684
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Audio Processor Radio Receiver
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---
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# 2. ESP32-S3 Control Domain
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The ESP32-S3 is the system supervisor.
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Its responsibilities are:
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- system startup
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- peripheral initialization
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- configuration management
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- communication with external devices
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- firmware update coordination
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The ESP32-S3 owns the main control SPI interface.
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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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The control bus is independent from all audio data paths.
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---
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# 3. ADAU1467 SPI Domain
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The ADAU1467 contains its own SPI interface for external control.
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The ESP32-S3 uses this interface for:
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- DSP configuration
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- parameter updates
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- operational control
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- status reading
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The ADAU1467 also manages its external program memory.
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ADAU1467
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+----------------------+
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| SPI MASTER
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v
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25AA1024
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DSP Program Memory
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The ESP32-S3 does not directly access the EEPROM during normal operation.
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The ADAU1467 is responsible for loading its DSP configuration.
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---
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# 4. Si4684 SPI Domain
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The Si4684 is controlled by the ESP32-S3 through its SPI slave interface.
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The ESP32-S3 manages:
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- initialization sequence
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- command exchange
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- configuration
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- firmware loading procedure
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ESP32-S3
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SPI MASTER
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Si4684
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Internal Firmware Management
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Internal RAM
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The Si4684 remains responsible for its internal operational memory.
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---
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# 5. SPI Bus Isolation Principle
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The HubAudio architecture intentionally avoids a single shared SPI bus.
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The design uses:
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ESP32-S3
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+-------------+
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SPI-A SPI-B
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ADAU1467 Si4684
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Advantages:
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- no chip-select conflicts
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- independent timing
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- reduced electrical loading
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- easier firmware management
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- simpler debugging
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---
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# 6. Boot Sequence
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The expected startup sequence is:
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Power ON
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ESP32-S3 boot
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Initialize SPI buses
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Configure ADAU1467
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+--> ADAU loads DSP program from 25AA1024
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Configure Si4684
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+--> Firmware initialization
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Enable Audio Domain
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ADAU1467 starts audio processing
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---
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# 7. Separation Between Domains
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## Control Domain
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ESP32-S3
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SPI
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Peripheral configuration
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## Audio Domain
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Audio Sources
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I2S
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ADAU1467
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Audio Outputs
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The two domains interact only through configuration and status information.
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---
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# 8. Design Rules
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SPI signals require:
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- controlled routing
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- clean reference plane
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- appropriate termination where required
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- separation from high-speed clock signals
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Critical signals:
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- SCLK
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- MOSI
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- MISO
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- CS
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---
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# 9. Design Philosophy
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The ESP32-S3 is the system coordinator.
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The ADAU1467 is the audio processor.
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The Si4684 is a specialized audio peripheral.
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Each component controls its own functional domain while remaining part of the
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complete HubAudio system. |