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