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old_docs/HUBAudio_Bus_and_Pin_Assignment.md

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+# HubAudio
+# Bus Architecture and Preliminary Pin Assignment
+
+**Document:** Hardware Interface Definition  
+**Revision:** 0.1  
+**Status:** Preliminary Design  
+**Controller:** ESP32-S3
+
+
+---
+
+# 1. Purpose
+
+This document defines the preliminary hardware interfaces between the ESP32-S3 system controller and all HubAudio modules.
+
+The purpose is to establish:
+
+- bus ownership
+- GPIO allocation
+- peripheral assignment
+- boot-safe pins
+- expansion possibilities
+
+
+This document must be reviewed before PCB routing.
+
+
+---
+
+# 2. Design Rules
+
+
+The following rules apply:
+
+
+## Rule 1
+
+The ESP32-S3 controls configuration only.
+
+
+Audio data does not pass through the MCU.
+
+
+---
+
+## Rule 2
+
+All audio sources connect directly to ADAU1467.
+
+
+
+SOURCE
+
+|
+
+I2S
+
+|
+
+ADAU1467
+
+
+
+---
+
+## Rule 3
+
+Every external module must be identifiable.
+
+
+Identification:
+
+
+24AA025E48T-I/OT
+
+
+
+---
+
+# 3. ESP32-S3 Peripheral Allocation
+
+
+## 3.1 Overview
+
+
+| Function | Interface |
+|-|-|
+| Radio control | SPI |
+| DSP control | I2C |
+| Module EEPROM | I2C |
+| Bluetooth control | UART |
+| Debug | USB/JTAG |
+| Expansion | Reserved GPIO |
+
+
+---
+
+# 4. Proposed GPIO Map
+
+
+## 4.1 I2C Bus
+
+
+Shared bus:
+
+
+| Signal | ESP32-S3 GPIO | Devices |
+|-|-|-|
+| SDA | GPIO8 | EEPROM, ADAU1467 |
+| SCL | GPIO9 | EEPROM, ADAU1467 |
+
+
+Notes:
+
+- keep traces short
+- external pull-ups required
+- address conflicts must be checked
+
+
+---
+
+# 4.2 SPI Bus
+
+
+Used for radio and memories.
+
+
+| Signal | ESP32-S3 GPIO | Function |
+|-|-|-|
+| SCLK | GPIO12 | SPI Clock |
+| MOSI | GPIO11 | SPI Data |
+| MISO | GPIO13 | SPI Data |
+| CS_RADIO | GPIO10 | Si4684 |
+| CS_FLASH | GPIO14 | External memories |
+
+
+---
+
+# 4.3 UART Bus
+
+
+Bluetooth modules:
+
+
+## BT RX
+
+
+| Signal | GPIO |
+|-|-|
+| TX ESP32 | GPIO17 |
+| RX ESP32 | GPIO18 |
+
+
+## BT1035 TX
+
+
+Second UART:
+
+
+| Signal | GPIO |
+|-|-|
+| TX ESP32 | GPIO43 |
+| RX ESP32 | GPIO44 |
+
+
+Notes:
+
+ESP32-S3 provides multiple UART peripherals.
+
+
+---
+
+# 4.4 Module Control GPIO
+
+
+| Signal | GPIO | Function |
+|-|-|-|
+| RADIO_RESET | GPIO4 | Si4684 reset |
+| DSP_RESET | GPIO5 | ADAU1467 reset |
+| BT_RX_RESET | GPIO6 | BT receiver reset |
+| BT_TX_RESET | GPIO7 | BT1035 reset |
+
+
+---
+
+# 5. Si4684 Interface
+
+
+## Control
+
+
+SPI:
+
+
+
+ESP32-S3
+
+SCLK
+|
+Si4684 CLK
+
+MOSI
+|
+Si4684 SDIO
+
+CS
+|
+Si4684 CS
+
+
+
+Control:
+
+
+
+GPIO4
+
+|
+
+RESET
+
+
+
+Interrupt:
+
+
+
+Si4684 IRQ
+
+|
+
+ESP32 GPIO
+
+
+
+---
+
+# 6. ADAU1467 Interface
+
+
+## Control Interface
+
+
+Preferred:
+
+
+I2C
+
+
+
+ESP32-S3
+
+SDA
+
+SCL
+
+|
+
+ADAU1467
+
+
+
+Used for:
+
+
+- volume
+- routing
+- DSP parameters
+
+
+---
+
+# 7. Bluetooth TX Interface
+
+
+Device:
+
+FSC-BT1035
+
+
+## Control
+
+
+UART:
+
+
+
+ESP32-S3
+
+TX
+
+|
+
+BT1035 RX
+
+ESP32-S3
+
+RX
+
+|
+
+BT1035 TX
+
+
+
+---
+
+## Audio
+
+
+I2S:
+
+
+
+ADAU1467
+
+  |
+
+  |
+
+BT1035
+
+BCLK
+
+LRCLK
+
+DATA
+
+
+
+The clock direction must be verified.
+
+
+Preferred:
+
+
+ADAU1467 master.
+
+
+---
+
+# 8. Bluetooth RX Interface
+
+
+Device:
+
+FSC-BT1026 or equivalent.
+
+
+## Control
+
+
+UART:
+
+
+
+ESP32-S3
+
+|
+
+BT RX Module
+
+
+
+---
+
+## Audio
+
+
+
+BT RX
+
+|
+
+I2S OUT
+
+|
+
+ADAU1467 INPUT
+
+
+
+---
+
+# 9. I2S Architecture
+
+
+## Important Design Decision
+
+
+Multiple I2S sources are not connected together.
+
+
+Wrong:
+
+
+
+Si4684
+|
+|
+BT RX
+|
++------ I2S ------ ADAU1467
+
+
+
+Correct:
+
+
+
+Si4684
+
+I2S Port 0
+
+    |
+
+    |
+
+ADAU1467
+
+BT RX
+
+I2S Port 1
+
+    |
+
+    |
+
+ADAU1467
+
+
+
+The ADAU1467 internal serial ports perform routing.
+
+
+---
+
+# 10. Proposed ADAU1467 Serial Port Allocation
+
+
+| DSP Port | Device | Direction |
+|-|-|-|
+| Serial Input 0 | Si4684 | RX |
+| Serial Input 1 | BT RX | RX |
+| Serial Output 0 | DAC | TX |
+| Serial Output 1 | BT1035 | TX |
+
+
+---
+
+# 11. EEPROM Bus
+
+
+All modules include:
+
+
+
+24AA025E48T
+
+
+
+Example:
+
+
+| Module | Address |
+|-|-|
+| Main Board | 0x50 |
+| Radio | 0x51 |
+| Bluetooth | 0x52 |
+| DSP | 0x53 |
+
+
+Address selection must be verified.
+
+
+---
+
+# 12. Reserved Expansion Interface
+
+
+Future modules:
+
+
+Possible:
+
+- external DAC
+- amplifier module
+- display
+- sensors
+- remote control
+
+
+Reserved:
+
+
+SPI
+
+I2C
+
+UART
+
+I2S
+
+GPIO
+
+Power
+
+
+
+---
+
+# 13. Boot Safety Review
+
+
+ESP32-S3 boot pins must be checked.
+
+
+Before PCB release:
+
+
+Verify:
+
+- GPIO assignment
+- strapping pins
+- pull-up/pull-down resistors
+
+
+No external device must force an incorrect boot state.
+
+
+---
+
+# 14. Recommended Connector Between Modules
+
+
+For removable modules:
+
+
+Example:
+
+
+
+MODULE HEADER
+
+1 3.3V
+2 GND
+3 SDA
+4 SCL
+5 UART TX
+6 UART RX
+7 RESET
+8 IRQ
+9 I2S BCLK
+10 I2S LRCLK
+11 I2S DATA
+12 RESERVED
+
+
+
+---
+
+# 15. Final Review Before Schematic
+
+
+Before drawing schematic:
+
+
+Check:
+
+
+[ ] ESP32-S3 GPIO availability
+
+[ ] Boot strap conflicts
+
+[ ] I2S clock ownership
+
+[ ] Module power consumption
+
+[ ] RF placement
+
+[ ] EEPROM addressing
+
+[ ] Firmware update paths
+
+
+---
+
+# END