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-[📋 Setup Guide](Docs/SETUP.md) | [📋 Commands](Docs/commands.md) | [🔧 Local.h Reference](Docs/Local.md) | [🔬 Sensor Reference](Docs/Sensors.md) | [🔩 Bill of Materials](Docs/BOM.md)
-# SmartFuseBox ⚡
+# SmartFuseBox
 
-A modular, Arduino-powered **12V power distribution and control system** designed for boats and other off-grid applications.  
-SmartFuseBox combines fused relays, quick-connect aviation plugs, sensor monitoring, WiFi/BLE/MQTT connectivity, and Arduino-based control into a single 3D-printed enclosure — with a built-in security twist.
+**SmartFuseBox** is an Arduino-based 12V power distribution and control system for marine and off-grid applications. It provides configurable fused relay switching, multi-protocol sensor telemetry, WiFi/BLE/MQTT connectivity, and a companion touchscreen control panel — all managed through a unified serial command protocol and EEPROM-persisted configuration.
+
+> Current firmware version: **0.9.0** — see [`FirmwareVersion.h`](SmartFuseBox/FirmwareVersion.h).
 
 ---
 
-## 📖 Backstory
+## Table of Contents
+
+- [Overview](#overview)
+- [Key Features](#key-features)
+- [Architecture](#architecture)
+- [Board Support](#board-support)
+- [Installation](#installation)
+- [Configuration](#configuration)
+- [Usage](#usage)
+- [Subsystem Reference](#subsystem-reference)
+- [Limitations and Known Issues](#limitations-and-known-issues)
+- [Documentation](#documentation)
+- [License](#license)
+
+---
 
-I bought a mid-80s boat and wanted to give it a **modern electrical upgrade**.  
-The original wiring was dated, messy, and lacked any real security. Since the boat is kept in a marina, theft was also a concern.  
+## Overview
 
-SmartFuseBox was born out of the need for:
-- **Reliable 12V power distribution** for navigation lights, bilge pumps, and other onboard systems.  
-- **Quick-connect modularity** so I can easily add/remove systems with aviation connectors.  
-- **Integrated monitoring** via Arduino sensors (temperature, humidity, light, etc.).  
-- **Basic security** through a “poor man’s immobiliser” — the control unit must return a valid 12V feed before the system powers up.  
+SmartFuseBox is a single-unit firmware target running on an Arduino Uno R4 WiFi or ESP32 NodeMCU-32. The Nextion touchscreen display is driven directly by the SFB controller over a dedicated hardware serial port (`Serial2` for GPS; display connected via `NextionControl`).
+
+The firmware entry point is `SmartFuseBoxApp`, which owns all subsystem instances and wires them together at startup. Host and debug communication uses a text-based framed serial protocol:
+
+```
+<CMD>:<key>=<value>;<key>=<value>\n
+```
+
+Commands are grouped by prefix (`F`, `C`, `R`, `H`, `W`, `S`, `M`, `N`, `E`, `T`) and are available over serial, USB, and — where applicable — the HTTP REST API. See [Docs/Commands.md](Docs/Commands.md) for the full reference.
 
 ---
 
-## 🛠 Features
+## Key Features
+
+### Relay Control
+- Up to **8 independently configurable relay channels**, pin-assigned at runtime via configuration.
+- **Linked relays** — any relay can be configured to mirror the state of another.
+- **Default-on state** — individual relays can be initialised to active at boot.
+- **Pulse mode** — relay activates for a configurable duration (seconds) then turns off automatically.
+- **Named relays** — short name (5 chars) and long name (20 chars) stored in EEPROM for display use.
+- **Action types** — relays can be designated as `Default`, `Horn` (COLREGS sound signal output), or `NightRelay` (automatic day/night switching driven by the LDR sensor).
+- **Relay status bitmask** broadcast via `MessageBus` on every state change.
 
-### Power & Control
-- **8 fused relays** for distributing 12V power safely.
-- **Aviation connectors** for quick, reliable connections to onboard systems.
-- **Linked relays** — configure pairs that mirror each other's state.
-- **Default relay states** — individual relays can be set to default-on at boot.
-- **Immobiliser-style security** — the control unit must return a valid 12V feed to enable the system.
-- **3D-printed enclosure** for a compact, customizable housing.
+### Sensor Pipeline
 
-### Sensors
-- **DHT11** — temperature and humidity monitoring with failure detection.
-- **Water level** — analog sensor with 15-reading rolling average and corrosion-reduction active pin control.
-- **Light (LDR)** — day/night detection.
-- **GPS (GY-GPS6MV2)** — location, speed, altitude, heading, cumulative distance, and automatic UTC time sync.
-- **System diagnostics** — free memory, CPU usage, WiFi/BT state, SD log size, uptime, and warning count.
-- **Extensible** — add custom local or remote sensors with minimal boilerplate (see [Docs/Sensors.md](Docs/Sensors.md)).
+All sensors inherit from `BaseSensor` and are registered with `SensorController`. The `RemoteSensor` class provides an extensibility point for sensors on external devices that push readings via serial.
+
+| Sensor | Class | Poll Interval | Notes |
+|---|---|---|---|
+| **DHT11** | `Dht11SensorHandler` | 2 500 ms | Temperature (°C) and relative humidity (%). Raises `TemperatureSensorFailure` warning on read error; clears automatically on recovery. |
+| **Light (LDR)** | `LightSensorHandler` | 30 000 ms | Rolling average over 10 readings. 3-reading debounce before day/night state change. Configurable ADC threshold (default 512). Drives a `NightRelay` automatically. |
+| **Water Level** | `WaterSensorHandler` | Configurable | 15-reading rolling average. Active-pin corrosion-reduction control (power applied only during measurement). |
+| **GPS** | `GpsSensorHandler` | Continuous | GY-GPS6MV2 (NMEA). Reports latitude, longitude, altitude, speed (km/h), course, cumulative distance. Provides UTC time for automatic RTC synchronisation. Raises `GpsFailure` warning if no valid fix for 30 seconds. |
+| **System Diagnostics** | `SystemSensorHandler` | Configurable | Free heap memory, CPU usage percentage, WiFi/BT enabled state, SD log file size (bytes), system uptime (`d HH:MM:SS`), active warning count. |
+
+Sensors expose data over Serial, WiFi REST, BLE, and MQTT. Custom local or remote sensors can be added with minimal boilerplate; see [Docs/Sensors.md](Docs/Sensors.md).
 
 ### Connectivity
-- **WiFi** (AP and Client mode) with a full HTTP REST API for relay control, sensor data, configuration, sound, and warnings.
-- **Bluetooth BLE** — relay control, sensor streaming, and system metrics via BLE characteristics.
-- **MQTT** with **Home Assistant auto-discovery** — sensors and relays appear as HA entities automatically.
-- **Serial command protocol** for integration with the companion Boat Control Panel (Arduino Mega + Nextion display).
-
-### Diagnostics & Logging
-- **SD card logging** — persistent system logs with configurable SPI speed.
-- **Warning system** — 32-bit bitmask of typed warnings propagated between both controllers.
-- **RTC support** — DS1302 real-time clock with automatic GPS UTC time synchronisation.
-- **CPU usage and free memory monitoring** available via serial, WiFi, and MQTT.
-
-### Boat Control Panel
-- **Nextion touchscreen** display for relay switching, sensor readout, and system configuration.
-- **COLREGS sound signals** (H0–H12) via a reserved relay-driven horn.
-- **Config synchronisation** — BCP and SFB automatically stay in sync over the serial link.
+
+#### WiFi
+- Operates in **Access Point** or **Client** mode, selectable via `C12`.
+- Implements **persistent HTTP connections** to reduce TCP handshake overhead on resource-constrained hardware.
+- Supports up to **8 concurrent clients** (`MaxConcurrentClients`).
+- Automatic reconnection with exponential backoff in Client mode.
+- RSSI monitoring — raises `WeakWifiSignal` warning when signal falls below −70 dBm.
+- Full REST API across 9 route groups:
+
+| Route | Handler | Purpose |
+|---|---|---|
+| `/api/relay` | `RelayNetworkHandler` | Relay state read/write |
+| `/api/sensor` | `SensorNetworkHandler` | Sensor telemetry |
+| `/api/sound` | `SoundNetworkHandler` | COLREGS horn signals |
+| `/api/system` | `SystemNetworkHandler` | System status, heartbeat, OTA |
+| `/api/config` | `ConfigNetworkHandler` | Configuration read/write |
+| `/api/warning` | `WarningNetworkHandler` | Warning bitmask access |
+| `/api/timer` | `SchedulerNetworkHandler` | Scheduled event read |
+| `/api/externalsensor` | `ExternalSensorNetworkHandler` | Remote sensor config |
+| `/` | `WebIndexNetworkHandler` | Index page |
+
+Uses a platform-abstraction interface (`IWifiRadio`) to isolate board-specific WiFi drivers from application logic.
+
+#### Bluetooth BLE
+- Available on boards with `BLUETOOTH_SUPPORT` defined.
+- Exposes three GATT services via `BluetoothManager`:
+  - `BluetoothSystemService` — system diagnostics characteristics.
+  - `BluetoothSensorService` — sensor telemetry characteristics with notifications.
+  - `BluetoothRelayService` — relay state read and write characteristics.
+- Single-client model. Advertising restarts automatically after disconnect.
+- No pairing or bonding. Device advertises as **"Smart Fuse Box"**.
+- Uses `IBluetoothRadio` interface — higher-level code operates exclusively through the interface pointer, with runtime null-checks replacing compile-time guards.
+- **Arduino Uno R4 WiFi constraint:** WiFi and BLE share the RF path on the ANNA-B112/ESP32-S3 modules; `BLUETOOTH_SUPPORT` and `WIFI_SUPPORT` are mutually exclusive on this board. Enforced by a compile-time `#error`. On ESP32, both can operate simultaneously.
+
+#### MQTT
+- Custom **MQTT 3.1.1** client implementation (`MQTTClient`) — no third-party MQTT library dependency.
+- **Home Assistant auto-discovery** — all sensors and relays register as HA entities on connect.
+- Configurable broker address (64 chars), credentials (32 chars each), device ID, discovery prefix, port (default 1883), and keepalive interval (default 60 s).
+- Requires `WIFI_SUPPORT`. Guarded by `#if defined(WIFI_SUPPORT)` in `BoardConfig.h`.
+
+### Warning System
+
+A **32-bit bitmask** tracks up to 32 independent typed conditions within `WarningManager`.
+
+- **Sensor failure aggregation**: any sensor warning (bits 21–31) automatically raises `SensorFailure` (bit 20). `SensorFailure` clears only when all sensor warnings are cleared.
+- Warning state changes are broadcast on the `MessageBus` via `WarningChanged`.
+- Full warning type reference: [Docs/Warnings.md](Docs/Warnings.md).
+
+### Scheduler
+
+Event-driven relay automation engine with EEPROM-persisted configuration.
+
+- Up to **20 events** (6 on boards with ≤ 1 KB EEPROM) stored in `SchedulerSettings`.
+- Each event specifies an independent **trigger**, **condition guard**, and **action**.
+
+| Dimension | Supported Values |
+|---|---|
+| **Triggers** | `TimeOfDay`, `Sunrise`, `Sunset`, `Interval`, `DayOfWeek`, `Date` |
+| **Conditions** | `TimeWindow`, `DayOfWeek`, `IsDark`, `IsDaylight`, `RelayIsOn`, `RelayIsOff` |
+| **Actions** | `RelayOn`, `RelayOff`, `RelayToggle`, `RelayPulse`, `AllRelaysOn`, `AllRelaysOff`, `SetPinHigh`, `SetPinLow` |
+
+Sunrise and sunset triggers are computed in real time from GPS coordinates by `SunCalculator`. The `IsDark` / `IsDaylight` conditions fall back to the LDR sensor when GPS is unavailable.
+
+### Message Bus
+
+`MessageBus` provides a **lightweight publish/subscribe event system** for internal component decoupling. No dynamic allocation occurs at publish time — subscriber lists use function-local statics.
+
+Key events: `WarningChanged`, `RelayStatusChanged`, `TemperatureUpdated`, `HumidityUpdated`, `LightSensorUpdated`, `WaterLevelUpdated`, `GpsLocationUpdated`, `GpsAltitudeUpdated`, `GpsSpeedUpdated`, `WifiConnectionStateChanged`, `WifiSignalStrengthChanged`, `SystemMetricsUpdated`. Full reference: [Docs/MessageBus.md](Docs/MessageBus.md).
+
+### Over-the-Air Updates (OTA)
+
+- Available on **ESP32 + `WIFI_SUPPORT` + `OTA_AUTO_UPDATE`** only.
+- Polls the GitHub Releases API (`SmartFuseBox/SmartFuseBox`) every **24 hours**.
+- Downloads asset `SmartFuseBox-esp32-v{major}.{minor}.{patch}.{build}.bin` with SHA-256 checksum verification.
+- TLS connections use pinned root CA certificates (Sectigo E46 for `api.github.com`; ISRG Root X1 for `assets.githubusercontent.com`).
+- **Auto-apply is disabled by default.** Enable via `F12:apply=1` or the `OtaFlagAutoApply` bit in `SystemHeader::reserved[0]`.
+- OTA state (`idle`, `checking`, `available`, `downloading`, `rebooting`, `failed`, `uptodate`) is queryable at any time via `F13`.
+
+### Diagnostics and Logging
+
+- **SD card logging** via `SdCardLogger` / `MicroSdDriver`. Configurable SPI pins (`C4`). Raises `SpiPinConfigError`, `SdCardMissing`, `SdCardError`, or `SdCardLowSpace` warnings as appropriate.
+- Optional **SD card config loader** (`CARD_CONFIG_LOADER`) — reads `config.txt` at boot to override EEPROM settings without reflashing.
+- **DS1302 RTC** (`RtcDS1302Driver`) with configurable pins (`C18`). Automatically synchronised from GPS UTC time on each valid GPS fix.
+- **CPU usage monitoring** via `SystemCpuMonitor`. Available over serial, WiFi, and MQTT.
+- **Boot counter** and **crash counter** tracked in `SystemHeader` with magic number validation (`0x53464201`).
+- **RGB LED warning indicator** (HW479) driven on configurable pins (`C8`).
+
+### Nextion Display
+
+- `NavigationController` manages an ordered list of active pages, rebuilt dynamically when the location type changes — no reboot required.
+- Maritime-specific pages (buoys, cardinal markers, flags, VHF radio, COLREGS sound signals) are included in the page list only when `LocationType` is `Power`, `Sail`, `Fishing`, or `Yacht`.
+- Pages included: Splash, Home, Relay, Relay Settings, Environment, System, Warning, Settings, About, Buoys, Cardinal Markers, Flags, Moon Phase, Sound (Fog / Maneuvering / Overtaking / Emergency / Other / Signals), VHF (Channels / Distress / Radio).
+
+### Security
+
+- **API key and HMAC key** fields (32 chars each) are reserved in the `Config` struct for future HTTP authentication.
 
 ---
 
-## 🧩 Board Support
+## Architecture
 
-| Board | WiFi | BLE | MQTT | Notes |
-|---|---|---|---|---|
-| **Arduino Uno R4 WiFi** | ✅ | ✅ | ✅ | WiFi and BLE are mutually exclusive on this board |
-| **Arduino Uno R4 Minima** | ❌ | ❌ | ❌ | Serial and sensor support only |
-| **ESP32 NodeMCU-32** | ✅ | ✅ | ✅ | Full feature support |
+### Repository Structure
 
-Board selection is controlled by a single `#define` in `Local.h`.
+```
+SmartFuseBox/    Firmware source (relays, sensors, WiFi, BLE, MQTT, OTA, SD, Nextion display)
+Docs/            Reference documentation
+TestData/        Serial command test scripts
+```
+
+### Subsystem Dependency Graph
+
+```
+SmartFuseBoxApp
+├── MessageBus                  Pub/sub event bus (no dynamic allocation)
+├── RelayController             Relay switching, linking, pulse, action types
+├── SoundController             COLREGS signal sequencer -> horn relay
+├── SensorController            Sensor pipeline (local + remote)
+│   ├── Dht11SensorHandler
+│   ├── LightSensorHandler
+│   ├── WaterSensorHandler
+│   ├── GpsSensorHandler
+│   ├── SystemSensorHandler
+│   └── RemoteSensor (xN)
+├── ConfigController            EEPROM config lifecycle
+├── WarningManager              32-bit bitmask, sensor failure aggregation
+├── ScheduleController          Event engine: trigger -> condition -> action
+├── WifiController              WiFi lifecycle, HTTP REST API
+│   └── WifiServer              Connection state machine, request routing
+├── BluetoothController         BLE lifecycle (BLUETOOTH_SUPPORT)
+│   └── BluetoothManager
+│       ├── BluetoothSystemService
+│       ├── BluetoothSensorService
+│       └── BluetoothRelayService
+├── MQTTController              MQTT 3.1.1 client, HA auto-discovery (MQTT_SUPPORT)
+├── SdCardLogger                SD card log writer (SD_CARD_SUPPORT)
+├── RtcDS1302Driver             DS1302 real-time clock
+├── OtaManager                  GitHub OTA (OTA_AUTO_UPDATE + ESP32 + WIFI_SUPPORT)
+├── BroadcastManager            Centralised serial broadcast to computer/debug port
+├── NavigationController        Nextion page navigation (NEXTION_DISPLAY_DEVICE)
+└── SerialCommandManager        Framed serial command dispatch (USB/debug)
+```
+
+### Interface Abstraction Pattern
+
+WiFi and Bluetooth subsystems are each accessed through a platform-agnostic interface (`IWifiRadio`, `IBluetoothRadio`). Board-specific drivers (`R4WifiRadio`, `Esp32WifiRadio`, `BluetoothController`) are constructed only inside `SmartFuseBoxApp` under the appropriate `#if defined(...)` guard. All higher-level code operates through interface pointers with runtime null-checks, minimising preprocessor usage and enabling straightforward test doubles.
+
+### Configuration Persistence
+
+The `Config` struct is a versioned, packed POD serialised to EEPROM. The current layout version is **6** (`ConfigVersion6`). The `SystemHeader` (32 bytes) precedes the config payload and contains a magic number (`0x53464201`), boot count, crash counter, reset reason, OTA flags, and a 16-bit checksum. A config version mismatch triggers migration logic in `ConfigManager` and raises `DefaultConfigurationFuseBox`.
 
 ---
 
-## 🔌 System Architecture
+## Board Support
 
-### Physical Units
+| Board | WiFi | BLE | MQTT | OTA | Notes |
+|---|---|---|---|---|---|
+| **Arduino Uno R4 WiFi** | Yes | Yes | Yes | No | WiFi and BLE are mutually exclusive (shared RF path) |
+| **Arduino Uno R4 Minima** | No | No | No | No | Serial and sensor support only |
+| **ESP32 NodeMCU-32** | Yes | Yes | Yes | Yes | Full feature support; WiFi and BLE simultaneous |
 
-Two hardware units communicate over a 7-wire serial harness:
+Board selection is controlled by a single `#define` in `Local.h` using the trailing-underscore convention. `BoardConfig.h` derives all capability flags, EEPROM limits, and enforces incompatible feature combinations at compile time.
 
-| Unit | Hardware | Role |
-|---|---|---|
-| **Smart Fuse Box (SFB)** | Arduino Uno R4 / ESP32 | Relay control, sensor handling, WiFi, BLE, MQTT, SD logging |
-| **Boat Control Panel (BCP)** | Arduino Mega + Nextion | User interface, immobiliser logic, time sync, config management |
+---
+
+## Installation
+
+### Prerequisites
 
-The 7-wire harness carries: 12V in, 12V out (immobiliser return), GND, TX (link), RX (link), TX (GPS), RX (GPS).
+| Requirement | Details |
+|---|---|
+| **Arduino IDE** | 1.8.19 or Arduino IDE 2.x |
+| **Git for Windows** | Standard installation |
+| **Windows 10 / 11** | No special configuration required |
 
-### Software
+### Required Libraries (Arduino Library Manager)
 
-The firmware is split between two projects that share a common `Shared/` library via symlinks:
+| Library | Source |
+|---|---|
+| `SerialCommandManager` | Si Carter |
+| `DHT sensor library` | Adafruit |
+| `QMC5883LCompass` | Arduino Library Manager |
+| `NextionControl` | Custom — copy `NextionControl/` folder to Arduino `libraries/` directory |
 
+### Steps
+
+1. Clone the repository:
+
+   ```
+   git clone https://github.com/SmartFuseBox/SmartFuseBox
+   ```
+
+2. Install all required libraries via the Arduino IDE Library Manager, and copy `NextionControl` manually.
+
+3. Open `SmartFuseBox/SmartFuseBox.ino` in the Arduino IDE.
+
+4. Edit `Local.h` to activate the correct board and feature flags (see [Configuration](#configuration)).
+
+5. Select the target board and COM port, then upload.
+
+Full setup walkthrough: [Docs/SETUP.md](Docs/SETUP.md).
+
+---
+
+## Configuration
+
+All hardware-specific configuration is isolated in a single file: `SmartFuseBox/Local.h`. No other file requires modification for a standard hardware setup.
+
+### Board Selection
+
+Exactly one board define must be active. Remove the trailing underscore to activate:
+
+```cpp
+#define ARDUINO_UNO_R4       // Arduino Uno R4 WiFi
+#define ARDUINO_R4_MINIMA_   // Arduino Uno R4 Minima (inactive)
+#define ESP32_NODE_32_       // ESP32 NodeMCU-32 (inactive)
 ```
-SmartFuseBox/      ← Fuse box firmware (relays, sensors, WiFi, BLE, MQTT)
-BoatControlPanel/  ← Control panel firmware (Nextion display, immobiliser)
-Shared/            ← Common command handlers, sensors, config, utilities
+
+### Feature Flags
+
+| Define | Default | Approx. Flash | Description |
+|---|---|---|---|
+| `FUSE_BOX_CONTROLLER` | Active | — | Enables the full SFB subsystem stack |
+| `WIFI_SUPPORT` | Active | — | WiFi controller and HTTP REST API |
+| `MQTT_SUPPORT` | Active | ~40 KB | MQTT client and HA auto-discovery (requires `WIFI_SUPPORT`) |
+| `BLUETOOTH_SUPPORT` | Inactive | ~144 KB | BLE services (mutually exclusive with WiFi on Uno R4) |
+| `SD_CARD_SUPPORT` | Active | ~32 KB | SD card logger and SPI driver |
+| `NEXTION_DISPLAY_DEVICE` | Active | ~52 KB | Nextion display page system |
+| `OTA_AUTO_UPDATE` | Active | ~165 KB | GitHub OTA (ESP32 + WiFi only) |
+| `LED_MANAGER` | Inactive | — | Arduino R4 WiFi LED matrix (experimental) |
+| `CARD_CONFIG_LOADER` | Inactive | — | Load config overrides from SD `config.txt` at boot |
+
+### Relay Count
+
+```cpp
+constexpr uint8_t ConfigRelayCount = 8;  // number of relay channels
 ```
 
-The SFB firmware is built around `SmartFuseBoxApp`, which owns all subsystems and wires them together at startup. Communication uses a text-based serial command protocol (`COMMAND:key=value;key=value\n`) over two serial ports — one to the BCP and one to a USB debug monitor.
+Pins are assigned at runtime via the `R11` serial command and persisted to EEPROM. `0xFF` marks a pin as unassigned.
+
+Full configuration reference: [Docs/Local.md](Docs/Local.md).
+
+---
+
+## Usage
+
+### Serial / USB Commands (Quick Reference)
+
+Commands follow the frame format: `<CMD>:<key>=<value>;<key>=<value>\n`
+
+```
+# Save config to EEPROM
+C0
+
+# Enable WiFi in client mode, set SSID and password
+C11:v=1
+C12:v=1
+C13:YourSSID
+C14:YourPassword
+C0
+
+# Switch relay 0 on / off
+R3:i=0;v=1
+R3:i=0;v=0
+
+# Query all relay states
+R2
+
+# Read temperature and humidity
+S0
+S1
+
+# Enable MQTT and set broker
+M0:v=1
+M1:192.168.1.100
+C0
+
+# Enable Home Assistant auto-discovery
+M6:v=1
+
+# Query OTA status (ESP32 only)
+F13
+
+# Check for firmware update
+F12
+
+# Apply firmware update immediately
+F12:apply=1
+```
+
+Full command reference (all groups, all parameters): [Docs/Commands.md](Docs/Commands.md).
+
+### HTTP REST API (WiFi)
+
+```
+# Relay control
+POST /api/relay/R3?i=0&v=1
+
+# Sensor data
+GET /api/sensor/S0
+
+# System status
+GET /api/system/F2
+
+# OTA status
+GET /api/system/F13
+```
+
+---
+
+## Subsystem Reference
+
+| Document | Contents |
+|---|---|
+| [Docs/Commands.md](Docs/Commands.md) | Full serial and REST command reference (all groups F, C, R, H, W, S, M, N, E, T) |
+| [Docs/Local.md](Docs/Local.md) | `Local.h` configuration reference: board selection, feature flags, pin layout |
+| [Docs/Sensors.md](Docs/Sensors.md) | Sensor classes, poll intervals, MQTT channels, warning behaviour, extensibility guide |
+| [Docs/Warnings.md](Docs/Warnings.md) | 32-bit warning type reference, `WarningManager` API, propagation model |
+| [Docs/Wifi.md](Docs/Wifi.md) | WiFi architecture: connection state machine, persistent connection model, handler pattern |
+| [Docs/BluetoothBle.md](Docs/BluetoothBle.md) | BLE service/characteristic reference, connection model, adding new services |
+| [Docs/ScheduleEvents.md](Docs/ScheduleEvents.md) | Scheduler data structures, trigger/condition/action types, EEPROM layout |
+| [Docs/MessageBus.md](Docs/MessageBus.md) | Event reference, publish/subscribe API |
+| [Docs/SETUP.md](Docs/SETUP.md) | Prerequisites, library installation, build instructions |
+| [Docs/BOM.md](Docs/BOM.md) | Bill of materials: hardware, fasteners, connectors, 3D-printed parts |
+
+---
+
+## Limitations and Known Issues
+
+- **Arduino Uno R4 WiFi**: WiFi and BLE cannot operate simultaneously due to the shared RF hardware path. This is enforced at compile time.
+- **Arduino Uno R4 Minima**: No radio support. Serial, sensors, and Nextion display only.
+- **OTA updates**: Restricted to ESP32 targets with WiFi in client mode and `OTA_AUTO_UPDATE` defined. Not available on Arduino Uno R4.
+- **Scheduler capacity**: Limited to 6 events on boards with 1 KB or less of EEPROM.
+- **LED matrix manager** (`LED_MANAGER`): Experimental on Arduino R4 WiFi; not recommended for production use.
+- **SD card support**: Marked experimental in `Local.h`. SPI pin configuration must be correct or `SpiPinConfigError` is raised.
+- **Single BLE client**: Only one BLE central can be connected at a time. No pairing or bonding is implemented.
 
 ---
 
-## 🚀 Quick Start
+## Documentation
 
-1. **Read the setup guide** → [Docs/SETUP.md](Docs/SETUP.md) — covers prerequisites, symlinks, and building.
-2. **Configure your board** → edit `Local.h` to select your board, set pin numbers, relay count, and enable features such as `MQTT_SUPPORT` or `WIFI_SUPPORT`.
-3. **Flash the SFB sketch** → open `SmartFuseBox/SmartFuseBox.ino` in the Arduino IDE and upload.
-4. **Configure WiFi** → send serial commands (`C11:v=1`, `C13:YourSSID`, `C14:YourPassword`) or use the BCP touchscreen.
-5. **Connect to Home Assistant** → enable MQTT (`M0:v=1`), set your broker address (`M1:192.168.x.x`), and enable discovery (`M6:v=1`). All sensors and relays appear automatically.
+| Getting Started | Configuration | Connectivity |
+|:---|:---|:---|
+| [Setup Guide](Docs/SETUP.md) | [Local.h Reference](Docs/Local.md) | [WiFi Architecture](Docs/Wifi.md) |
+| [Bill of Materials](Docs/BOM.md) | [Scheduled Events](Docs/ScheduleEvents.md) | [Bluetooth BLE](Docs/BluetoothBle.md) |
+| [Sensor Reference](Docs/Sensors.md) | [Warning System](Docs/Warnings.md) | [Message Bus](Docs/MessageBus.md) |
+| [Command Reference](Docs/Commands.md) | | |
 
 ---
 
-## 🗂️ Documentation
+## License
 
-| 🚀 Getting Started | ⚙️ Configuration | 📡 Connectivity |
-|:---:|:---:|:---:|
-| [📋 Setup Guide](Docs/SETUP.md) | [🔧 Local.h Reference](Docs/Local.md) | [📶 WiFi Architecture](Docs/Wifi.md) |
-| [🔩 Bill of Materials](Docs/BOM.md) | [📅 Scheduled Events](Docs/ScheduleEvents.md) | [📡 Bluetooth BLE](Docs/BluetoothBle.md) |
-| [🔬 Sensor Reference](Docs/Sensors.md) | [⚠️ Warning System](Docs/Warnings.md) | [🗃️ Message Bus](Docs/MessageBus.md) |
+SmartFuseBox is released under the **GNU General Public License v3.0**.  
+See [LICENSE](LICENSE) for the full licence text.
 
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+Copyright &copy; 2025 Simon Carter (`s1cart3r@gmail.com`)
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