# Feature Engineering Specification ## Persistence & Data Management Features **Feature Group ID:** FG-DATA **Scope:** Sensor Hub (Sub-Hub only) **Target Platform:** ESP32-S3–based Sensor Hub **Applies To:** Indoor poultry farm sensor hubs **Dependencies:** * Sensor Data Acquisition (FG-DAQ) * Data Quality & Calibration (FG-DQC) * Diagnostics & Health Monitoring (FG-DIAG) * System State Management / Teardown Mechanism ## 1\. Purpose and Objectives The **Persistence & Data Management Features** define how the Sensor Hub stores, protects, and manages critical runtime and historical data. These features ensure that: * Sensor data and system state are not lost during resets or failures * Data storage is abstracted from application logic * Critical data is safely handled during firmware updates, configuration changes, or fatal faults The persistence layer is a **foundational system service**, supporting diagnostics, calibration, OTA, and recovery operations. ## 2\. Feature Overview and Relationships

Feature ID

Feature Name

Primary Objective

Related Features

F-DATA-01

Persistent Sensor Data Storage

Store timestamped sensor data

DAQ, COM

F-DATA-02

Data Persistence Abstraction (DP)

Abstract storage access

Application Layer

F-DATA-03

Safe Data Handling During State Transitions

Protect data during teardown

OTA, System Mgmt

## 3\. Functional Feature Descriptions ### 3.1 F-DATA-01: Persistent Sensor Data Storage **Description** The system shall persist timestamped sensor data to non-volatile storage to support historical analysis, diagnostics correlation, and recovery scenarios. Persistence may include: * Filtered sensor values * Timestamps * Sensor validity and status metadata The persistence policy (frequency, retention window, overwrite behavior) is configurable and optimized for storage longevity and performance. **Key Capabilities** * Non-volatile storage (SD card / NVM) * Timestamped records * Configurable retention policy * Integration with DAQ and COM ### 3.2 F-DATA-02: Data Persistence Abstraction (DP Component) **Description** The system shall provide a **Data Persistence (DP) component** that abstracts storage access for all upper layers. Application and feature modules interact with the DP component rather than directly accessing storage hardware. The DP component manages: * Data model definitions * Serialization and deserialization * Storage backend selection * Consistency and integrity guarantees **Key Capabilities** * Unified persistence API * Storage backend abstraction * Centralized data ownership * Reduced coupling between layers ### 3.3 F-DATA-03: Safe Data Handling During State Transitions **Description** The system shall ensure safe and deterministic handling of data during critical state transitions, including: * Firmware updates (OTA) * Machine Constants updates * System resets * Fatal error handling Before entering such transitions, the system executes a controlled data finalization process to flush buffers, persist critical state, and verify data integrity. **Key Capabilities** * Controlled data flush * Atomic write operations * Data integrity checks * Coordination with teardown mechanism ## 4\. System Requirements (Formal SHALL Statements) ### 4.1 Persistent Sensor Data Storage **SR-DATA-001** The system shall persist timestamped sensor data in non-volatile storage. **SR-DATA-002** The system shall store sensor data together with sensor identifiers, timestamps, and validity status. **SR-DATA-003** The system shall support configurable data retention and overwrite policies. ### 4.2 Data Persistence Abstraction (DP Component) **SR-DATA-004** The system shall provide a Data Persistence (DP) component as the sole interface for persistent data access. **SR-DATA-005** The system shall prevent application and feature modules from directly accessing storage hardware. **SR-DATA-006** The DP component shall support serialization and deserialization of structured system data. ### 4.3 Safe Data Handling During State Transitions **SR-DATA-007** The system shall ensure that all critical runtime data is flushed to non-volatile storage before entering a controlled teardown or reset. **SR-DATA-008** The system shall protect data integrity during firmware updates and configuration changes. **SR-DATA-009** The system shall verify successful data persistence before completing a state transition. ### 4.4 Power-Loss Data Protection [NEW] **SR-DATA-010** The system shall detect brownout conditions using hardware brownout detector (BOD) at 3.0V threshold. **SR-DATA-011** The system shall immediately flush critical data buffers to non-volatile storage upon brownout detection. **SR-DATA-012** The system shall complete data flush operations within supercapacitor runtime (1-2 seconds) during brownout. **SR-DATA-013** The system shall implement wear-aware batch writing to prevent SD card wear. ## 5\. Feature ↔ System Requirement Mapping | Feature ID | System Requirements | |------------|---------------------| | F-DATA-01 | SR-DATA-001, SR-DATA-002, SR-DATA-003 | | F-DATA-02 | SR-DATA-004, SR-DATA-005, SR-DATA-006 | | F-DATA-03 | SR-DATA-007, SR-DATA-008, SR-DATA-009 | | F-DATA-04 | SR-DATA-010, SR-DATA-011, SR-DATA-012, SR-DATA-013 | ## 6\. Engineering Notes * The DP component aligns with your **DP Stack** already defined in the architecture. * Atomic write strategies (e.g., temp file + rename) are recommended. * Diagnostic events should be generated on persistence failures. * Storage wear-leveling considerations apply for SD/NVM. ##