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+# Feature Specification: Hardware Abstraction
+# Feature ID: F-HW (F-HW-001 to F-HW-002)
+
+**Document Type:** Feature Specification  
+**Version:** 1.0  
+**Date:** 2025-01-19  
+**Feature Category:** Hardware Abstraction  
+
+## 1. Feature Overview
+
+### 1.1 Feature Purpose
+
+The Hardware Abstraction feature provides a clean separation between application logic and hardware interfaces for the ASF Sensor Hub. This feature ensures hardware independence, maintainability, and testability by abstracting all hardware access through well-defined interfaces and preventing direct hardware access from the application layer.
+
+### 1.2 Feature Scope
+
+**In Scope:**
+- Sensor Abstraction Layer (SAL) for uniform sensor access
+- Hardware interface abstraction for I2C, SPI, UART, ADC, GPIO
+- Storage interface abstraction for SD Card and NVM
+- Display and user interface abstraction
+- GPIO discipline enforcement and resource conflict detection
+
+**Out of Scope:**
+- Hardware driver implementation details (delegated to ESP-IDF)
+- Hardware-specific performance optimizations
+- Physical hardware design and pin assignments
+- Low-level hardware debugging interfaces
+
+## 2. Sub-Features
+
+### 2.1 F-HW-001: Sensor Abstraction Layer (SAL)
+
+**Description:** Comprehensive sensor abstraction layer providing uniform access to all sensor types while maintaining hardware independence and enabling runtime sensor management.
+
+**Sensor Abstraction Interface:**
+```c
+typedef struct {
+    uint8_t sensor_id;               // Unique sensor identifier
+    sensor_type_t type;              // Sensor type enumeration
+    char name[32];                   // Human-readable sensor name
+    char unit[8];                    // Measurement unit (°C, %, ppm, etc.)
+    float min_value;                 // Minimum valid measurement
+    float max_value;                 // Maximum valid measurement
+    float accuracy;                  // Sensor accuracy specification
+    uint32_t warmup_time_ms;         // Required warmup time
+    uint32_t sampling_interval_ms;   // Minimum sampling interval
+    sensor_interface_t interface;    // Hardware interface type
+} sensor_metadata_t;
+
+typedef enum {
+    SENSOR_TYPE_TEMPERATURE = 0,     // Temperature sensors
+    SENSOR_TYPE_HUMIDITY = 1,        // Humidity sensors
+    SENSOR_TYPE_CO2 = 2,            // Carbon dioxide sensors
+    SENSOR_TYPE_AMMONIA = 3,        // Ammonia sensors
+    SENSOR_TYPE_VOC = 4,            // Volatile organic compounds
+    SENSOR_TYPE_LIGHT = 5,          // Light intensity sensors
+    SENSOR_TYPE_PARTICULATE = 6     // Particulate matter sensors
+} sensor_type_t;
+
+typedef enum {
+    SENSOR_INTERFACE_I2C = 0,       // I2C interface
+    SENSOR_INTERFACE_SPI = 1,       // SPI interface
+    SENSOR_INTERFACE_UART = 2,      // UART interface
+    SENSOR_INTERFACE_ADC = 3,       // Analog ADC interface
+    SENSOR_INTERFACE_GPIO = 4       // Digital GPIO interface
+} sensor_interface_t;
+```
+
+**Sensor State Management:**
+```c
+typedef enum {
+    SENSOR_STATE_UNKNOWN = 0,       // Initial state, not detected
+    SENSOR_STATE_DETECTED = 1,      // Presence confirmed
+    SENSOR_STATE_INITIALIZED = 2,   // Driver loaded and configured
+    SENSOR_STATE_WARMUP = 3,        // Warming up, not stable
+    SENSOR_STATE_STABLE = 4,        // Operational and stable
+    SENSOR_STATE_ENABLED = 5,       // Active data acquisition
+    SENSOR_STATE_DISABLED = 6,      // Present but not acquiring
+    SENSOR_STATE_DEGRADED = 7,      // Operational but degraded
+    SENSOR_STATE_FAULTY = 8,        // Detected failure condition
+    SENSOR_STATE_REMOVED = 9        // Previously present, now absent
+} sensor_state_t;
+
+typedef struct {
+    sensor_state_t current_state;    // Current sensor state
+    sensor_state_t previous_state;   // Previous sensor state
+    uint64_t state_change_time;      // Last state change timestamp
+    uint32_t state_change_count;     // Total state changes
+    uint32_t fault_count;            // Number of faults detected
+    uint32_t recovery_count;         // Number of successful recoveries
+    float last_valid_reading;        // Last known good reading
+    uint64_t last_reading_time;      // Timestamp of last reading
+} sensor_state_info_t;
+```
+
+**Sensor State Machine:**
+```mermaid
+stateDiagram-v2
+    [*] --> UNKNOWN
+    UNKNOWN --> DETECTED : Presence detected
+    DETECTED --> INITIALIZED : Driver loaded
+    INITIALIZED --> WARMUP : Acquisition started
+    WARMUP --> STABLE : Warmup complete
+    STABLE --> ENABLED : Enable command
+    ENABLED --> DISABLED : Disable command
+    DISABLED --> ENABLED : Enable command
+    ENABLED --> DEGRADED : Performance degradation
+    DEGRADED --> ENABLED : Performance restored
+    ENABLED --> FAULTY : Failure detected
+    DEGRADED --> FAULTY : Failure detected
+    FAULTY --> ENABLED : Recovery successful
+    FAULTY --> REMOVED : Hardware removed
+    ENABLED --> REMOVED : Hardware removed
+    DISABLED --> REMOVED : Hardware removed
+    DEGRADED --> REMOVED : Hardware removed
+    REMOVED --> DETECTED : Hardware restored
+```
+
+**Uniform Sensor API:**
+```c
+// Sensor lifecycle management
+bool sal_initializeSensor(uint8_t sensor_id);
+bool sal_enableSensor(uint8_t sensor_id);
+bool sal_disableSensor(uint8_t sensor_id);
+bool sal_resetSensor(uint8_t sensor_id);
+
+// Sensor data operations
+bool sal_readSensor(uint8_t sensor_id, float* value);
+bool sal_calibrateSensor(uint8_t sensor_id, const calibration_data_t* cal_data);
+bool sal_validateReading(uint8_t sensor_id, float value);
+bool sal_performHealthCheck(uint8_t sensor_id);
+
+// Sensor information and status
+bool sal_getSensorMetadata(uint8_t sensor_id, sensor_metadata_t* metadata);
+sensor_state_t sal_getSensorState(uint8_t sensor_id);
+bool sal_getSensorStateInfo(uint8_t sensor_id, sensor_state_info_t* info);
+bool sal_isSensorPresent(uint8_t sensor_id);
+bool sal_isSensorHealthy(uint8_t sensor_id);
+```
+
+**Sensor Driver Interface:**
+```c
+typedef struct {
+    // Driver identification
+    char driver_name[32];            // Driver name
+    char driver_version[16];         // Driver version
+    sensor_type_t supported_type;    // Supported sensor type
+    
+    // Driver operations
+    bool (*initialize)(uint8_t sensor_id);
+    bool (*read_raw)(uint8_t sensor_id, uint32_t* raw_value);
+    bool (*convert_value)(uint32_t raw_value, float* converted_value);
+    bool (*calibrate)(uint8_t sensor_id, const calibration_data_t* cal_data);
+    bool (*health_check)(uint8_t sensor_id);
+    bool (*reset)(uint8_t sensor_id);
+    
+    // Driver configuration
+    sensor_metadata_t metadata;     // Sensor metadata
+    void* driver_config;            // Driver-specific configuration
+} sensor_driver_interface_t;
+```
+
+### 2.2 F-HW-002: Hardware Interface Abstraction
+
+**Description:** Comprehensive abstraction of all hardware interfaces to prevent direct hardware access from the application layer and ensure consistent interface usage across the system.
+
+**GPIO Discipline and Management:**
+```c
+typedef struct {
+    uint8_t gpio_number;            // Physical GPIO pin number
+    gpio_function_t function;       // Assigned function
+    gpio_direction_t direction;     // Input/Output direction
+    gpio_pull_t pull_config;        // Pull-up/Pull-down configuration
+    bool is_strapping_pin;          // Strapping pin flag
+    bool is_reserved;               // Reserved for system use
+    char assigned_component[32];    // Component using this GPIO
+} gpio_pin_config_t;
+
+typedef enum {
+    GPIO_FUNC_UNUSED = 0,           // Pin not used
+    GPIO_FUNC_I2C_SDA = 1,         // I2C data line
+    GPIO_FUNC_I2C_SCL = 2,         // I2C clock line
+    GPIO_FUNC_SPI_MOSI = 3,        // SPI master out, slave in
+    GPIO_FUNC_SPI_MISO = 4,        // SPI master in, slave out
+    GPIO_FUNC_SPI_CLK = 5,         // SPI clock
+    GPIO_FUNC_SPI_CS = 6,          // SPI chip select
+    GPIO_FUNC_UART_TX = 7,         // UART transmit
+    GPIO_FUNC_UART_RX = 8,         // UART receive
+    GPIO_FUNC_ADC_INPUT = 9,       // ADC analog input
+    GPIO_FUNC_DIGITAL_INPUT = 10,  // Digital input
+    GPIO_FUNC_DIGITAL_OUTPUT = 11, // Digital output
+    GPIO_FUNC_PWM_OUTPUT = 12      // PWM output
+} gpio_function_t;
+
+// Strapping pins that must be avoided for general-purpose I/O
+#define GPIO_STRAPPING_PINS {0, 3, 45, 46}
+```
+
+**I2C Interface Abstraction:**
+```c
+typedef struct {
+    uint8_t i2c_port;               // I2C port number (0 or 1)
+    uint8_t sda_pin;                // SDA pin assignment
+    uint8_t scl_pin;                // SCL pin assignment
+    uint32_t frequency_hz;          // I2C frequency (100kHz, 400kHz)
+    bool pullup_enabled;            // Internal pull-up enable
+    uint32_t timeout_ms;            // Transaction timeout
+} i2c_config_t;
+
+// I2C abstraction API
+bool hw_i2c_initialize(uint8_t port, const i2c_config_t* config);
+bool hw_i2c_write(uint8_t port, uint8_t device_addr, const uint8_t* data, size_t len);
+bool hw_i2c_read(uint8_t port, uint8_t device_addr, uint8_t* data, size_t len);
+bool hw_i2c_write_read(uint8_t port, uint8_t device_addr, 
+                      const uint8_t* write_data, size_t write_len,
+                      uint8_t* read_data, size_t read_len);
+bool hw_i2c_scan_devices(uint8_t port, uint8_t* found_devices, size_t* count);
+```
+
+**SPI Interface Abstraction:**
+```c
+typedef struct {
+    uint8_t spi_host;               // SPI host (SPI2_HOST, SPI3_HOST)
+    uint8_t mosi_pin;               // MOSI pin assignment
+    uint8_t miso_pin;               // MISO pin assignment
+    uint8_t sclk_pin;               // Clock pin assignment
+    uint8_t cs_pin;                 // Chip select pin
+    uint32_t frequency_hz;          // SPI frequency
+    uint8_t mode;                   // SPI mode (0-3)
+    uint8_t bit_order;              // MSB/LSB first
+} spi_config_t;
+
+// SPI abstraction API
+bool hw_spi_initialize(uint8_t host, const spi_config_t* config);
+bool hw_spi_transmit(uint8_t host, const uint8_t* tx_data, size_t len);
+bool hw_spi_receive(uint8_t host, uint8_t* rx_data, size_t len);
+bool hw_spi_transmit_receive(uint8_t host, const uint8_t* tx_data, 
+                            uint8_t* rx_data, size_t len);
+```
+
+**ADC Interface Abstraction:**
+```c
+typedef struct {
+    adc_unit_t adc_unit;            // ADC1 or ADC2 (ADC1 only when Wi-Fi active)
+    adc_channel_t channel;          // ADC channel
+    adc_atten_t attenuation;        // Input attenuation
+    adc_bitwidth_t resolution;      // ADC resolution
+    uint32_t sample_count;          // Samples for averaging
+} adc_config_t;
+
+// ADC abstraction API
+bool hw_adc_initialize(const adc_config_t* config);
+bool hw_adc_read_raw(adc_unit_t unit, adc_channel_t channel, uint32_t* raw_value);
+bool hw_adc_read_voltage(adc_unit_t unit, adc_channel_t channel, float* voltage);
+bool hw_adc_calibrate(adc_unit_t unit, adc_channel_t channel);
+```
+
+**Storage Interface Abstraction:**
+```c
+// SD Card abstraction
+typedef struct {
+    uint8_t mosi_pin;               // SD card MOSI pin
+    uint8_t miso_pin;               // SD card MISO pin
+    uint8_t clk_pin;                // SD card clock pin
+    uint8_t cs_pin;                 // SD card chip select pin
+    uint32_t frequency_hz;          // SD card SPI frequency
+    bool format_if_mount_failed;    // Auto-format on mount failure
+} sd_card_config_t;
+
+bool hw_sd_initialize(const sd_card_config_t* config);
+bool hw_sd_mount(const char* mount_point);
+bool hw_sd_unmount(void);
+bool hw_sd_get_info(sd_card_info_t* info);
+
+// NVM (NVS) abstraction
+bool hw_nvs_initialize(void);
+bool hw_nvs_write_blob(const char* namespace, const char* key, 
+                      const void* data, size_t size);
+bool hw_nvs_read_blob(const char* namespace, const char* key, 
+                     void* data, size_t* size);
+bool hw_nvs_erase_key(const char* namespace, const char* key);
+bool hw_nvs_get_stats(nvs_stats_t* stats);
+```
+
+**GPIO Map Management:**
+```c
+typedef struct {
+    gpio_pin_config_t pins[GPIO_NUM_MAX]; // All GPIO pin configurations
+    uint32_t used_pin_count;              // Number of used pins
+    uint32_t conflict_count;              // Number of detected conflicts
+    bool map_validated;                   // GPIO map validation status
+} gpio_map_t;
+
+// GPIO map management API
+bool hw_gpio_initialize_map(void);
+bool hw_gpio_reserve_pin(uint8_t gpio_num, gpio_function_t function, 
+                        const char* component_name);
+bool hw_gpio_release_pin(uint8_t gpio_num);
+bool hw_gpio_validate_map(void);
+bool hw_gpio_detect_conflicts(gpio_conflict_t* conflicts, size_t* count);
+bool hw_gpio_get_map(gpio_map_t* map);
+```
+
+**Hardware Resource Conflict Detection:**
+```c
+typedef enum {
+    HW_CONFLICT_GPIO_DUPLICATE = 0,  // Same GPIO used by multiple components
+    HW_CONFLICT_I2C_ADDRESS = 1,     // I2C address conflict
+    HW_CONFLICT_SPI_CS = 2,          // SPI chip select conflict
+    HW_CONFLICT_ADC_WIFI = 3,        // ADC2 used with Wi-Fi active
+    HW_CONFLICT_STRAPPING_PIN = 4,   // Strapping pin used for I/O
+    HW_CONFLICT_POWER_DOMAIN = 5     // Power domain conflict
+} hw_conflict_type_t;
+
+typedef struct {
+    hw_conflict_type_t type;         // Conflict type
+    uint8_t resource_id;             // Conflicting resource ID
+    char component1[32];             // First component involved
+    char component2[32];             // Second component involved
+    char description[128];           // Human-readable description
+} hw_conflict_t;
+```
+
+## 3. Requirements Coverage
+
+### 3.1 System Requirements (SR-XXX)
+
+| Feature | System Requirements | Description |
+|---------|-------------------|-------------|
+| **F-HW-001** | SR-HW-001, SR-HW-002, SR-HW-003, SR-HW-004 | Sensor abstraction layer and state management |
+| **F-HW-002** | SR-HW-005, SR-HW-006, SR-HW-007, SR-HW-008 | Hardware interface abstraction and GPIO discipline |
+
+### 3.2 Software Requirements (SWR-XXX)
+
+| Feature | Software Requirements | Implementation Details |
+|---------|---------------------|----------------------|
+| **F-HW-001** | SWR-HW-001, SWR-HW-002, SWR-HW-003 | SAL interface, sensor drivers, state machine |
+| **F-HW-002** | SWR-HW-004, SWR-HW-005, SWR-HW-006 | Interface abstraction, GPIO management, conflict detection |
+
+## 4. Component Implementation Mapping
+
+### 4.1 Primary Components
+
+| Component | Responsibility | Location |
+|-----------|---------------|----------|
+| **Sensor Abstraction Layer** | Uniform sensor interface, state management | `drivers/sensor_abstraction/` |
+| **Hardware Interface Manager** | Interface abstraction, resource management | `drivers/hw_interface_mgr/` |
+| **GPIO Manager** | GPIO discipline, conflict detection | `drivers/gpio_manager/` |
+| **Sensor Drivers** | Hardware-specific sensor implementations | `drivers/sensors/` |
+
+### 4.2 Supporting Components
+
+| Component | Support Role | Interface |
+|-----------|-------------|-----------|
+| **ESP-IDF Wrappers** | Low-level hardware access | `ESP_IDF_FW_wrappers/` |
+| **Diagnostics** | Hardware fault reporting | `application_layer/diag_task/` |
+| **Machine Constant Manager** | Hardware configuration management | `application_layer/business_stack/machine_constant_manager/` |
+
+### 4.3 Component Interaction Diagram
+
+```mermaid
+graph TB
+    subgraph "Hardware Abstraction Feature"
+        SAL[Sensor Abstraction Layer]
+        HW_MGR[Hardware Interface Manager]
+        GPIO_MGR[GPIO Manager]
+        SENSOR_DRV[Sensor Drivers]
+    end
+    
+    subgraph "Application Layer"
+        SENSOR_MGR[Sensor Manager]
+        PERSIST[Persistence]
+        DIAG[Diagnostics]
+    end
+    
+    subgraph "ESP-IDF Wrappers"
+        I2C_WRAP[I2C Wrapper]
+        SPI_WRAP[SPI Wrapper]
+        UART_WRAP[UART Wrapper]
+        ADC_WRAP[ADC Wrapper]
+        GPIO_WRAP[GPIO Wrapper]
+    end
+    
+    subgraph "Physical Hardware"
+        SENSORS[Physical Sensors]
+        SD_CARD[SD Card]
+        OLED[OLED Display]
+        BUTTONS[Buttons]
+    end
+    
+    SENSOR_MGR --> SAL
+    SAL --> SENSOR_DRV
+    SENSOR_DRV --> HW_MGR
+    
+    HW_MGR --> I2C_WRAP
+    HW_MGR --> SPI_WRAP
+    HW_MGR --> UART_WRAP
+    HW_MGR --> ADC_WRAP
+    
+    GPIO_MGR --> GPIO_WRAP
+    
+    I2C_WRAP --> SENSORS
+    SPI_WRAP --> SD_CARD
+    UART_WRAP --> SENSORS
+    ADC_WRAP --> SENSORS
+    GPIO_WRAP --> BUTTONS
+    GPIO_WRAP --> OLED
+    
+    SAL -.->|Hardware Events| DIAG
+    HW_MGR -.->|Resource Conflicts| DIAG
+```
+
+### 4.4 Sensor Abstraction Flow
+
+```mermaid
+sequenceDiagram
+    participant APP as Application
+    participant SAL as Sensor Abstraction Layer
+    participant DRV as Sensor Driver
+    participant HW as Hardware Interface
+    participant SENSOR as Physical Sensor
+    
+    Note over APP,SENSOR: Sensor Access Through Abstraction
+    
+    APP->>SAL: sal_readSensor(sensor_id)
+    SAL->>SAL: validateSensorState(sensor_id)
+    
+    alt Sensor State Valid
+        SAL->>DRV: driver_read_raw(sensor_id)
+        DRV->>HW: hw_i2c_read(port, addr, data)
+        HW->>SENSOR: I2C transaction
+        SENSOR-->>HW: sensor_data
+        HW-->>DRV: raw_value
+        DRV->>DRV: convert_value(raw_value)
+        DRV-->>SAL: converted_value
+        SAL->>SAL: validateReading(converted_value)
+        SAL-->>APP: sensor_reading
+    else Sensor State Invalid
+        SAL->>SAL: attemptSensorRecovery(sensor_id)
+        SAL-->>APP: error_sensor_not_ready
+    end
+```
+
+## 5. Feature Behavior
+
+### 5.1 Normal Operation Flow
+
+1. **System Initialization:**
+   - Initialize GPIO map and validate pin assignments
+   - Detect hardware resource conflicts and report violations
+   - Initialize hardware interface abstractions (I2C, SPI, UART, ADC)
+   - Scan for connected sensors and initialize sensor drivers
+   - Establish sensor abstraction layer and state management
+
+2. **Sensor Management:**
+   - Maintain sensor state machine for all detected sensors
+   - Provide uniform access interface regardless of hardware interface
+   - Handle sensor failures and recovery attempts
+   - Monitor sensor health and performance metrics
+
+3. **Hardware Interface Management:**
+   - Enforce GPIO discipline and prevent strapping pin usage
+   - Manage shared resources and prevent conflicts
+   - Provide consistent interface abstraction across all hardware types
+   - Monitor interface health and detect hardware failures
+
+4. **Resource Conflict Prevention:**
+   - Validate GPIO assignments during initialization
+   - Detect and report hardware resource conflicts
+   - Enforce ADC1/ADC2 separation when Wi-Fi is active
+   - Maintain canonical GPIO map as single source of truth
+
+### 5.2 Error Handling
+
+| Error Condition | Detection Method | Response Action |
+|----------------|------------------|-----------------|
+| **GPIO Conflict** | Pin assignment validation | Report conflict, prevent initialization |
+| **Sensor Communication Failure** | Interface timeout/error | Mark sensor as faulty, attempt recovery |
+| **Hardware Interface Failure** | Transaction failure | Report hardware fault, disable interface |
+| **Strapping Pin Usage** | GPIO map validation | Prevent usage, report configuration error |
+| **ADC2/Wi-Fi Conflict** | Resource validation | Force ADC1 usage, report conflict |
+| **I2C Address Conflict** | Device scanning | Report conflict, disable conflicting devices |
+
+### 5.3 State-Dependent Behavior
+
+| System State | Feature Behavior |
+|-------------|------------------|
+| **INIT** | Initialize hardware abstractions, detect sensors |
+| **RUNNING** | Full hardware abstraction, continuous sensor monitoring |
+| **WARNING** | Enhanced hardware monitoring, sensor health checks |
+| **FAULT** | Critical hardware functions only, preserve sensor states |
+| **OTA_UPDATE** | Maintain hardware state, suspend sensor operations |
+| **TEARDOWN** | Graceful hardware shutdown, preserve configurations |
+| **SERVICE** | Limited hardware access for diagnostics |
+| **SD_DEGRADED** | Continue sensor operations, report storage degradation |
+
+## 6. Feature Constraints
+
+### 6.1 Timing Constraints
+
+- **Sensor State Transitions:** Maximum 100ms for state changes
+- **Hardware Interface Operations:** Bounded timeouts for all transactions
+- **GPIO Conflict Detection:** Complete during system initialization
+- **Sensor Recovery Attempts:** Maximum 3 attempts with exponential backoff
+
+### 6.2 Resource Constraints
+
+- **GPIO Usage:** Enforce strapping pin restrictions and conflict prevention
+- **I2C Pull-ups:** Physical pull-ups required (2.2kΩ - 4.7kΩ for 3.3V)
+- **ADC Constraints:** ADC1 only when Wi-Fi active, ADC2 when Wi-Fi inactive
+- **Memory Usage:** Maximum 32KB for abstraction layer buffers and state
+
+### 6.3 Hardware Constraints
+
+- **ESP32-S3 Limitations:** Respect hardware capabilities and restrictions
+- **Interface Speeds:** I2C up to 400kHz, SPI up to 80MHz
+- **Voltage Levels:** 3.3V logic levels for all interfaces
+- **Current Limitations:** Respect GPIO current drive capabilities
+
+## 7. Interface Specifications
+
+### 7.1 Sensor Abstraction Layer API
+
+```c
+// SAL initialization and management
+bool sal_initialize(void);
+bool sal_detectSensors(void);
+bool sal_getSensorCount(uint8_t* count);
+bool sal_getSensorList(uint8_t* sensor_ids, size_t* count);
+
+// Sensor operations
+bool sal_readSensor(uint8_t sensor_id, float* value);
+bool sal_readMultipleSensors(uint8_t* sensor_ids, size_t count, 
+                            sensor_reading_t* readings);
+bool sal_calibrateSensor(uint8_t sensor_id, const calibration_data_t* cal_data);
+bool sal_resetSensor(uint8_t sensor_id);
+
+// Sensor state and health
+sensor_state_t sal_getSensorState(uint8_t sensor_id);
+bool sal_getSensorHealth(uint8_t sensor_id, sensor_health_t* health);
+bool sal_performSensorDiagnostics(uint8_t sensor_id, sensor_diagnostics_t* diag);
+```
+
+### 7.2 Hardware Interface Manager API
+
+```c
+// Interface initialization
+bool hwMgr_initialize(void);
+bool hwMgr_initializeI2C(uint8_t port, const i2c_config_t* config);
+bool hwMgr_initializeSPI(uint8_t host, const spi_config_t* config);
+bool hwMgr_initializeUART(uint8_t port, const uart_config_t* config);
+bool hwMgr_initializeADC(const adc_config_t* config);
+
+// Resource management
+bool hwMgr_reserveResource(hw_resource_type_t type, uint8_t resource_id, 
+                          const char* component_name);
+bool hwMgr_releaseResource(hw_resource_type_t type, uint8_t resource_id);
+bool hwMgr_validateResources(void);
+bool hwMgr_getResourceConflicts(hw_conflict_t* conflicts, size_t* count);
+```
+
+### 7.3 GPIO Manager API
+
+```c
+// GPIO management
+bool gpioMgr_initialize(void);
+bool gpioMgr_reservePin(uint8_t gpio_num, gpio_function_t function, 
+                       const char* component_name);
+bool gpioMgr_releasePin(uint8_t gpio_num);
+bool gpioMgr_configurePin(uint8_t gpio_num, const gpio_config_t* config);
+
+// GPIO validation and conflict detection
+bool gpioMgr_validateGPIOMap(void);
+bool gpioMgr_isStrappingPin(uint8_t gpio_num);
+bool gpioMgr_detectConflicts(gpio_conflict_t* conflicts, size_t* count);
+bool gpioMgr_getGPIOMap(gpio_map_t* map);
+```
+
+## 8. Testing and Validation
+
+### 8.1 Unit Testing
+
+- **Sensor Abstraction:** All sensor types and state transitions
+- **Interface Abstraction:** I2C, SPI, UART, ADC operations
+- **GPIO Management:** Pin assignment and conflict detection
+- **Resource Management:** Resource allocation and validation
+
+### 8.2 Integration Testing
+
+- **Cross-Interface Testing:** Multiple interfaces operating simultaneously
+- **Sensor Integration:** All sensor types through abstraction layer
+- **Resource Conflict Testing:** Deliberate conflict scenarios
+- **State Coordination:** Hardware abstraction with system states
+
+### 8.3 System Testing
+
+- **Hardware Compatibility:** All supported sensor hardware configurations
+- **Performance Testing:** Interface throughput and timing constraints
+- **Fault Injection:** Hardware failure simulation and recovery
+- **Long-Duration Testing:** Extended operation with hardware monitoring
+
+### 8.4 Acceptance Criteria
+
+- All sensor types accessible through uniform SAL interface
+- Hardware interfaces properly abstracted from application layer
+- GPIO conflicts detected and prevented during initialization
+- No direct hardware access from application components
+- Sensor state management operates correctly under all conditions
+- Hardware resource conflicts properly detected and reported
+- Complete hardware abstraction maintains system performance
+
+## 9. Dependencies
+
+### 9.1 Internal Dependencies
+
+- **Sensor Manager:** Primary consumer of sensor abstraction layer
+- **Diagnostics:** Hardware fault reporting and event logging
+- **Machine Constant Manager:** Hardware configuration management
+- **State Manager:** Hardware behavior coordination across system states
+
+### 9.2 External Dependencies
+
+- **ESP-IDF Framework:** Low-level hardware drivers and HAL
+- **Hardware Components:** Physical sensors, interfaces, and peripherals
+- **FreeRTOS:** Task coordination and resource management
+- **Hardware Design:** GPIO assignments and interface configurations
+
+## 10. Future Enhancements
+
+### 10.1 Planned Improvements
+
+- **Dynamic Sensor Discovery:** Runtime sensor detection and configuration
+- **Advanced Sensor Fusion:** Multi-sensor data correlation and validation
+- **Hardware Health Monitoring:** Predictive hardware failure detection
+- **Plug-and-Play Support:** Hot-swappable sensor support
+
+### 10.2 Scalability Considerations
+
+- **Additional Sensor Types:** Framework supports easy sensor type extension
+- **Multiple Interface Support:** Support for additional hardware interfaces
+- **Advanced GPIO Management:** Dynamic GPIO allocation and optimization
+- **Hardware Virtualization:** Virtual hardware interfaces for testing
+
+---
+
+**Document Status:** Final for Implementation Phase  
+**Component Dependencies:** Verified against architecture  
+**Requirements Traceability:** Complete (SR-HW, SWR-HW)  
+**Next Review:** After component implementation