PCB box

Sensor Board
All about the sensor board

Overview
A 480MHz Swiss Army knife of the embedded team☮️ 
 Table of Contents 
 Page 1 : Table of Contents & Overview Page 2 : GNSS (GPS) Sensor Page 3 : pH Sensor Page 4 : IMU (Inertial Measurement Unit) Page 5 : Load Cell Sensor Page 6 : Pressure Sensor Page 7: Sensor Basics Utility Library Page 8 : System Architecture & Integration Page 9 : Testin g Page 10 : Configuration Page 11 : Reference 
 Purpose 
 The Sensor Board is a specialized embedded system designed to acquire environmental and motion data from multiple sensors. It integrates position (GNSS), water quality (pH), motion (IMU), force (load cells), and pressure measurements, transmitting all data over Ethernet using Protocol Buffer encoding. 
 Hardware Platform 
 Microcontroller: STM32H753ZI (Nucleo board) Real-Time OS: FreeRTOS with CMSIS-RTOS V2 Communication: Ethernet (LAN8742 PHY) UART (Multiple sensor connections) I2C/SPI (IMU, pressure sensors) Memory: 64KB heap allocated for FreeRTOS Clock: 480 MHz ARM Cortex-M7 
 Key Board Features 
 Multi-sensor fusion with independent sensor threads Network integration via UDP/Ethernet with Protobuf Real-time logging to UART (115200 baud) MAC address filtering for selective communication Packet dispatcher for incoming control signals LED status indicators (Green, Blue, Red) Heap monitoring with critical threshold alerts 
 Core Sensors Integrated 
 GPS (GNSS) - Global positioning and velocity IMU - 3-axis acceleration, rotation, magnetic field pH Sensor - Water quality measurement Load Cells - Force measurement (×2) Pressure Sensors - Pressure measurement (×2)

STM32CubeMX Sensor Configuration
This page documents the current STM32CubeMX configuration for the Sensor Board firmware and explains how to extend it for sensor interfaces (UART/I2C/SPI/ADC) in a way that is safe for code generation. 
 IOC File : components/sensor_board/firmware/firmware.ioc Generated HAL Init Files : components/sensor_board/firmware/Core/Src/ Application Entry : src/sensor_board/main.c 
 Current CubeMX Snapshot 
 Item Value MCU STM32H753ZIT6 (NUCLEO-H753ZI) CubeMX Version 6.15.0 STM32Cube FW Package STM32Cube FW_H7 v1.12.1 Toolchain Makefile + GCC Post-generation Script ../../../scripts/post_code_generation.bash 
 Enabled CubeMX Components 
 CORTEX_M7 (I-Cache/D-Cache enabled, MPU configured) ETH (RMII mode) LWIP (Static IP, DHCP disabled) FREERTOS (CMSIS-RTOS v2, default task generated) TIM1 (base timer) SYS/NVIC/RCC base platform configuration 
 Clock and Core Setup 
 Clock Configuration (from IOC) 
 Parameter Value Clock Source HSE 8 MHz -> PLL SYSCLK 72 MHz APB1 36 MHz (DIV2) APB2/APB3/APB4 72 MHz TIM1 Clock 72 MHz 
 Cortex-M7 / MPU 
 Instruction cache: enabled Data cache: enabled MPU region at 0x30000000 , size 32KB , shareable, non-cacheable 
 Pinout and Peripheral Mapping 
 Ethernet (RMII) 
 Signal Pin ETH_REF_CLK PA1 ETH_MDIO PA2 ETH_CRS_DV PA7 ETH_MDC PC1 ETH_RXD0 PC4 ETH_RXD1 PC5 ETH_TX_EN PG11 ETH_TXD0 PG13 ETH_TXD1 PB13 
 Serial / COM 
 Signal Pin Note USART1_TX PA9 Configured in generated MX_GPIO_Init() USART1_RX PA10 Configured in generated MX_GPIO_Init() USART3_TX PD8 Used by NUCLEO COM path ( MX_USART3_Init in app init) USART3_RX PD9 Used by NUCLEO COM path ( MX_USART3_Init in app init) 
 Board IO / Misc 
 Pin Mode Typical Use PC13 GPIO Input User button PB0 GPIO Output Board output line PB7 GPIO Output Board output line PB14 GPIO Output Board output line PH0 / PH1 HSE oscillator System clock source PC14 / PC15 LSE oscillator Low-speed oscillator 
 Timer, RTOS, and Interrupts 
 TIM1 Base Timer 
 htim1.Init.Prescaler = 6400 - 1;
htim1.Init.Period = 10000; 
 With a 72 MHz timer clock, this gives an update period near 0.89 s. 
 Interrupt Priorities (Key Entries) 
 IRQ Priority Notes ETH_IRQn 15 Ethernet/LwIP path TIM1_UP_IRQn 12 TIM1 update interrupt TIM2_IRQn 7 HAL tick time base EXTI15_10_IRQn 6 External interrupt group 
 Sensor Interface Status 
 What Is Already Configured in CubeMX 
 Networking stack and RMII pinout Base timer and RTOS scaffolding Basic UART-capable pins and NUCLEO COM integration path 
 What Is Not Yet Fully Modeled in CubeMX (TO-DO ONCE sensors retrieved and assembled) 
 Dedicated ADC channels for analog sensors (pH, load cell, pressure) Dedicated I2C/SPI buses for IMU and pressure variants Explicit sensor-specific pin labels and alternate-function assignments 
 Important: Current sensor drivers include placeholders for hardware access in multiple modules. When bringing up physical sensors, add the corresponding CubeMX peripherals first, then update the sensor drivers to use generated handles. 
 Recommended Workflow 
 Open components/sensor_board/firmware/firmware.ioc in STM32CubeMX. Add required peripherals for the target sensor like this: 
 GPS -> USARTx (baud/parity/stop bits to match module)
IMU -> I2Cx or SPIx (+ optional DRDY INT GPIO)
pH -> ADCx channel (sampling time, resolution)
Load Cell -> ADCx channel(s) or external ADC interface
Pressure -> ADCx or I2Cx/SPIx (depends on sensor part) 
 Assign and lock pins in Pinout view; avoid overlap with RMII and COM pins. Configure clocks for new peripherals in Clock Configuration. Set NVIC priorities for new ISR sources so Ethernet/RTOS timing remains stable. Generate code with Keep User Code enabled. Rebuild using PlatformIO and validate startup + sensor polling. 
 Conflict To Look Out for Before Saving .ioc file 
 No conflict with ETH RMII pins (PA1, PA2, PA7, PC1, PC4, PC5, PG11, PG13, PB13) No conflict with debug/COM path (PA9/PA10 and PD8/PD9) No conflict with oscillator pins (PH0, PH1, PC14, PC15) 
 Related Pages 
 Configuration Reference Sensor Basics Utility Library

Sensor Basics Utility Library
These are basic features that could be used if required... But was something made in "spare time" 
 Source Code Location 
 Files: 
 components/sensor_board/sensor_basics/sensor_basics.h - Function declarations and documentation components/sensor_board/sensor_basics/sensor_basics.c - Implementation 
 Dependencies: 
 result.h - Standard result/error code definitions stdint.h - Integer type definitions 
 
 pH Sensor Functions 
 validate_ph_value() 
 Validates if a pH value is within the acceptable range (0-14). 
 /**
 * @brief Validates if a pH value is within the acceptable range (0-14).
 * @param ph_value The pH value to validate.
 * @return RESULT_OK if the value is valid, RESULT_ERR_INVALID_DATA otherwise.
 */
result_t validate_ph_value(float ph_value); 
 Implementation: 
 result_t validate_ph_value(float ph_value) {
 if (ph_value >= 0.0f && ph_value <= 14.0f) {
 return RESULT_OK;
 }
 return RESULT_ERR_INVALID_DATA;
} 
 Parameters: 
 ph_value - Float value to validate (typical range: 0.0 to 14.0) 
 Return Values: 
 RESULT_OK - Value is within valid range RESULT_ERR_INVALID_DATA - Value is outside 0-14 range 
 Usage Example: 
 float ph_reading = ph_sensor.ph_value;

if (validate_ph_value(ph_reading) == RESULT_OK) {
 LOG_INFO("pH sensor valid: %.2f", ph_reading);
 diagnostics.ph_sensor.state = SENSOR_OPERATING;
} else {
 LOG_ERROR("pH out of range: %.2f", ph_reading);
 diagnostics.ph_sensor.state = SENSOR_ERROR;
 diagnostics.ph_sensor.error_code = PHErrorCode_PH_INVALID_DATA;
} 
 
 Temperature Conversion Functions 
 celsius_to_fahrenheit() 
 Converts temperature from Celsius to Fahrenheit. 
 /**
 * @brief Converts temperature from Celsius to Fahrenheit.
 * @param celsius The temperature in Celsius.
 * @param fahrenheit Pointer to a float where the converted Fahrenheit temperature will be stored.
 * @return RESULT_OK on success, or RESULT_ERR_INVALID_ARG if fahrenheit is NULL.
 */
result_t celsius_to_fahrenheit(float celsius, float *fahrenheit); 
 Conversion Formula: °F = (°C × 9/5) + 32 
 Parameters: 
 celsius - Input temperature in Celsius fahrenheit - Pointer to output variable (must not be NULL) 
 Return Values: 
 RESULT_OK - Conversion successful RESULT_ERR_INVALID_ARG - fahrenheit pointer is NULL 
 Status: Currently commented out in implementation 
 Usage Example: 
 float temp_celsius = 25.0f;
float temp_fahrenheit;

if (celsius_to_fahrenheit(temp_celsius, &temp_fahrenheit) == RESULT_OK) {
 LOG_INFO("Temperature: %.1f°C = %.1f°F", temp_celsius, temp_fahrenheit);
} 
 fahrenheit_to_celsius() 
 Converts temperature from Fahrenheit to Celsius. 
 /**
 * @brief Converts temperature from Fahrenheit to Celsius.
 * @param fahrenheit The temperature in Fahrenheit.
 * @param celsius Pointer to a float where the converted Celsius temperature will be stored.
 * @return RESULT_OK on success, or RESULT_ERR_INVALID_ARG if celsius is NULL.
 */
result_t fahrenheit_to_celsius(float fahrenheit, float *celsius); 
 Conversion Formula: °C = (°F - 32) × 5/9 
 Status: Currently commented out in implementation 
 
 IMU (Accelerometer) Functions 
 validate_accelerometer_value() 
 Validates if a single accelerometer value is within the typical range. 
 /**
 * @brief Validates if an accelerometer value is within the typical range.
 * @param accel_value The accelerometer value to validate.
 * @return RESULT_OK if the value is valid, RESULT_ERR_INVALID_DATA otherwise.
 */
result_t validate_accelerometer_value(float accel_value); 
 Implementation: 
 result_t validate_accelerometer_value(float accel_value) {
 if (accel_value >= -160.0f && accel_value <= 160.0f) {
 return RESULT_OK;
 }
 return RESULT_ERR_INVALID_DATA;
} 
 Parameters: 
 accel_value - Single axis acceleration value in m/s² 
 Valid Range: -160.0 to +160.0 m/s² (typical ±16g sensor range) 
 Return Values: 
 RESULT_OK - Value is within valid range RESULT_ERR_INVALID_DATA - Value exceeds acceptable limits 
 Usage Example: 
 float accel_x = imu_data.accel[0];

if (validate_accelerometer_value(accel_x) == RESULT_OK) {
 LOG_DEBUG("Accel X valid: %.2f m/s²", accel_x);
} else {
 LOG_ERROR("Accel X out of range: %.2f m/s²", accel_x);
} 
 validate_imu_data() 
 Validates all three axes of accelerometer data simultaneously. 
 /**
 * @brief Validates all three axes of accelerometer data.
 * @param accel_x The acceleration value for the X-axis.
 * @param accel_y The acceleration value for the Y-axis.
 * @param accel_z The acceleration value for the Z-axis.
 * @return RESULT_OK if all values are valid, RESULT_ERR_INVALID_DATA otherwise.
 */
result_t validate_imu_data(float accel_x, float accel_y, float accel_z); 
 Implementation: 
 result_t validate_imu_data(float accel_x, float accel_y, float accel_z) {
 TRY(validate_accelerometer_value(accel_x));
 TRY(validate_accelerometer_value(accel_y));
 TRY(validate_accelerometer_value(accel_z));
 return RESULT_OK;
} 
 Parameters: 
 accel_x - X-axis acceleration (m/s²) accel_y - Y-axis acceleration (m/s²) accel_z - Z-axis acceleration (m/s²) 
 Return Values: 
 RESULT_OK - All three axes within valid range RESULT_ERR_INVALID_DATA - Any axis exceeds acceptable limits 
 Usage Example: 
 if (validate_imu_data(imu_data.accel[0], imu_data.accel[1], imu_data.accel[2]) == RESULT_OK) {
 LOG_INFO("IMU acceleration valid");
 diagnostics.imu_sensor.state = SENSOR_OPERATING;
} else {
 LOG_ERROR("IMU acceleration out of range");
 diagnostics.imu_sensor.state = SENSOR_ERROR;
} 
 
 Pressure Conversion Functions 
 bar_to_psi() 
 Converts pressure from bar to psi (pounds per square inch). 
 /**
 * @brief Converts pressure from bar to psi.
 * @param bar The pressure in bar.
 * @param psi Pointer to a float where the converted psi pressure will be stored.
 * @return RESULT_OK on success, or RESULT_ERR_INVALID_ARG if psi is NULL.
 */
result_t bar_to_psi(float bar, float *psi); 
 Conversion Formula: psi = bar × 14.5038 
 Parameters: 
 bar - Pressure in bar psi - Pointer to output variable (must not be NULL) 
 Return Values: 
 RESULT_OK - Conversion successful RESULT_ERR_INVALID_ARG - psi pointer is NULL 
 Status: Currently commented out in implementation 
 Usage Example: 
 float pressure_bar = 5.0f;
float pressure_psi;

if (bar_to_psi(pressure_bar, &pressure_psi) == RESULT_OK) {
 LOG_INFO("Pressure: %.2f bar = %.2f psi", pressure_bar, pressure_psi);
} 
 psi_to_bar() 
 Converts pressure from psi to bar. 
 /**
 * @brief Converts pressure from psi to bar.
 * @param psi The pressure in psi.
 * @param bar Pointer to a float where the converted bar pressure will be stored.
 * @return RESULT_OK on success, or RESULT_ERR_INVALID_ARG if bar is NULL.
 */
result_t psi_to_bar(float psi, float *bar); 
 Conversion Formula: bar = psi ÷ 14.5038 
 Status: Currently commented out in implementation 
 
 GPS Functions 
 validate_gps_latitude() 
 Validates GPS latitude value is within valid range. 
 /**
 * @brief Validates GPS latitude value.
 * @param latitude The latitude value to validate (-90 to +90 degrees).
 * @return RESULT_OK if the value is valid, RESULT_ERR_INVALID_DATA otherwise.
 */
result_t validate_gps_latitude(double latitude); 
 Implementation: 
 result_t validate_gps_latitude(double latitude) {
 if (latitude >= -90.0 && latitude <= 90.0) {
 return RESULT_OK;
 }
 return RESULT_ERR_INVALID_DATA;
} 
 Parameters: 
 latitude - Latitude in degrees (double precision) 
 Valid Range: -90.0 to +90.0 degrees 
 Negative = South Positive = North 0° = Equator 
 Return Values: 
 RESULT_OK - Value is within valid range RESULT_ERR_INVALID_DATA - Value outside ±90 degrees 
 validate_gps_longitude() 
 Validates GPS longitude value is within valid range. 
 /**
 * @brief Validates GPS longitude value.
 * @param longitude The longitude value to validate (-180 to +180 degrees).
 * @return RESULT_OK if the value is valid, RESULT_ERR_INVALID_DATA otherwise.
 */
result_t validate_gps_longitude(double longitude); 
 Implementation: 
 result_t validate_gps_longitude(double longitude) {
 if (longitude >= -180.0 && longitude <= 180.0) {
 return RESULT_OK;
 }
 return RESULT_ERR_INVALID_DATA;
} 
 Parameters: 
 longitude - Longitude in degrees (double precision) 
 Valid Range: -180.0 to +180.0 degrees 
 Negative = West Positive = East 0° = Prime Meridian ±180° = International Date Line 
 Return Values: 
 RESULT_OK - Value is within valid range RESULT_ERR_INVALID_DATA - Value outside ±180 degrees 
 validate_gps_hdop() 
 Validates GPS Horizontal Dilution of Precision (HDOP) value. 
 /**
 * @brief Validates GPS HDOP value.
 * @param hdop The HDOP value to validate (0-50 typical range).
 * @return RESULT_OK if the value is valid, RESULT_ERR_INVALID_DATA otherwise.
 */
result_t validate_gps_hdop(float hdop); 
 Implementation: 
 result_t validate_gps_hdop(float hdop) {
 if (hdop >= 0.0f && hdop <= 50.0f) {
 return RESULT_OK;
 }
 return RESULT_ERR_INVALID_DATA;
} 
 Parameters: 
 hdop - Horizontal dilution of precision value 
 Valid Range: 0.0 to 50.0 
 HDOP Quality Interpretation: 
 <1 - Ideal 1-2 - Excellent 2-5 - Good 5-10 - Moderate 10-20 - Fair >20 - Poor 
 Return Values: 
 RESULT_OK - Value is within valid range RESULT_ERR_INVALID_DATA - Value exceeds acceptable limits 
 validate_gps_satellite_count() 
 Validates GPS satellite count is within valid range. 
 /**
 * @brief Validates GPS satellite count.
 * @param satellites The number of satellites to validate.
 * @return RESULT_OK if the value is valid, RESULT_ERR_INVALID_DATA otherwise.
 */
result_t validate_gps_satellite_count(int32_t satellites); 
 Implementation: 
 result_t validate_gps_satellite_count(int32_t satellites) {
 if (satellites >= 0 && satellites <= 30) {
 return RESULT_OK;
 }
 return RESULT_ERR_INVALID_DATA;
} 
 Parameters: 
 satellites - Number of satellites in view 
 Valid Range: 0 to 30 satellites 
 Satellite Count Guidance: 
 0-3 - No/poor fix possible 4-5 - 3D fix possible 6-9 - Good coverage 10+ - Excellent coverage 
 Return Values: 
 RESULT_OK - Value is within valid range RESULT_ERR_INVALID_DATA - Negative value or exceeds 30 
 Usage Example (Full GPS Validation): 
 if (validate_gps_latitude(gps_data.latitude) == RESULT_OK &&
 validate_gps_longitude(gps_data.longitude) == RESULT_OK &&
 validate_gps_hdop(gps_data.hdop) == RESULT_OK &&
 validate_gps_satellite_count(gps_data.satellites) == RESULT_OK) {
 
 LOG_INFO("GPS fix valid: %.6f, %.6f (sats=%d)", 
 gps_data.latitude, gps_data.longitude, gps_data.satellites);
 diagnostics.gps_sensor_1.state = SENSOR_OPERATING;
} else {
 LOG_WARNING("GPS validation failed");
 diagnostics.gps_sensor_1.state = SENSOR_ERROR;
} 
 
 Error Handling Pattern 
 All validation functions follow a consistent pattern: 
 // Check sensor data
if (validate_<sensor>_<field>(value) == RESULT_OK) {
 // Data is valid - use it
 diagnostics.<sensor>.state = SENSOR_OPERATING;
} else {
 // Data is invalid - set error state
 diagnostics.<sensor>.state = SENSOR_ERROR;
 diagnostics.<sensor>.error_code = <ERROR_CODE>_INVALID_DATA;
} 
 TRY Macro Usage: 
 The implementation uses a TRY() macro for error propagation (from result.h): 
 // In validate_imu_data()
result_t validate_imu_data(float accel_x, float accel_y, float accel_z) {
 TRY(validate_accelerometer_value(accel_x)); // Return on error
 TRY(validate_accelerometer_value(accel_y)); // Return on error
 TRY(validate_accelerometer_value(accel_z)); // Return on error
 return RESULT_OK;
} 
 
 Implementation Status 
 Currently Implemented (Active): 
 ✓ validate_ph_value() ✓ validate_accelerometer_value() ✓ validate_imu_data() ✓ validate_gps_latitude() ✓ validate_gps_longitude() ✓ validate_gps_hdop() ✓ validate_gps_satellite_count() 
 Currently Commented Out (Inactive): 
 ⊘ celsius_to_fahrenheit() - Declared but not implemented ⊘ fahrenheit_to_celsius() - Declared but not implemented ⊘ bar_to_psi() - Declared but not implemented ⊘ psi_to_bar() - Declared but not implemented 
 Note: Temperature and pressure conversions are stubbed out in the current implementation. They can be enabled by uncommenting the implementation in sensor_basics.c if needed for future features. 
 
 Testing 
 Test Suite Location: test/sensor_board/test_sensor_basics/ 
 Building Tests: 
 // Run all sensor_basics tests
pio test -e sensor_board -f test_sensor_basics

// Run with verbose output
pio test -e sensor_board -f test_sensor_basics -v 
 Test Coverage: 
 Boundary value testing (min/max ranges) Edge cases (0 values, extreme values) Valid range acceptance Invalid range rejection NULL pointer handling for conversion functions 
 
 Integration in Main Application 
 Typical Usage in main.c: 
 // After polling a sensor
result_t poll_result = poll_gps_sensor(&gps_data);

if (poll_result == RESULT_OK) {
 // Validate all GPS fields before using
 if (validate_gps_latitude(gps_data.latitude) == RESULT_OK &&
 validate_gps_longitude(gps_data.longitude) == RESULT_OK) {
 
 diagnostics.gps_sensor_1.state = SENSOR_OPERATING;
 // Safe to use: gps_data.latitude, gps_data.longitude
 
 } else {
 diagnostics.gps_sensor_1.state = SENSOR_ERROR;
 diagnostics.gps_sensor_1.error_code = GPS_INVALID_DATA;
 }
} else if (poll_result == RESULT_ERR_COMMS) {
 diagnostics.gps_sensor_1.state = SENSOR_ERROR;
 diagnostics.gps_sensor_1.error_code = GPS_COMMUNICATION_FAILURE;
}

Architecture
Complete system overview showing FreeRTOS, sensor polling loop, protobuf encoding, UDP transmission, and memory layout. Includes initialization sequence and error handling strategy. 
 Main Loop Operation 
 while (1) {
 // STEP 1: System Health Check
 // - Check heap (critical: <8KB)
 // - Toggle status LEDs
 // - Send raw Ethernet beacon
 
 // STEP 2: Initialize Diagnostics Message
 SensorBoardDiagnostics diagnostics_msg;
 
 // STEP 3: Poll All Sensors
 // - pH Sensor
 // - GPS Sensor
 // - IMU Sensor
 // - Load Cells (x2)
 // - Pressure Sensors (x2)
 
 // STEP 4: Encode & Transmit
 // - Encode diagnostics to Protobuf
 // - Send UDP broadcast (192.168.0.255:7)
 
 // STEP 5: Wait
 osDelay(5000); // 5 seconds
} 
 Error Handling Strategy 
 Polling Error States 
 if (poll_result == RESULT_ERR_UNIMPLEMENTED) {
 sensor.state = SENSOR_IDLE;
 sensor.error_code = COMMUNICATION_FAILURE;

} else if (poll_result == RESULT_ERR_COMMS) {
 sensor.state = SENSOR_ERROR;
 sensor.error_code = COMMUNICATION_FAILURE;

} else if (poll_result == RESULT_OK) {
 if (validate_sensor_data(value) == RESULT_OK) {
 sensor.state = SENSOR_OPERATING;
 sensor.error_code = NO_ERROR;
 } else {
 sensor.state = SENSOR_ERROR;
 sensor.error_code = INVALID_DATA;
 }
} 
 Sensor Status Codes 
 Code Meaning SENSOR_IDLE Not connected or not implemented SENSOR_OPERATING Normal operation, valid data SENSOR_ERROR Communication failure or invalid data 
 Initialization Sequence 
 Phase 1: Hardware Setup 
 1. MPU/Cache configuration
2. HAL initialization
3. System clock → 480 MHz
4. RTOS kernel init
5. GPIO initialization
6. Timer initialization (TIM1) 
 Phase 2: Communication Setup 
 1. UART initialization (115200 baud)
2. Logging system init
3. Ethernet PHY init (LAN8742)
4. MAC address filtering
5. ARP table setup 
 Phase 3: Application Setup 
 1. Packet dispatcher registration
2. Sensor initialization
3. UDP queue creation
4. UDP callback registration 
 Phase 4: Main Loop 
 1. LED initialization
2. Sensor polling starts
3. Continuous 5-second cycles

Configuration
Compile-time parameters, runtime configuration, sensor calibration setup, network addressing, UDP ports, performance tuning options 
 UDP Configuration 
 // In src/sensor_board/main.c
#define SENSOR_UDP_DEST_PORT 7
uint8_t dest_ip[4] = {192, 168, 0, 255}; // Broadcast address 
 Main Loop Timing 
 // In src/sensor_board/main.c
#define MAIN_TASK_DELAY_MS 5000 // 5 seconds between updates 
 Heap Management 
 // Critical heap threshold
#define CRITICAL_HEAP_THRESHOLD 8192 // 8 KB minimum 
 Task Configuration 
 const osThreadAttr_t mainTask_attributes = {
 .name = "mainTask",
 .stack_size = 1024 * 8, // 8 KB stack
 .priority = (osPriority_t)osPriorityNormal,
}; 
 Runtime Configuration 
 Changing Sensor Poll Interval 
 // Current: 5 seconds
#define MAIN_TASK_DELAY_MS 5000

// Change to 1 second
#define MAIN_TASK_DELAY_MS 1000

// Change to 10 seconds
#define MAIN_TASK_DELAY_MS 10000 
 Enabling/Disabling Sensors 
 // Current: skip all sensor polling during development
const bool skip_sensor_polling = true;

// To ENABLE actual polling:
const bool skip_sensor_polling = false;

// To SKIP (for testing without hardware):
const bool skip_sensor_polling = true; 
 Adjusting Heap Threshold 
 // Current: 8 KB critical
if (free_heap < 8192) {
 LOGE(TAG, "CRITICAL: Low heap detected! Free: %lu bytes", free_heap);
} 
 Sensor Calibration Configuration 
 pH Sensor Calibration 
 // Set reference voltage (typically 3.3V or 5.0V)
ph_sensor_init(&ph_sensor, 3.3f); // 3.3V reference

// Update calibration (after two-point calibration)
ph_sensor.calibration.offset = 0.0f; // Adjust after pH 7.0 test
ph_sensor.calibration.slope = 3.5f; // Adjust after second pH test 
 Load Cell Calibration 
 // After tare (no load):
load_cell_data[0].tare_offset_counts = adc_reading_no_load;

// After known weight measurement:
// scale = (force_newtons) / (adc_reading - tare_offset)
load_cell_data[0].scale_newtons_per_count = scale_factor;
load_cell_data[0].is_calibrated = true; 
 Network Configuration 
 Changing Broadcast Address 
 //To be implemented 
 Changing UDP Port 
 //To be implemented

GNSS
Global positioning module with NMEA 0183 protocol support. Contains data structures, initialization code, validation functions, and UART configuration for the GY-NEO6MV2 sensor. 
 Hardware Specifications 
 Parameter Value Model GY-NEO6MV2 (NEO-6M) Interface UART (TTL serial) Baud Rate 9600 bps Protocol NMEA 0183 Update Rate 1 Hz (configurable) 
 GPS Fix Quality Types 
 typedef enum {
 GPS_NO_FIX = 0, // No GPS fix available
 GPS_GPS_FIX = 1, // Standard GPS fix
 GPS_DGPS_FIX = 2, // Differential GPS fix
 GPS_PPS_FIX = 3, // PPS (Pulse Per Second) fix
 GPS_RTK_FIX = 4, // Real-Time Kinematic fix
 GPS_RTK_FLOAT = 5 // RTK float solution
} gps_fix_quality_t; 
 Data Structure 
 typedef struct {
 // Position Data
 double latitude; // ±90 degrees (North/South)
 double longitude; // ±180 degrees (East/West)
 float altitude; // Meters above sea level
 
 // Velocity & Direction
 float speed; // Meters per second
 float heading; // 0-360 degrees (course over ground)
 
 // Accuracy Indicators
 float hdop; // Horizontal dilution of precision
 float vdop; // Vertical dilution of precision
 int32_t satellites; // Number of satellites in view
 gps_fix_quality_t fix_quality;
 
 // Timestamps
 int64_t utc_timestamp; // Unix epoch (milliseconds)
 uint32_t timestamp; // System timestamp (last reading)
 uint32_t last_timestamp; // System timestamp (previous reading)
 
 // Status
 bool is_valid; // Data validity flag
 
 // UART Parsing State
 char rx_buffer[256]; // UART receive buffer
 uint16_t rx_index; // Current buffer position
 bool sentence_ready; // Complete sentence available
} gps_data_t; 
 NMEA Sentences Supported 
 Sentence Purpose GGA Fix data (time, position, fix quality, satellite count) RMC Recommended Min. Navigation Info (position, speed, heading, date) GSA DOP and active satellites (fix type, DOP values) 
 Initialization & Usage 
 Initialize GPS 
 gps_data_t gps_data;
gps_sensor_init(&gps_data); 
 Poll GPS Data 
 result_t gps_poll_result = poll_gps_sensor(&gps_data);

if (gps_poll_result == RESULT_OK) {
 double latitude = gps_data.latitude;
 double longitude = gps_data.longitude;
 float altitude = gps_data.altitude;
 int32_t satellites = gps_data.satellites;
 float hdop = gps_data.hdop;
} 
 Validation Functions 
 // Validate latitude (-90 to +90)
result_t validate_gps_latitude(double latitude);

// Validate longitude (-180 to +180)
result_t validate_gps_longitude(double longitude);

// Validate HDOP (horizontal dilution of precision)
// Typical range: 0-50
result_t validate_gps_hdop(float hdop);

// Validate satellite count
// Typical: 0-30 satellites
result_t validate_gps_satellite_count(int32_t satellites); 
 Protobuf Message Format 
 message SensorBoardGPSInfo {
 double latitude;
 double longitude;
 float altitude;
 float speed;
 float heading;
 float hdop;
 float vdop;
 int32 satellites;
 SensorState state;
 GPSErrorCode error_code;
} 
 Error Handling 
 if (gps_poll_result == RESULT_ERR_UNIMPLEMENTED) {
 // Hardware not connected
 diagnostics.gps_sensor_1.state = SensorState_SENSOR_IDLE;
 diagnostics.gps_sensor_1.error_code = GPSErrorCode_GPS_COMMUNICATION_FAILURE;
} else if (gps_poll_result == RESULT_ERR_COMMS) {
 // Communication error (timeout/CRC)
 diagnostics.gps_sensor_1.state = SensorState_SENSOR_ERROR;
} else if (gps_poll_result == RESULT_OK) {
 // Validate data before accepting
 if (validate_gps_latitude(gps_data.latitude) == RESULT_OK) {
 diagnostics.gps_sensor_1.state = SensorState_SENSOR_OPERATING;
 }
} 
 Integration Notes 
 Configured for dual GPS redundancy capability UART buffer size: 256 bytes NMEA sentence max length: 83 characters Data published to network at main loop interval (5 seconds default) All GPS data transmitted via UDP with Protobuf encoding Temperature range: -40°C to +85°C (standard)

pH Sensor
The pH sensor provides water quality measurement critical for environmental monitoring and anomaly detection. 
 Hardware Specifications 
 Parameter Value Model DFRobot SEN0161 (Analog pH meter) Interface Analog ADC Reference Voltage 3.3V or 5.0V (configurable) Output Range 0-5V analog Measurement Range 0-14 pH units Accuracy ±0.1 pH @ 25°C Sample Rate Configurable (40 samples for averaging) 
 Calibration Model 
 The sensor uses linear voltage-to-pH conversion: 
 pH = (Voltage / Reference_Voltage) × Slope + Offset 
 Default Parameters for SEN0161 @ 25°C: 
 Slope : 3.5 Offset : Variable (user calibration) 
 Data Structure 
 typedef struct {
 // Raw ADC Reading
 uint16_t raw_value; // Raw ADC value
 
 // Calculated Values
 float voltage; // Converted voltage (0-5V)
 float ph_value; // Calculated pH (0-14)
 float reference_voltage; // ADC reference (typically 3.3V or 5.0V)
 
 // Calibration Parameters
 ph_calibration_t calibration; // { offset: float, slope: float }
 
 // Averaging Buffer (Noise Filtering)
 uint16_t sample_buffer[40]; // Last 40 samples
 uint8_t sample_index; // Current position in buffer
 uint8_t samples_collected; // Total samples collected (0-40)
} ph_sensor_t; 
 Initialization & Usage 
 Initialize pH Sensor 
 ph_sensor_t ph_sensor;
ph_sensor_init(&ph_sensor, 3.3f); // 3.3V reference voltage 
 Poll pH Sensor 
 result_t ph_result = poll_ph_sensor(&ph_sensor);

if (ph_result == RESULT_OK) {
 float ph_value = ph_sensor.ph_value;
 float voltage = ph_sensor.voltage;
} 
 Manual Sample Addition 
 // For manual sampling at regular intervals
uint16_t adc_reading = 2048; // Example ADC value
ph_sensor_add_sample(&ph_sensor, adc_reading); 
 Validation 
 result_t validate_ph_value(float ph_value);
// Returns RESULT_OK if 0 <= ph_value <= 14
// Returns RESULT_ERR_INVALID_DATA otherwise 
 Sample Averaging Strategy 
 Parameter Value Sample Buffer Size 40 samples Method Circular buffer moving average Purpose Noise filtering and stable readings Typical Update Latency 40ms-800ms 
 Averaging Algorithm 
 1. ADC sample added to circular buffer
2. All 40 samples averaged together
3. Averaged value converted to voltage
4. Voltage converted to pH via calibration 
 Two-Point Calibration Procedure 
 Step 1: Neutral Point (pH 7.0) 
 1. Immerse electrode in pH 7.0 buffer solution
2. Wait for stable reading (~2 minutes)
3. Record voltage: V_neutral
4. Calculate offset adjustment 
 Step 2: Slope Calibration (pH 4.0 or 10.0) 
 1. Immerse electrode in second known pH solution
2. Wait for stable reading
3. Record voltage: V_reference
4. Calculate slope from two points:
 slope = (pH_reference - 7.0) / (V_reference - V_neutral) 
 Protobuf Message Format 
 message SensorBoardPHInfo {
 float ph_value;
 float voltage;
 SensorState state;
 PHErrorCode error_code;
}

enum PHErrorCode {
 PH_NO_ERROR = 0;
 PH_COMMUNICATION_FAILURE = 1;
 PH_INVALID_DATA = 2;
} 
 Error Handling 
 if (ph_result == RESULT_ERR_UNIMPLEMENTED) {
 // Hardware not connected
 diagnostics.ph_sensor.state = SensorState_SENSOR_IDLE;
 diagnostics.ph_sensor.error_code = PHErrorCode_PH_COMMUNICATION_FAILURE;
} else if (ph_result == RESULT_OK) {
 if (validate_ph_value(ph_sensor.ph_value) == RESULT_OK) {
 diagnostics.ph_sensor.state = SensorState_SENSOR_OPERATING;
 diagnostics.ph_sensor.error_code = PHErrorCode_PH_NO_ERROR;
 } else {
 // Invalid data from sensor (out of 0-14 range)
 diagnostics.ph_sensor.state = SensorState_SENSOR_ERROR;
 diagnostics.ph_sensor.error_code = PHErrorCode_PH_INVALID_DATA;
 }
} 
 Integration Notes 
 Single sensor instance in main application Updates transmitted to network at main loop interval (5 seconds default) Temperature compensation not currently implemented (assumes ~25°C) Sample averaging reduces noise but introduces ~40ms latency per update Electrode response time: ~100-300ms depending on pH change magnitude

IMU
The Inertial Measurement Unit (IMU) provides three-axis acceleration, angular velocity, and magnetic field measurements for attitude determination and motion analysis. 
 Communication Interfaces 
 Accelerometer : I2C or SPI Gyroscope : I2C or SPI Magnetometer : I2C or SPI Update Rate : Typically 1-100+ Hz (configurable) 
 Data Structure 
 typedef struct {
 // Acceleration (m/s² or g-units)
 float accel[3]; // [X, Y, Z] acceleration
 
 // Angular Velocity (rad/s or °/s)
 float gyro[3]; // [X, Y, Z] rotation rate
 
 // Magnetic Field (Gauss or µT)
 float mag[3]; // [X, Y, Z] magnetic field
 
 // Timestamps
 uint32_t timestamp; // Current reading timestamp
 uint32_t last_timestamp; // Previous reading timestamp
} imu_data_t; 
 Initialization & Usage 
 Initialize IMU 
 imu_data_t imu_data;
imu_sensor_init(&imu_data); 
 Poll IMU Data 
 result_t imu_result = poll_imu_sensor(&imu_data);

if (imu_result == RESULT_OK) {
 // Acceleration
 float accel_x = imu_data.accel[0];
 float accel_y = imu_data.accel[1];
 float accel_z = imu_data.accel[2];
 
 // Angular velocity
 float gyro_x = imu_data.gyro[0];
 float gyro_y = imu_data.gyro[1];
 float gyro_z = imu_data.gyro[2];
 
 // Magnetic field
 float mag_x = imu_data.mag[0];
 float mag_y = imu_data.mag[1];
 float mag_z = imu_data.mag[2];
} 
 Advanced Functions 
 Update with Raw Values 
 result_t imu_sensor_update(
 imu_data_t *imu,
 float ax, float ay, float az, // Accelerometer values
 float gx, float gy, float gz, // Gyroscope values
 float mx, float my, float mz, // Magnetometer values
 uint32_t timestamp
); 
 Calculate Acceleration Magnitude 
 float acceleration_magnitude = imu_get_acceleration_magnitude(&imu_data);
// Useful for impact detection and free-fall detection 
 Thread-Safe Data Reading 
 imu_data_t imu_copy;
imu_sensor_read(&imu_data, &imu_copy);
// Use imu_copy in another thread without locking 
 Typical Sensor Ranges 
 Measurement Typical Range Units Acceleration ±16 g Angular Velocity ±2000 °/s Magnetic Field ±4800 µT 
 Conversion Reference 
 From To Factor g m/s² × 9.81 °/s rad/s × π/180 Gauss µT × 100 
 Validation Functions 
 // Validate single accelerometer value
// Typical range: -50 to +50 m/s2 
result_t validate_accelerometer_value(float accel_value);

// Validate all three acceleration axes
result_t validate_imu_data(
 float accel_x,
 float accel_y,
 float accel_z
); 
 Protobuf Message Format 
 message SensorBoardIMUInfo {
 float accel_x;
 float accel_y;
 float accel_z;
 float gyro_x;
 float gyro_y;
 float gyro_z;
 SensorState state;
} 
 Common Applications 
 Impact Detection 
 float mag = imu_get_acceleration_magnitude(&imu_data);
if (mag > IMPACT_THRESHOLD) {
 // High acceleration detected
} 
 Tilt Detection 
 // Calculate tilt angle from acceleration
float tilt_angle = atan2(imu_data.accel[0], imu_data.accel[2]); 
 Motion Classification 
 // Static vs dynamic based on gyro magnitude
float gyro_mag = sqrt(gyro_x*gyro_x + gyro_y*gyro_y + gyro_z*gyro_z); 
 Integration Notes 
 Single IMU instance with 3-axis sensors (dual planned) All three axes transmitted as independent fields Acceleration magnitude available for impact detection Timestamp tracking enables dead reckoning applications Typical IMU update rate: 10-100 Hz Filter algorithms can be applied to raw data for smoothing

Load Cell
Load cells measure force/weight to detect object presence, evaluate structural loading, or monitor mechanical stress. The system supports dual load cell configuration. 
 Hardware Specifications 
 Parameter Value Sensor Count 2 (independent) Interface Analog ADC Measurement Force (Newtons) / Mass (grams) Update Rate Configurable 
 Data Structure 
 typedef struct {
 // Raw Reading
 int32_t raw_counts; // ADC value from sensor
 
 // Converted Measurements
 float force_newtons; // Force in Newtons (N)
 float mass_grams; // Equivalent mass in grams (g)
 
 // Calibration Parameters
 float scale_newtons_per_count; // Conversion factor (N/count)
 int32_t tare_offset_counts; // Zero-load ADC offset
 
 // Status
 bool is_calibrated; // Calibration valid flag
} load_cell_data_t; 
 Initialization 
 Initialize Load Cells 
 load_cell_data_t load_cell_data[2]; // Support 2 sensors

for (size_t i = 0; i < 2; i++) {
 load_cell_sensor_init(&load_cell_data[i]);
} 
 Poll Load Cell Sensor 
 result_t lc_result = poll_load_cell_sensor(&load_cell_data[0]);

if (lc_result == RESULT_OK) {
 float force = load_cell_data[0].force_newtons;
 float mass = load_cell_data[0].mass_grams;
 int32_t raw = load_cell_data[0].raw_counts;
} 
 Data Access Functions 
 // Get force in Newtons
result_t load_cell_get_force_newtons(
 const load_cell_data_t *data,
 float *force_newtons
);

// Get mass in grams (estimated)
result_t load_cell_get_mass_grams(
 const load_cell_data_t *data,
 float *mass_grams
);

// Get raw ADC counts
result_t load_cell_get_raw_counts(
 const load_cell_data_t *data,
 int32_t *raw_counts
);

// Get calibration parameters
result_t load_cell_get_calibration(
 const load_cell_data_t *data,
 float *scale_newtons_per_count,
 int32_t *tare_offset_counts
);

// Verify sensor validity
result_t load_cell_sensor_is_valid(
 const load_cell_data_t *data,
 bool *is_valid
); 
 Calibration Procedure 
 Two-Step Calibration 
 Step 1: Tare (Zero Load) 
 1. Remove all load from sensor
2. Measure ADC value: ADC_zero
3. Set tare_offset_counts = ADC_zero 
 Step 2: Span (Known Weight) 
 1. Place known weight on sensor
2. Measure ADC value: ADC_loaded
3. Know reference force: F_ref (Newtons)

4. Calculate scale:
 scale = (F_ref - 0.0) / (ADC_loaded - ADC_zero)
 
5. Set scale_newtons_per_count = scale 
 Measurement Formulas 
 // Raw force calculation
Force = (raw_counts - tare_offset_counts) × scale_newtons_per_count

// Mass conversion (approximate)
Mass_grams = (Force_newtons / 9.81) × 1000
 ≈ Force_newtons × 102.04 
 Dual Sensor Management 
 Configuration Example 
 // Initialize both sensors
for (size_t i = 0; i < 2; i++) {
 load_cell_sensor_init(&load_cell_data[i]);
}

// Poll both in sequence
poll_load_cell_sensor(&load_cell_data[0]);
poll_load_cell_sensor(&load_cell_data[1]);

// Access by index
float load_0 = load_cell_data[0].force_newtons;
float load_1 = load_cell_data[1].force_newtons; 
 Protobuf Message Format 
 message SensorBoardLoadCellInfo {
 uint32 sensor_index; // 0 or 1
 float force_newtons;
 float mass_grams;
 SensorState state;
 LoadCellErrorCode error_code;
} 
 Unit Conversions 
 From To Factor Newtons kilograms-force (kgf) ÷ 9.81 Newtons pounds-force (lbf) ÷ 4.448 grams kilograms ÷ 1000 
 Manual Unit Conversion Example 
 // Convert to pounds-force
float force_lbf = load_cell_data[0].force_newtons / 4.448f;

// Convert to kilograms
float mass_kg = load_cell_data[0].mass_grams / 1000.0f; 
 Typical Specifications 
 Load Cell Type Max Load Accuracy Strain gauge (±50N) 50N ±0.1% Load cell (±100N) 100N ±0.05% Heavy duty (±1000N) 1000N ±0.1% 
 Integration Notes 
 Supports up to 2 independent load cell sensors Hardware-specific ADC implementation Force conversion via linear scaling model Tare offset corrects for sensor mechanical zero Real-time monitoring of structural loads Each sensor maintains separate calibration Independent error reporting per sensor

Pressure Sensor
Pressure sensors measure fluid/gas pressure for robotic gripper force feedback and control, depth sensing, altitude measurement, or system pressure monitoring. The system supports dual pressure sensor configuration for dual-pad gripper control with load distribution feedback. 
 Hardware Specifications 
 Parameter Value Sensor Count 2 (independent) Interface Analog ADC or I2C Measurement Range Variable (typically 0-300 kPa) Update Rate Configurable 
 Data Structure 
 typedef struct {
 float pressure_kpa; // Pressure in kilopascals (kPa)
 float temperature_c; // Temperature in Celsius (°C)
 float voltage; // Sensor output voltage
 bool is_calibrated; // Calibration status flag
} pressure_sensor_data_t; 
 Initialization 
 Initialize Pressure Sensors 
 pressure_sensor_data_t pressure_data[2]; // Support 2 sensors

for (size_t i = 0; i < 2; i++) {
 pressure_sensor_init(&pressure_data[i]);
} 
 Poll Pressure Sensor 
 result_t ps_result = poll_pressure_sensor(&pressure_data[0]);

if (ps_result == RESULT_OK) {
 float pressure_kpa = pressure_data[0].pressure_kpa;
 float temperature_c = pressure_data[0].temperature_c;
} 
 Data Access Functions 
 // Get pressure in kilopascals
result_t pressure_sensor_get_pressure_kpa(
 const pressure_sensor_data_t *data,
 float *pressure_kpa
);

// Get temperature in Celsius
result_t pressure_sensor_get_temperature_c(
 const pressure_sensor_data_t *data,
 float *temperature_c
);

// Get raw sensor voltage
result_t pressure_sensor_get_voltage(
 const pressure_sensor_data_t *data,
 float *voltage
);

// Verify sensor validity
result_t pressure_sensor_is_valid(
 const pressure_sensor_data_t *data,
 bool *is_valid
); 
 Pressure Unit Conversions 
 Function-Based Conversions 
 // Convert pressure from bar to psi
result_t bar_to_psi(float bar, float *psi);

// Convert pressure from psi to bar
result_t psi_to_bar(float psi, float *bar); 
 Conversion Table 
 From To Multiply By bar kPa 100 psi kPa 6.895 atm kPa 101.325 kPa bar 0.01 kPa psi 0.145 kPa atm 0.00987 
 Examples 
 // 100 kPa = 1 bar
float kpa = 100.0f;
float bar = kpa * 0.01f; // Result: 1.0 bar

// 50 psi to bar
float psi = 50.0f;
float bar = psi / 14.504f; // Result: 3.45 bar

// Altitude from pressure (simplified)
// Altitude ≈ 44330 × (1 - (P/P0)^(1/5.255))
float altitude_m = 44330.0f * (1.0f - pow(pressure_kpa/101.325f, 1.0f/5.255f)); 
 Protobuf Message Format 
 message SensorBoardPressureInfo {
 uint32 sensor_index; // 0 or 1
 float pressure_kpa;
 float temperature_c;
 SensorState state;
 PressureErrorCode error_code;
} 
 Dual Sensor Management 
 Configuration Example 
 // Initialize both sensors
for (size_t i = 0; i < 2; i++) {
 pressure_sensor_init(&pressure_data[i]);
}

// Poll both in sequence
poll_pressure_sensor(&pressure_data[0]);
poll_pressure_sensor(&pressure_data[1]);

// Access by index
float pressure_0_kpa = pressure_data[0].pressure_kpa;
float pressure_1_kpa = pressure_data[1].pressure_kpa; 
 Temperature Compensation 
 Pressure readings often need temperature compensation for accuracy: 
 // Simplified temperature compensation
float compensated_pressure = pressure_data[0].pressure_kpa * 
 (reference_temperature + 273.15f) / 
 (pressure_data[0].temperature_c + 273.15f); 
 Applications 
 Robotic Gripper Control (Primary Use Case) 
 // Gripper force feedback for adaptive grip strength
// Pressure reading controls servo/motor PWM to regulate grip force

#define GRIPPER_MIN_PRESSURE_KPA 20.0f // Minimum safe grip
#define GRIPPER_MAX_PRESSURE_KPA 150.0f // Maximum allowed grip
#define GRIPPER_TARGET_PRESSURE_KPA 80.0f // Desired grip force

// PID controller for gripper force regulation
typedef struct {
 float kp, ki, kd; // PID coefficients
 float integral_error;
 float previous_error;
} gripper_pid_t;

// Adjust servo PWM based on pressure feedback
void adjust_gripper_force(float current_pressure_kpa, gripper_pid_t *pid) {
 float error = GRIPPER_TARGET_PRESSURE_KPA - current_pressure_kpa;
 
 pid->integral_error += error;
 float derivative_error = error - pid->previous_error;
 
 float pid_output = (pid->kp * error) + 
 (pid->ki * pid->integral_error) + 
 (pid->kd * derivative_error);
 
 // Clamp servo PWM to valid range
 uint16_t servo_pwm = (uint16_t)(GRIPPER_NEUTRAL_PWM + pid_output);
 servo_pwm = (servo_pwm < GRIPPER_MIN_PWM) ? GRIPPER_MIN_PWM : servo_pwm;
 servo_pwm = (servo_pwm > GRIPPER_MAX_PWM) ? GRIPPER_MAX_PWM : servo_pwm;
 
 set_gripper_pwm(servo_pwm);
 pid->previous_error = error;
} 
 Gripper Control Features: 
 Grip force feedback for object handling Object presence detection (pressure spike threshold) Adaptive compliance for varying object sizes/materials Dual sensors support load sharing across gripper pads 
 Implemented but Not Primary 
 Depth Sensing (Water) 
 // Pressure to depth in water
// P = ρ × g × h
// where ρ = 1025 kg/m³ (seawater), g = 9.81 m/s²
float depth_meters = (pressure_kpa - atmospheric_pressure_kpa) / 10.0f; 
 Altitude Sensing (Air) 
 // Barometric formula (simplified)
float altitude_m = 44330.0f * (1.0f - pow(pressure_kpa/101.325f, 1.0f/5.255f)); 
 System Pressure Monitoring 
 if (pressure_kpa > PRESSURE_WARNING_THRESHOLD) {
 // High pressure detected - safety alert
} 
 Common Pressure Sensor Ranges 
 Application Range Typical Sensor Altitude (aviation) 10-110 kPa BMP280/BMP390 Depth (diving) 0-300+ kPa Custom depth sensor System pressure 0-500+ kPa Industrial pressure transducer 
 Integration Notes 
 Primary Application: Robotic gripper force feedback and control Supports up to 2 independent pressure sensors (dual gripper pads) Temperature measurement for compensation algorithms Hardware-specific ADC or I2C implementation Pressure-voltage conversion implemented internally Real-time depth/altitude sensing capability PID control loop integration for adaptive grip force Each sensor maintains independent calibration Temperature tracking for accuracy improvements Slip detection via pressure variance analysis

Testing
Test organization, validation functions, Unity testing framework usage, manual hardware testing checklists and debugging/troubleshooting guide. 
 Test Organization 
 test/sensor_board/
├── test_gps_sensor/
│ ├── NMEA parsing verification
│ ├── Coordinate validation
│ └── Fix quality enumeration tests
│
├── test_imu_sensor/
│ ├── 3-axis data structure tests
│ ├── Acceleration magnitude calculation
│ └── Timestamp tracking validation
│
├── test_load_sensor/
│ ├── Force calculation (tare/scale)
│ ├── Mass conversion (g/kg/lbf)
│ ├── Dual sensor independence
│ └── Calibration parameter storage
│
├── test_ph_sensor/
│ ├── ADC to voltage conversion
│ ├── pH value calculation
│ ├── Sample averaging (40-sample buffer)
│ ├── Calibration offset/slope
│ └── Edge cases (pH 0, 14)
│
├── test_pressure_sensor/
│ ├── Pressure reading validation
│ ├── Temperature compensation
│ ├── Unit conversions (bar/psi/kPa)
│ └── Dual sensor independence
│
└── test_sensor_basics/
 ├── Conversion functions
 ├── Validation functions
 ├── Range checking
 └── Boundary conditions 
 Validation Functions 
 GPS Validation 
 result_t validate_gps_latitude(double latitude);
// Valid range: -90.0 to +90.0 degrees

result_t validate_gps_longitude(double longitude);
// Valid range: -180.0 to +180.0 degrees

result_t validate_gps_hdop(float hdop);
// Typical range: 0.0 to 50.0

result_t validate_gps_satellite_count(int32_t satellites);
// Typical range: 0 to 30 satellites 
 pH Validation 
 result_t validate_ph_value(float ph_value);
// Valid range: 0.0 to 14.0 
 IMU Validation 
 result_t validate_accelerometer_value(float accel_value);
// Typical range: -50.0 to +50.0 m/s²

result_t validate_imu_data(float accel_x, float accel_y, float accel_z); 
 Unit Conversion Tests(extra stuff) 
 result_t celsius_to_fahrenheit(float celsius, float *fahrenheit);
result_t fahrenheit_to_celsius(float fahrenheit, float *celsius);
result_t bar_to_psi(float bar, float *psi);
result_t psi_to_bar(float psi, float *bar); 
 Test Framework 
 Testing Technology 
 Framework : Unity (open-source testing framework) Build System : CMake / PlatformIO Test Type : Hosted unit tests (run on PC) Mocking : Mock ADC/UART/I2C interfaces 
 Building Tests 
 // Build all tests
pio test -e sensor_board

// Run specific test suite
pio test -e sensor_board -f test_ph_sensor 
 Debugging & Troubleshooting 
 Issue Cause Solution Sensor IDLE Not connected Check UART/I2C/SPI wiring Sensor ERROR Communication failure Verify baud rates, addresses Invalid data Out of range Check calibration parameters Low heap warning Memory leak Review packet encoder

Reference
Checkout the embedded simplified from ERC 
 Source Code References 
 If you made it till here, you a true G. Also, this was rather useful, check this out... ERC Embedded Simplified Official 
 Main Application 
 File Purpose src/sensor_board/main.c Main entry point and sensor loop 
 Sensor Drivers 
 Sensor Header Source GPS components/sensor_board/gps/gps_sensor.h gps_sensor.c IMU components/sensor_board/imu/imu_sensor.h imu_sensor.c pH components/sensor_board/ph/ph_sensor.h ph_sensor.c Load Cell components/sensor_board/load_cell/load_cell_sensor.h load_cell_sensor.c Pressure components/sensor_board/pressure/pressure_sensor.h pressure_sensor.c Utilities components/sensor_board/sensor_basics/sensor_basics.h sensor_basics.c 
 Protobuf Definitions 
 For detailed protobuf message format documentation, see: Sensor Board Protobuf 
 ERC-Protobufs/components/sensor_board/
├── diagnostics.proto - Board-level diagnostics and health status
├── sensor.proto - Aggregated sensor state message
├── gps_sensor.proto - GNSS positioning data
├── imu_sensor.proto - Inertial measurement (acceleration, gyro, mag)
├── ph_sensor.proto - Water quality pH measurement
├── load_cell.proto - Force measurement (gripper control)
└── pressure_sensor.proto - Pressure measurement (gripper control) 
 Build Configuration 
 File Purpose platformio.ini Build configuration for all boards .mxproject STM32 CubeMX configuration firmware.ioc CubeMX IOC file (device config) 
 Test References 
 Test Suites 
 test/sensor_board/
├── test_gps_sensor/
├── test_imu_sensor/
├── test_load_sensor/
├── test_ph_sensor/
├── test_pressure_sensor/
└── test_sensor_basics/ 
 Running Tests 
 // Build all tests
pio test -e sensor_board

// Run with verbose output
pio test -e sensor_board -v

// Build only (no run)
pio test -e sensor_board --no-run 
 Hardware References 
 Microcontroller 
 STM32H753ZI - ARM Cortex-M7, 480 MHz, 1 MB Flash Datasheet : ST Microelectronics STM32H7 reference 
 Ethernet 
 LAN8742 - Ethernet PHY Interface : RMII (Reduced Media Independent Interface) Link Speed : 10/100 Mbps auto-negotiation 
 Sensors 
 Sensor Model Protocol Note GPS GY-NEO6MV2 (NEO-6M) UART 9600 Default NMEA config IMU Reference design TBD I2C/SPI Dual IMU planned pH DFRobot SEN0161 ADC Analog 40-sample averaging Load Cell Application specific ADC Dual cells (×2) Pressure Application specific ADC/I2C Dual sensors (×2) 
 Development Workflow 
 Building Firmware 
 // Build for sensor_board
pio run -e sensor_board

// Upload to board
pio run -e sensor_board --target upload

// Monitor serial output
pio device monitor -b 115200 -p COM4 
 Development Cycle 
 // 1. Edit source code
// 2. Build
pio run -e sensor_board

// 3. Upload
pio run -e sensor_board --target upload

// 4. Monitor
pio device monitor

// 5. Run tests
pio test -e sensor_board 
 Useful Commands 
 PlatformIO CLI 
 // List available boards
pio boards

// Show board info
pio boards nucleo_h753zi

// Clean build
pio run -e sensor_board --target clean

// Full rebuild
pio run -e sensor_board --target clean --target upload 
 Troubleshooting Guide 
 Serial Monitor No Output 
 Check USB connection Verify COM port in platformio.ini Check baud rate (115200) Verify UART initialization succeeded 
 Sensor Shows IDLE 
 Check physical connection (UART/I2C/SPI) Verify baud rate (for UART sensors) Check pull-up resistors (for I2C) Verify device address (for I2C/SPI) 
 Network Packets Not Received 
 Check IP address configuration Verify MAC address filtering Check firewall settings Verify UDP port 7 not blocked 
 Low Heap Warning 
 Check for memory leaks in sensor drivers Reduce buffer sizes Verify UDP queue sizes Check for recursive allocations 
 Quick Reference Checklist 
 Before Deployment 
 All sensors connected and responding Network IP/MAC configured correctly Calibration parameters set for pH/load cells Serial monitor showing sensor data Heap usage monitored (>8KB free) UDP packets reaching destination Protobuf encoding verified 
 Monitoring in Production 
 Check sensor status codes Monitor heap usage trend Verify data ranges match expectations Track error rates per sensor Review network packet statistics 
 
 Hope you had fun☮️ 
 END OF DOCUMENTATION FOR SESOR BOARD ☮️ 
 Last Updated: April 14, 2026

Debugging Board
Lil gameboy doodad

Overview
The debugging board is a dedicated auxiliary system whose only job is to make the rest of the robot less painful to work with. 
 It is not part of the rover’s core functionality. 
 Purpose 
 At a high level, the debugging board serves roles: 
 Visibility 
 Provide real-time insight into system state: 
 logs status indicators network activity subsystem health 
 Instead of digging through serial output on multiple MCUs or adding temporary debug code everywhere, this board aggregates and presents useful information. 
 Control / Interaction 
 Todo :D 
 Isolation of debugging concerns 
 Todo :D 
 Physical components 
 The exact hardware may evolve, but the debugging board generally consists of: 
 Ethernet interface 
 Connects to the system network (switch / internal bus) Receives and sends packets (including protobuf-based messages) Acts as a bridge between the debugging interface and the rest of the robot 
 Display 
 Shows system state, logs, or selected information It is a ILI9341 SPI Display 
 Used for quick, local feedback without needing a laptop. 
 Input interface (buttons / panel) 
 Physical buttons or switches Used to: trigger actions navigate menus send commands

Display - ILI9341 Hardware Configuratoin
The debugging board incorporates a graphical display based on the ILI9341 controller. This display serves as the primary local interface for presenting system state, diagnostics, and user feedback. 
 The ILI9341 is a widely used TFT LCD controller that integrates display driving logic, internal GRAM (Graphics RAM), and a command-based interface over serial or parallel buses. In this system, it is used in SPI mode , which aligns with the board’s pin constraints and simplifies integration with the MCU. 
 Functional Role in the System 
 Within the debugging board, the display is responsible for: 
 Rendering system status (connectivity, subsystem health, etc.) Displaying structured debugging information Providing immediate visual feedback to user input (button interactions) Supporting simple UI constructs (menus, indicators, overlays) 
 The display is not intended for high-throughput graphics or complex rendering. Its role is informational and interactive , not graphical-intensive. 
 Features of the ILI9341 
 The ILI9341 controller provides a set of features well suited for embedded applications. 
 Resolution and Color Depth 
 Resolution: 240 × 320 pixels Color depth: 16-bit RGB (RGB565) 
 This provides sufficient resolution for: 
 text rendering simple UI layouts basic graphical elements (icons, shapes) 
 Internal GRAM (Frame Buffer) 
 The controller includes internal Graphics RAM (GRAM) , which stores pixel data. 
 The MCU does not need to maintain a full framebuffer Pixel data is written directly to the display over SPI The display retains the image until overwritten 
 This significantly reduces RAM requirements on the MCU, which is critical in embedded systems. 
 Command-Based Interface 
 The display is controlled through a command/data protocol: 
 Commands configure behavior (e.g., orientation, pixel format) Data writes update pixel values in GRAM 
 Typical operations include: 
 setting an address window writing pixel data issuing initialization sequences 
 Display Orientation and Addressing 
 The controller supports: 
 configurable screen rotation (portrait / landscape) programmable address windows 
 This allows: 
 flexible UI layout efficient partial updates (writing only specific regions) 
 Hardware Reset and Initialization 
 The display requires: 
 a hardware reset sequence a series of configuration commands during initialization 
 These typically configure: 
 power control gamma curves pixel format memory access control 
 ILI9341 is a relatively complex and if you want to do anything with the internal library of it you need more than what can be written here. Read the official documentation 
 MCU Configuration 
 The SPI peripheral must be configured with: 
 Mode: Full-Duplex Master Data size: 8-bit First bit: MSB-first Clock polarity: Low Clock phase: 1st edge NSS: Software Baud rate prescaler: selected based on display stability 
 These settings must match the display’s timing requirements. 
 For the baud rate, you want it to be as high as possible without it being unstable. For debugging and testing, it's good practice to lower it first, get it working there (as it is a lot more stable) and then increase it again.

Display - ILI9341 Library
Purpose 
 The ili9341 library provides the low-level and mid-level drawing interface for the ILI9341-based display used on the debugging board. 
 Its role is to hide the raw command sequence and SPI transaction details of the display controller behind a set of functions for: 
 initialization display configuration pixel and region drawing primitive graphics text rendering monochrome bitmap rendering rounded rectangle rendering 
 In other words, this library is the software layer that turns the display from a peripheral into a usable rendering surface. 
 Scope of the Library 
 This library sits close to the hardware. 
 It is responsible for: 
 driving the ILI9341 controller over SPI controlling the display GPIO lines ( CS , DC , RST ) issuing the controller initialization sequence writing pixel data to the display GRAM exposing simple drawing primitives for higher-level UI code 
 It is not responsible for: 
 application UI logic layout management widget systems maintaining a full framebuffer asynchronous rendering scheduling 
 This is a direct-draw display driver and utility library, not a graphics framework. 
 High-Level Design 
 The library is structured around four layers of functionality. 
 Transport layer 
 These functions send commands and bytes over SPI: 
 ILI9341_SPI_Send() ILI9341_Write_Command() ILI9341_Write_Data() 
 Display control layer 
 These functions manage display state and configuration: 
 ILI9341_Reset() ILI9341_Set_Address() ILI9341_Set_Rotation() ILI9341_Enable() ILI9341_Init() 
 Primitive drawing layer 
 These functions draw directly to the screen: 
 single colours pixels colour bursts lines rectangles bitmaps colour arrays 
 Utility rendering layer 
 These functions build on the primitives to provide: 
 text rendering rounded-corner rendering custom monochrome corner bitmap generation 
 This layered structure is important. Most higher-level code should use the drawing primitives and utility functions, not manually emit ILI9341 commands unless there is a very specific reason. 
 Hardware Interface Definitions 
 The header defines the display connection through compile-time macros. 
 SPI instance 
 #define HSPI_INSTANCE &hspi1 
 This selects the SPI peripheral used to communicate with the display. 
 GPIO control lines 
 #define LCD_CS_PORT TFT_CS_GPIO_Port
#define LCD_CS_PIN TFT_CS_Pin

#define LCD_DC_PORT TFT_DC_GPIO_Port
#define LCD_DC_PIN TFT_DC_Pin

#define LCD_RST_PORT TFT_RESET_GPIO_Port
#define LCD_RST_PIN TFT_RESET_Pin 
 These define: 
 chip select data/command selection hardware reset 
 The library assumes these symbols are provided by the board support layer. 
 Screen dimensions 
 #define ILI9341_SCREEN_HEIGHT 240
#define ILI9341_SCREEN_WIDTH 320 
 These define the nominal physical display dimensions.. 
 Burst limit 
 #define BURST_MAX_SIZE 500 
 This controls the maximum temporary buffer size used during burst-style SPI transfers. 
 It affects: 
 solid colour fills colour array streaming bitmap rendering 
 This is a performance and stack/RAM tradeoff parameter. 
 Color Definitions 
 The header provides a set of named RGB565 color constants, for example: 
 BLACK WHITE RED GREEN BLUE YELLOW CYAN MAGENTA 
 These are convenience values for application code and drawing functions. 
 All colors are represented in 16-bit RGB565 format , which matches the configured pixel format of the display controller. 
 Initialization Sequence 
 ILI9341_Init() 
 void ILI9341_Init(void); 
 This is the main initialization routine. 
 What it does 
 It performs: 
 display enable SPI init hook hardware reset software reset a full controller configuration sequence exit from sleep mode display on initial screen rotation selection 
 Initialization sequence contents 
 The function writes a fixed command sequence configuring: 
 power control driver timing pump ratio VCOM control memory access control pixel format frame rate gamma correction sleep exit display enable 
 This is the board’s current known-good configuration for the display. 
 Why this matters 
 This sequence is not arbitrary boilerplate. It defines the electrical and visual behavior of the panel. 
 If it is modified, the maintainer must understand whether the change is: 
 controller-required panel-specific timing-related cosmetic or cargo-culted from another project 
 Basic Drawing Primitives 
 ILI9341_Draw_Colour() 
 void ILI9341_Draw_Colour(uint16_t Colour); 
 Writes one pixel’s worth of RGB565 data to the display. 
 This function assumes the correct address window is already set. 
 It is mainly an internal low-level helper. 
 ILI9341_Draw_Colour_Burst() 
 void ILI9341_Draw_Colour_Burst(uint16_t Colour, uint32_t Size); 
 Draws a repeated color value over a number of pixels. 
 Use case 
 Efficiently fill: 
 large solid regions lines screen clears 
 How it works 
 It creates a temporary burst buffer containing repeated color bytes and transmits it in chunks. 
 This is much more efficient than sending each pixel individually. 
 Importance 
 This function is central to the performance of: 
 full screen fills rectangle fills line drawing 
 ILI9341_Draw_Colour_Array() 
 void ILI9341_Draw_Colour_Array(const uint16_t *Colour, uint32_t PixelCount); 
 Draws an array of RGB565 pixel values. 
 Use case 
 Use this when the caller already has pixel data prepared, for example: 
 image rendering precomputed graphics generated color buffers 
 Important implementation detail 
 The function converts each uint16_t color into big-endian byte order before sending. 
 This is correct for SPI transmission to the display controller. 
 ILI9341_Draw_Pixel() 
 void ILI9341_Draw_Pixel(uint16_t X, uint16_t Y, uint16_t Colour); 
 Draws one pixel at a specific coordinate. 
 Behavior 
 It: 
 bounds checks the coordinate manually sets X address manually sets Y address issues memory write writes one pixel color 
 Performance note 
 This is a very slow operation compared to region-based drawing because it reissues addressing commands for every pixel. 
 It is suitable for: 
 sparse pixel updates debugging very small shapes 
 It is not suitable for rendering larger regions. 
 ILI9341_Fill_Screen() 
 void ILI9341_Fill_Screen(uint16_t Colour); 
 Fills the whole display with one color. 
 Behavior 
 It sets the address window to the whole screen and then sends a repeated-color burst. 
 Text Rendering 
 ILI9341_WriteString() 
 void ILI9341_WriteString(uint16_t x, uint16_t y, const char *str,
 ILI9341_FontDef font, uint16_t color,
 uint16_t bgcolor); 
 Renders a null-terminated string using the specified font and foreground/background colors. 
 Behavior 
 iterates through each character wraps to the next line if the current X position exceeds screen width stops if the next line would exceed screen height 
 Internal helper 
 This uses the internal function: 
 static void ILI9341_WriteChar(...) 
 which renders one character pixel-by-pixel using the font bitmap. 
 Bitmap Rendering 
 ILI9341_Draw_Bitmap() 
 void ILI9341_Draw_Bitmap(uint16_t x, uint16_t y,
 uint16_t w, uint16_t h,
 const uint8_t *bitmap,
 uint16_t Color, uint16_t BgColor); 
 Draws a 1-bit-per-pixel bitmap into a rectangular region. 
 Expected bitmap format 
 The input bitmap is interpreted as packed monochrome data: 
 1 bit per pixel row-major MSB-first within each byte 
 Rendering behavior 
 For each bit: 
 set bit -> draw Color clear bit -> draw BgColor 
 Use case 
 This is useful for: 
 icons glyph-like shapes masks rounded corner patterns 
 It is not for full-color image rendering. 
 R³: Rounded Rectangle Rendering 
 The library includes support for rounded rectangle outlines using generated monochrome corner bitmaps. 
 This is more advanced than the rest of the primitive API and deserves separate explanation. 
 Why? 
 The reasons why the R³ system is highly important - if not necessary - are plenty and extensive. That's why I compiled a pastebin that includes all reasons . Feel free to read it even though I believe it is pretty self explanatory 
 Concept 
 A rounded rectangle is rendered by: 
 generating a 1bpp bitmap for one rounded corner rotating that bitmap to obtain all four corners drawing the four corner bitmaps drawing straight rectangle segments between them 
 This is a practical method for an SPI-driven display because it avoids expensive per-pixel circle calculations at draw time for every corner. 
 Internal helpers 
 The implementation includes internal static helpers: 
 ILI9341_Get_Rounded_Corner_Bitmap() bitmap_rotate_90_cw_1bpp() ILI9341_Build_All_Rounded_Corners() ILI9341_Draw_Rectangle_Custom_Corner() 
 These are not part of the public API, but they are important for maintainers to understand. 
 ILI9341_Draw_Rectangle_Rounded_Corner() 
 result_t ILI9341_Draw_Rectangle_Rounded_Corner(
 uint16_t X, uint16_t Y, uint16_t Width, uint16_t Height,
 uint8_t thickness, uint8_t radius,
 uint8_t *corner_buffer, size_t corner_buffer_size,
 uint16_t Colour, uint16_t Bg_Colour); 
 This is the main public rounded rectangle API currently implemented with explicit caller-provided corner buffer storage. 
 Why caller-provided memory is used 
 The function requires the caller to provide a temporary buffer for the generated corner bitmaps. 
 This avoids hidden dynamic allocation and gives the caller control over memory use. 
 Buffer sizing 
 The function expects enough memory for four 1bpp bitmaps, one for each corner. 
 It computes the required size as: 
 4 * (((radius + 7) >> 3) * radius) 
 in bytes. 
 Return values 
 RESULT_OK on success RESULT_ERR_NO_MEM if the provided buffer is too small RESULT_ERR_INVALID_ARG for invalid parameters via internal helpers 
 Use case 
 This function is appropriate when the UI wants rounded bordered rectangles without a full framebuffer.

Menu Driver - Overview
Purpose 
 The menu driver is a page-based UI framework for an embedded display (ILI9341). 
 It defines: 
 how UI is structured into pages how state is stored per page how navigation works how rendering is organized 
 Architecture Position 
 [ Application Logic ] 
↓[ Menu Driver ] 
↓[ ILI9341 Driver ] 
↓[ SPI / Hardware ] 
 It does not : 
 own the main loop schedule tasks interpret input fully 
 It does : 
 define UI structure manage page lifecycle coordinate rendering 
 
 1.3 Design Model 
 Everything revolves around: 
 “A UI is a collection of pages with lifecycle and state.” 
 Each page has: 
 state init/update/render/destruct parent relationship 
 Input / System Events
 │
 ▼
 ┌─────────────────────┐
 │ menu_manager_t │
 │─────────────────────│
 │ active_page_id │
 │ pages[] │
 │ get_input() │
 └─────────┬───────────┘
 │ selects active page
 ▼
 ┌──────────────────────────────────┐
 │ Active Page │
 │──────────────────────────────────│
 │ state pointer │
 │ init() ─┐ │
 │ update() ├─ custom page │
 │ render() ┤ behavior │
 │ destruct() ┘ │
 └────────────────┬─────────────────┘
 │ reads/writes
 ▼
 ┌──────────────────┐
 │ Page State │
 │──────────────────│
 │ selection │
 │ cached values │
 │ render flags │
 │ page-local data │
 └──────────────────┘

Menu Driver - Configuration Layer
Visual Configuration 
 #define MENU_DRIVER_BACKGROUND_COLOR 0x0000
#define MENU_DRIVER_FOREGROUND_COLOR 0xFFFF 
 Black background, white foreground. 
 Layout Constraints 
 #define MENU_SIDEBAR_WIDTH 38 
 Sidebar (ribbon) width. 
 Capacity Limits 
 List Pages 
 #define MAX_LIST_ENTRIES 10
#define MAX_LIST_TITLE_LEN 24 
 Overview Pages 
 #define MENU_OVERVIEW_MAX_ENTRIES 10
#define MENU_OVERVIEW_MAX_ENTRY_TITLE_LEN 12 
 Global 
 #define MAX_PAGE_NAME_LEN 20 
 These define: 
 memory footprint UI density rendering assumptions

Menu Driver - Core Data Structures
Page State Types 
 A page state is: 
 The persistent data container that represents everything a UI page needs to function between frames. 
 Not just data. It’s: 
 memory of what the user did memory of what was rendered memory of external data (diagnostics, etc.) 
 List Page State 
 typedef struct {
 uint8_t num_entries;
 uint8_t selected_index;
 uint8_t entry_ids[MAX_LIST_ENTRIES];
 const uint8_t (*entry_icons)[MENU_DRIVER_ICON_BYTE_SIZE];
 bool first_render;
} page_list_state; 
 Responsibilities: 
 track selection map entries → page IDs hold icons manage first render optimization 
 Overview Page State 
 Todo :D 
 State Union 
 typedef union {
 page_list_state list;
 page_overview_state overview;
} menu_page_state; 
 Page Type 
 typedef enum {
 MENU_PAGE_TYPE_LIST,
 MENU_PAGE_TYPE_OVERVIEW,
} menu_page_type_t; 
 Used to interpret the union correctly. 
 Page Object 
 typedef struct {
 menu_page_state *state;
 menu_page_type_t type;
 unsigned char id;
 unsigned char parent_id;
 bool needs_render;

 char name[MAX_PAGE_NAME_LEN];

 void (*init)(menu_page_state *);
 void (*update)(menu_manager_t *);
 void (*render)(menu_manager_t *);
 void (*destruct)(menu_page_state *);
} menu_page_t; 
 This is the core abstraction . 
 Definition and Role 
 A page object represents one logical screen within the menu system. It encapsulates: 
 the data required to represent the page (via its state) the functions required to manage its lifecycle metadata used for navigation and identification 
 This abstraction allows the menu system to treat all pages uniformly, regardless of their internal implementation or purpose. 
 Important Fields 
 Render Control 
 bool needs_render; 
 This flag indicates whether the page requires re-rendering. 
 It allows the system to avoid unnecessary redraw operations, which is critical in environments where display updates are expensive. 
 The responsibility for managing this flag lies with the page implementation . 
 Lifecycle Function Pointers 
 Each page defines its own behavior through four function pointers: 
 Initialization 
 void (*init)(menu_page_state *state); 
 Responsible for preparing the page state when the page becomes active. 
 Typical responsibilities include: 
 resetting selection indices initializing flags preparing any required data structures 
 Update 
 void (*update)(struct menu_manager_t *manager); 
 Handles input processing and state updates. 
 This function is expected to: 
 read input through the manager modify internal state accordingly trigger page transitions if necessary 
 Render 
 void (*render)(struct menu_manager_t *manager); 
 Responsible for drawing the page to the display. 
 This function should: 
 read from the page state issue drawing commands via the display driver respect the needs_render flag when applicable 
 Destruction 
 void (*destruct)(menu_page_state *state); 
 Handles cleanup when the page is no longer active. 
 In embedded systems, this typically involves: 
 resetting state fields releasing logical ownership of resources 
 Dynamic memory cleanup is generally not required unless explicitly used. 
 Menu Manager 
 typedef struct {
 unsigned char active_page_id;
 const menu_page_t *pages;
 menu_input (*get_input)(void);
} menu_manager_t; 
 Responsibilities: 
 track active page provide input access hold page table 
 Does NOT: 
 validate anything own memory manage concurrency

Menu Driver - Overview Page
Introduction 
 The List Page is a navigation-oriented page type within the menu driver. It provides a structured interface for selecting between multiple entries, typically representing: 
 subpages actions system modules 
 It is the primary mechanism for user-driven navigation within the menu system. 
 Purpose 
 The list page exists to answer: 
 “Where do you want to go next?” 
 It is not responsible for displaying system state in detail. Instead, it: 
 presents a bounded set of selectable entries tracks the current selection provides visual feedback for navigation enables transitions to other pages 
 In practice, it functions as the entry point and routing layer of the UI. 
 Architectural Role 
 The list page sits at the intersection of: 
 input handling (user navigation) menu structure (page hierarchy) visual rendering (icons and labels) 
 [ Input ] → [ List Page ] → [ Page Transition ] 
 It does not consume system data (like overview pages), but rather controls flow through the interface . 
 Data Model 
 The list page is backed by the following state structure: 
 typedef struct {
 uint8_t num_entries;
 uint8_t selected_index;
 uint8_t entry_ids[MAX_LIST_ENTRIES];
 const uint8_t (*entry_icons)[MENU_DRIVER_ICON_BYTE_SIZE];
 bool first_render;
} page_list_state; 
 Entry Management 
 num_entries 
 Defines how many entries are currently active. 
 This value must not exceed MAX_LIST_ENTRIES . 
 entry_ids 
 Maps each visible entry to a logical identifier. 
 These IDs are typically used to: 
 determine which page to switch to associate actions with selections 
 entry_icons 
 Pointer to icon data associated with each entry. 
 Icons are rendered alongside entries Each icon is a fixed-size bitmap Icons are stored in flash as static data 
 Selection State 
 selected_index 
 Indicates which entry is currently selected. 
 This is the central piece of state for navigation. 
 All rendering and transitions depend on this value. 
 Render Control 
 first_render 
 Indicates whether the page is being rendered for the first time. 
 Used to: 
 trigger full initial draw avoid redundant rendering of static UI elements 
 Rendering Model 
 The list page uses a focused rendering strategy , rather than displaying all entries simultaneously. 
 Visible Entries 
 Only three entries are rendered at any time: 
 previous entry current (selected) entry next entry 
 This creates a scrolling effect without requiring full list rendering. 
 Rendering Optimization 
 The only expensive draw of the list page is the initial one which draws the selection border, all initial entries (both icons and names). 
 After that the only thing that gets redrawn are the icons and the texts. There is also heavier optimization done for minimal font redrawing by keeping track of previously rendered text widths. 
 This is critical for SPI-driven displays, where bandwidth is limited. 
 Interaction Model 
 The list page assumes an abstract input interface: 
 menu_input (*get_input)(void); 
 The page does not interpret physical inputs directly. Instead, it operates on abstract input values, allowing it to remain independent of hardware specifics. 
 Expected interactions include: 
 move selection up move selection down confirm selection 
 Relationship to Menu System 
 The list page enables hierarchical navigation through: 
 entry_ids → target page identifiers parent_id (in menu_page_t ) → upward navigation 
 This allows the menu system to behave as a tree of pages , rather than a flat structure. 
 Performance Considerations 
 The list page is designed for constrained environments: 
 partial rendering minimizes SPI usage static memory avoids allocation overhead limited visible entries reduce draw complexity