Sensor Board Protobuf

This page: Complete protobuf message definitions for the sensor_board component.

The protobuffers for the sensor_board are passed between embedded, the network, and other boards for diagnostics and data collection. This page documents the actual message definitions from the ERC-Protobufs repository.

Common Definitions (sensor.proto)

Location: ERC-Protobufs/components/sensor_board/sensor.proto

SensorState Enum

Shared across all sensor types - indicates the current operational state of a sensor.

enum SensorState {
  SENSOR_IDLE = 0;           // Sensor is idle/not currently sampling
  SENSOR_OPERATING = 1;      // Sensor is actively sampling/operating normally
  SENSOR_CALIBRATING = 2;    // Sensor is in calibration mode
  SENSOR_ERROR = 3;          // Sensor has encountered an error
}

GPS Sensor (gps_sensor.proto)

Location: ERC-Protobufs/components/sensor_board/gps_sensor.proto

Direction: Sensor Board → Navigation/Localization Systems

GPSFixQuality Enum

Indicates the type and quality of GPS fix obtained.

enum GPSFixQuality {
  NO_FIX = 0;       // No fix available
  GPS_FIX = 1;      // Standard GPS fix
  DGPS_FIX = 2;     // Differential GPS fix
  PPS_FIX = 3;      // PPS (Pulse Per Second) fix
  RTK_FIX = 4;      // Real-Time Kinematic fix
  RTK_FLOAT = 5;    // RTK float solution
}

GPSErrorCode Enum

Detailed error codes for GPS/GNSS sensor failures.

enum GPSErrorCode {
  GPS_NO_ERROR = 0;
  GPS_COMMUNICATION_FAILURE = 1;   // UART connection lost
  GPS_INVALID_DATA = 2;             // Data parsing or validation failed
  GPS_ANTENNA_FAULT = 3;            // GPS antenna disconnected or faulty
  GPS_LOW_SIGNAL_QUALITY = 4;       // Signal strength too weak for fix
}

SensorBoardGPSInfo Message

Complete GPS positioning and velocity information.

message SensorBoardGPSInfo {
  // GPS coordinates
  double latitude = 1;           // Degrees (positive = North, negative = South)
  double longitude = 2;          // Degrees (positive = East, negative = West)
  float altitude = 3;            // Meters above sea level
  
  // Velocity data
  float speed = 4;               // Speed in meters per second
  float heading = 5;             // Course over ground in degrees (0-360)
  
  // Position accuracy and quality
  float hdop = 6;                // Horizontal dilution of precision (lower is better)
  float vdop = 7;                // Vertical dilution of precision (lower is better)
  int32 satellites = 8;          // Number of satellites in view (up to 16)
  
  GPSFixQuality fix_quality = 9;
  
  SensorState state = 10;
  GPSErrorCode error_code = 11;  // Error code if state is SENSOR_ERROR
  
  // Timestamp from GPS
  int64 utc_timestamp = 12;      // Unix timestamp in milliseconds
}

IMU Sensor (imu_sensor.proto)

Location: ERC-Protobufs/components/sensor_board/imu_sensor.proto

Direction: Sensor Board → Motion Control/Attitude Systems

IMUErrorCode Enum

Detailed error codes for IMU sensor failures.

enum IMUErrorCode {
  IMU_NO_ERROR = 0;
  IMU_COMMUNICATION_FAILURE = 1;      // I2C/SPI connection lost
  IMU_CALIBRATION_REQUIRED = 2;       // Sensor needs calibration
  IMU_CALIBRATION_FAILED = 3;         // Calibration procedure failed
  IMU_INVALID_DATA = 4;               // Data out of valid range
  IMU_SENSOR_FAULT = 5;               // Hardware fault detected
  IMU_GYROSCOPE_ERROR = 6;            // Gyroscope component failure
  IMU_MAGNETOMETER_ERROR = 7;         // Magnetometer component failure
  IMU_ACCELEROMETER_ERROR = 8;        // Accelerometer component failure
}

SensorBoardIMUInfo Message

3-axis inertial measurement data (acceleration, angular velocity, magnetic field).

message SensorBoardIMUInfo {
  // 3-Axis Accelerometer data
  float accel_x = 1;             // X-axis acceleration
  float accel_y = 2;             // Y-axis acceleration
  float accel_z = 3;             // Z-axis acceleration
  
  // 3-Axis Gyroscope data
  float gyro_x = 4;              // X-axis angular velocity
  float gyro_y = 5;              // Y-axis angular velocity
  float gyro_z = 6;              // Z-axis angular velocity
  
  // 3-Axis Magnetometer data (9-axis IMU only)
  float mag_x = 7;               // X-axis magnetic field
  float mag_y = 8;               // Y-axis magnetic field
  float mag_z = 9;               // Z-axis magnetic field

  bool is_calibrated = 13;       // True if IMU has been calibrated on level surface
  
  SensorState state = 14;
  IMUErrorCode error_code = 15;  // Error code if state is SENSOR_ERROR
}

pH Sensor (ph_sensor.proto)

Location: ERC-Protobufs/components/sensor_board/ph_sensor.proto

Direction: Sensor Board → Environmental Monitoring Systems

PHErrorCode Enum

Detailed error codes for pH sensor failures.

enum PHErrorCode {
  PH_NO_ERROR = 0;
  PH_COMMUNICATION_FAILURE = 1;       // ADC connection lost
  PH_OUT_OF_RANGE = 2;                // Reading outside 0-14 range
  PH_CALIBRATION_REQUIRED = 3;        // Sensor needs calibration
  PH_INVALID_DATA = 4;                // Data validation failed
  PH_PROBE_FAULT = 5;                 // Electrode fault detected
  PH_TEMPERATURE_SENSOR_ERROR = 6;    // Temperature compensation sensor failed
}

SensorBoardPHInfo Message

Water quality measurement with temperature compensation.

message SensorBoardPHInfo {
  float ph_value = 1;            // Raw pH measurement (0-14 scale, 7 is neutral)
  float voltage = 2;             // Voltage reading from pH sensor in millivolts
  float temperature = 3;         // Temperature reading in Celsius (if external sensor available)
  
  SensorState state = 4;         // Current state of the pH sensor
  PHErrorCode error_code = 5;    // Error code if state is SENSOR_ERROR
}

Notes:

pH value is derived from voltage via linear calibration equation
40-sample moving average applied internally to reduce ADC noise
Temperature used for automatic compensation (default ~25°C)

Load Cell Sensor (load_cell.proto)

Location: ERC-Protobufs/components/sensor_board/load_cell.proto

Direction: Sensor Board → Arm Control/Gripper Systems

LoadCellErrorCode Enum

Detailed error codes for load cell sensor failures.

enum LoadCellErrorCode {
  LOAD_CELL_NO_ERROR = 0;
  LOAD_CELL_COMMUNICATION_FAILURE = 1;   // ADC connection lost
  LOAD_CELL_OUT_OF_RANGE = 2;            // Force measurement exceeds limits
  LOAD_CELL_CALIBRATION_REQUIRED = 3;    // Sensor needs calibration
  LOAD_CELL_INVALID_DATA = 4;            // Data validation failed
  LOAD_CELL_SENSOR_FAULT = 5;            // Hardware fault detected
}

SensorBoardLoadCellInfo Message

Force measurement for robotic gripper control and load monitoring.

message SensorBoardLoadCellInfo {
  uint32 sensor_index = 1;               // 0-based index of the load cell (0 or 1)
  float force_newtons = 2;               // Force in Newtons
  float mass_grams = 3;                  // Mass in grams (derived from force)
  int32 raw_counts = 4;                  // Raw ADC counts (for debugging)

  // Calibration status and parameters
  bool is_calibrated = 5;                // True if calibration parameters are valid
  float scale_newtons_per_count = 6;     // Conversion factor (N/count)
  int32 tare_offset_counts = 7;          // Zero-load ADC offset

  SensorState state = 8;
  LoadCellErrorCode error_code = 9;      // Error code if state is SENSOR_ERROR
}

Dual Sensor Support:

Up to 2 independent load cells (sensor_index 0 and 1)
Typically used on dual-pad grippers for load distribution feedback
Each sensor maintains independent calibration parameters
Enables slip detection via load imbalance analysis

Pressure Sensor (pressure_sensor.proto)

Location: ERC-Protobufs/components/sensor_board/pressure_sensor.proto

Direction: Sensor Board → Arm Control/Gripper Systems / Environmental Monitoring

PressureErrorCode Enum

Detailed error codes for pressure sensor failures.

enum PressureErrorCode {
  PRESSURE_NO_ERROR = 0;
  PRESSURE_COMMUNICATION_FAILURE = 1;    // I2C/ADC connection lost
  PRESSURE_OUT_OF_RANGE = 2;             // Reading exceeds sensor limits
  PRESSURE_CALIBRATION_REQUIRED = 3;     // Sensor needs calibration
  PRESSURE_INVALID_DATA = 4;             // Data validation failed
  PRESSURE_SENSOR_FAULT = 5;             // Hardware fault detected
}

SensorBoardPressureInfo Message

Pressure measurement for robotic gripper control and environmental sensing.

message SensorBoardPressureInfo {
  uint32 sensor_index = 1;               // 0-based index of the pressure sensor (0 or 1)

  // Pressure data
  float pressure_kpa = 2;                // Pressure in kilopascals
  float temperature_c = 3;               // Temperature in Celsius (if available)
  float voltage = 4;                     // Sensor output voltage (if available)

  // Calibration status
  bool is_calibrated = 5;                // True if calibration parameters are valid

  SensorState state = 6;
  PressureErrorCode error_code = 7;      // Error code if state is SENSOR_ERROR
}

Dual Sensor Support:

Up to 2 independent pressure sensors (sensor_index 0 and 1)
Primary use: gripper pad force feedback for PID control
Enables real-time grip force regulation and slip detection
Secondary uses: depth sensing, altitude sensing, system pressure monitoring

Board Diagnostics (diagnostics.proto)

Location: ERC-Protobufs/components/sensor_board/diagnostics.proto

Direction: Sensor Board → Debugging Board / Health Monitoring Systems

SensorBoardDiagnostics Message

Complete system health and status snapshot sent periodically (5 second default).

message SensorBoardDiagnostics {
  enum State {
    IDLE = 0;
    OPERATING = 1;
    CALIBRATING = 2;
    ERROR = 3;
  }

  State state = 1;                       // Overall board state
  SensorBoardPHInfo ph_sensor = 2;       // pH sensor status
  SensorBoardIMUInfo imu_sensor = 3;     // IMU sensor status

  // Overall sensor board health
  float board_temperature = 4;           // Board temperature in Celsius
  float board_voltage = 5;               // System voltage (3.3V supply)
  
  SensorBoardGPSInfo gps_sensor_1 = 6;   // GPS sensor status
}

Board States:

IDLE (0) - Board initialized but not actively polling sensors
OPERATING (1) - All sensors functioning normally, data being collected
CALIBRATING (2) - Board or sensors in calibration mode
ERROR (3) - Critical system failure detected

Health Indicators:

board_temperature - STM32H753 die temperature; normal range 25-75°C
board_voltage - 3.3V supply input; should be 3.0-3.6V
Embedded sensor states - Each sensor's current SensorState (IDLE/OPERATING/CALIBRATING/ERROR)

Error Code Pattern

All sensor error codes follow a consistent pattern:

enum XXXErrorCode {
  XXX_NO_ERROR = 0;                      // No error
  XXX_COMMUNICATION_FAILURE = 1;         // Hardware interface (I2C/SPI/UART/ADC) failure
  XXX_OUT_OF_RANGE = 2;                  // Reading outside valid sensor range
  XXX_CALIBRATION_REQUIRED = 3;          // Sensor needs calibration
  XXX_INVALID_DATA = 4;                  // Data validation/filtering failed
  XXX_SENSOR_FAULT = 5;                  // Hardware fault or component failure
  // Additional sensor-specific errors...
}

Integration into application:

if (gps_result.error_code == GPS_COMMUNICATION_FAILURE) {
    LOG_ERROR("GPS UART connection lost");
    diagnostics.gps_sensor_1.state = SENSOR_ERROR;
} else if (gps_result.error_code == GPS_NO_ERROR) {
    LOG_INFO("GPS position: %f, %f", gps_result.latitude, gps_result.longitude);
}

Network Transmission

Main Sensor Data:

Sent via individual sensor messages
Packaged into SensorBoardState (sensor.proto)
UDP broadcast to 192.168.0.255:7 (configurable)
Interval: 5 seconds default (configurable)
Encoding: Nanopb (lightweight protobuf for embedded)

Diagnostics Data:

Sent via SensorBoardDiagnostics message
UDP broadcast to 192.168.0.255:7 (same port)
Interval: 5 seconds (synced with main loop)
Contains snapshot of all sensor states + health metrics

Message Composition

The SensorBoardDiagnostics message is composed of individual sensor message types:

SensorBoardDiagnostics
├── state (Board state)
├── SensorBoardPHInfo
│   ├── ph_value
│   ├── voltage
│   ├── temperature
│   ├── state (SensorState)
│   └── error_code (PHErrorCode)
├── SensorBoardIMUInfo
│   ├── accel_x, accel_y, accel_z
│   ├── gyro_x, gyro_y, gyro_z
│   ├── mag_x, mag_y, mag_z
│   ├── is_calibrated
│   ├── state (SensorState)
│   └── error_code (IMUErrorCode)
├── board_temperature
├── board_voltage
└── SensorBoardGPSInfo
    ├── latitude, longitude, altitude
    ├── speed, heading
    ├── hdop, vdop, satellites
    ├── fix_quality
    ├── state (SensorState)
    ├── error_code (GPSErrorCode)
    └── utc_timestamp

Note: Not all proto files define load cells and pressure sensors in diagnostics.proto yet - they are sent as separate messages when available.

Setup of Embedded Ethernet

Sending your first message

Ethernet Testing

Extra Functions

Debugging

Issues

Starting with Protobufs

Design

Arm Board Protobuffers

Sensor Board Protobuf

Driving Board Protobuffers

Sensor Board Protobuf

Common Definitions (sensor.proto)

SensorState Enum

GPS Sensor (gps_sensor.proto)

GPSFixQuality Enum

GPSErrorCode Enum

SensorBoardGPSInfo Message

IMU Sensor (imu_sensor.proto)

IMUErrorCode Enum

SensorBoardIMUInfo Message

pH Sensor (ph_sensor.proto)

PHErrorCode Enum

SensorBoardPHInfo Message

Load Cell Sensor (load_cell.proto)

LoadCellErrorCode Enum

SensorBoardLoadCellInfo Message

Pressure Sensor (pressure_sensor.proto)

PressureErrorCode Enum

SensorBoardPressureInfo Message

Board Diagnostics (diagnostics.proto)

SensorBoardDiagnostics Message

Error Code Pattern

Network Transmission

Message Composition