PCB's

Sensor Board

All about the sensor board

Sensor Board

Overview

The Sensor Board is an embedded system that acquires environmental and process data from multiple sensors and actuates the sampling hardware (water pump). It integrates water quality (pH), motion (IMU), force (load cells), pressure (FSR pads), and water flow measurement, and transmits all data over Ethernet using Protocol Buffer encoding. It also receives control packets (for example pump commands) over the same link.

Implementation Status Disclaimer: The sensor board code was only partially tested and never fully implemented on hardware. Due to time constraints and other technical issues faced by the 2025-2026 team, several drivers remain compile gated or placeholder (pH ADC path, pressure ADC path, IMU bus access, flow sensor EXTI line). The load cell (HX711), pump (PWM), networking and protobuf pipeline are implemented in firmware; end to end validation on the assembled board was not completed.

Hardware Platform

Item

Value

Microcontroller

STM32H753ZI (NUCLEO-H753ZI board), ARM Cortex-M7 (480 MHz capable, currently clocked at 64 MHz, see STM32CubeMX Sensor Configuration)

Real-Time OS

FreeRTOS with CMSIS-RTOS V2

Ethernet

LAN8742 PHY, RMII, LwIP stack (static IP, no DHCP)

Serial logging

ST-Link VCP (USART3, 115200 baud)

FreeRTOS heap

64 KB (configTOTAL_HEAP_SIZE = 65536)

Message encoding

nanopb (Protocol Buffers), definitions in the ERC-Protobufs submodule

Key Board Features

Integrated Sensors and Actuators

Device

Model / Interface

Count

Firmware status

pH Sensor

DFRobot SEN0161, analog ADC

1

Driver complete, ADC path compile gated (PH_SENSOR_USE_ADC), poll returns RESULT_ERR_UNIMPLEMENTED until an ADC is enabled in CubeMX

IMU

TBD, I2C1 (PB8/PB9)

1

Data structure, math and validation helpers implemented; hardware poll is a placeholder

Load Cell (Weight)

HX711 24-bit ADC, GPIO bit-bang

2

Implemented, auto-tare on init, scale calibration API

Pressure (FSR)

Analog force sensing resistor pads, ADC

2

Driver complete, ADC path compile gated (PRESSURE_USE_ADC), poll returns RESULT_ERR_UNIMPLEMENTED until an ADC is enabled

Flow Sensor

FM-PS2216 (5.5 pulses/ml), GPIO EXTI pulse counting on PA4

1

Implemented; EXTI4 must still be enabled in CubeMX for pulses to be counted

Water Pump

Grothen 12 V DC mini peristaltic pump, single MOSFET on TIM3 CH3 PWM (PC8)

1

Implemented, open loop, unidirectional; health cross-checked against the flow sensor

Check this out for compiling code and more about project structure- Project Structure

Sensor Board

STM32CubeMX Sensor Configuration

This page documents the current STM32CubeMX configuration for the Sensor Board firmware and explains how to extend it for the remaining sensor interfaces (ADC, EXTI, I2C device setup) in a way that is safe for code generation.

Current CubeMX Snapshot

Item

Value

MCU

STM32H753ZITx (NUCLEO-H753ZI)

CubeMX Version

6.15.0

STM32Cube FW Package

STM32Cube FW_H7 V1.12.1

Build system

PlatformIO (env:sensor_board), stm32cube framework

Enabled CubeMX Components

Clock and Core Setup

Clock Configuration (from IOC)

Parameter

Value

HSE crystal value

8 MHz

SYSCLK

64 MHz

APB1

64 MHz

Note: the STM32H753 is capable of 480 MHz, but the current IOC runs the core at 64 MHz. Raising the clock requires PLL configuration in the Clock Configuration tab and re-validation of the Ethernet and FreeRTOS timing.

Cortex-M7 / MPU

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

PB12

ETH_TXD1

PB13

Sensor and Actuator Pins (labeled in IOC)

Label

Pin

Mode

Used by

FLOW_SENSOR

PA4

GPIO Input (EXTI4 not yet enabled)

Flow sensor pulse counting

WEIGHT_INPUT_1

PA5

GPIO Input

HX711 unit 0 DOUT

WEIGHT_INPUT_2

PA6

GPIO Input

HX711 unit 1 DOUT

WEIGHT_CLOCK_1

PC7

GPIO Output

HX711 unit 0 SCK

WEIGHT_CLOCK_2

PB5

GPIO Output

HX711 unit 1 SCK

IMU_I2C_Clock

PB8

I2C1_SCL (pull-up)

IMU

IMU_I2C_Data

PB9

I2C1_SDA (pull-up)

IMU

WATER_PUMP_PWM

PC8

TIM3_CH3 (PWM)

Pump MOSFET gate

PH_ANALOG_DATA

PD14

GPIO_Analog

pH sensor (see warning below)

FORCE_ANALOG_DATA_1

PD15

GPIO_Analog

Pressure/FSR sensor 0 (see warning below)

FORCE_ANALOG_DATA_2

PF3

GPIO_Analog

Pressure/FSR sensor 1 (PF3 = ADC3_INP5)

STEPPER_MOTOR_1..4

PD7, PD6, PD5, PD4

GPIO Output

Reserved for the sampling stepper

Warning: on the STM32H753, PD14 and PD15 have NO ADC function. The pH analog input and FORCE_ANALOG_DATA_1 must be moved to ADC-capable pins (for example PA0, PC0, or PF3-class pins) before the analog drivers can be enabled. PF3 maps to ADC3_INP5 and can be used as is.

Serial / COM

Signal

Pin

Note

USART1_TX / USART1_RX

PA9 / PA10

Spare asynchronous UART

USART3_TX / USART3_RX

PD8 / PD9

NUCLEO ST-Link VCP path, used by the logging system (hcom_uart[COM1])

RTOS Tasks and Interrupts

FreeRTOS Tasks (CMSIS V2)

Task

Priority

Stack (words)

Entry

defaultTask

24

128

StartDefaultTask (generated)

mainTask

39

2048

MainTask, "As external" (defined in src/sensor_board/main.c)

FreeRTOS heap: configTOTAL_HEAP_SIZE = 65536 (64 KB).

Interrupt Priorities (key entries)

IRQ

Priority

Notes

ETH_IRQn

5

Ethernet / LwIP path

DMA1_Stream0_IRQn

5

DMA

USART1_IRQn

5

Spare UART

EXTI15_10_IRQn

5

External interrupt group (user button)

TIM6_DAC_IRQn

15

HAL tick timebase (TIM6)

SysTick / PendSV

15

FreeRTOS kernel

Sensor Interface Status

What Is Already Configured in CubeMX

What Is Not Yet Modeled in CubeMX (TO DO once sensors are retrieved and assembled)

Important: the analog sensor drivers are compile gated (PH_SENSOR_USE_ADC, PRESSURE_USE_ADC) so the firmware links without hardware. When bringing up physical sensors, add the corresponding CubeMX peripherals first, then enable the build flags and bind the generated handles.

  1. Open components/sensor_board/firmware/firmware.ioc in STM32CubeMX.
  2. Add the required peripheral for the target sensor (ADC channel, EXTI line, or I2C settings).
  3. Assign and lock pins in the Pinout view; avoid overlap with RMII and COM pins.
  4. Configure clocks for new peripherals in Clock Configuration.
  5. Set NVIC priorities for new ISR sources so Ethernet and RTOS timing remain stable.
  6. Generate code with Keep User Code enabled.
  7. Rebuild using PlatformIO and validate startup and sensor polling.

Conflicts To Check Before Saving the .ioc File

Sensor Board

Sensor Basics Utility Library

The Sensor Basics utility library provides small validation and conversion helpers shared by the sensor drivers and the main application. These are basic features that could be used if required, but were made in "spare time".

Source Code Location

Files:

Dependencies:

pH Validation

validate_ph_value()

Validates that a pH value is within the acceptable range (0 to 14).

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;
}

Return values: RESULT_OK when the value is within range, RESULT_ERR_INVALID_DATA otherwise.

Note: ph_sensor_update() already clamps its output to 0..14, so this check only fails for values that bypass the driver (for example raw values received over the network).

IMU (Accelerometer) Validation

validate_accelerometer_value()

Validates one accelerometer axis. Valid range is -160.0 to +160.0 m/s², which corresponds to a typical ±16 g sensor range.

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;
}

validate_imu_data()

Validates all three accelerometer axes at once using the TRY macro for early return on the first invalid axis.

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;
}

Note: the IMU driver has its own richer validators (imu_validate_accelerometer_range, imu_validate_gyroscope_range, imu_validate_magnetometer_range) which the main loop uses. See the imu component.

Conversion Functions (declared, currently inactive)

The header declares four unit conversion helpers. Their implementations exist in sensor_basics.c but are commented out, so linking against them fails until they are re-enabled.

/* Temperature: F = C * 9/5 + 32,  C = (F - 32) * 5/9 */
result_t celsius_to_fahrenheit(float celsius, float *fahrenheit);
result_t fahrenheit_to_celsius(float fahrenheit, float *celsius);

/* Pressure: psi = bar * 14.5038,  bar = psi / 14.5038 */
result_t bar_to_psi(float bar, float *psi);
result_t psi_to_bar(float psi, float *bar);

Each returns RESULT_OK on success or RESULT_ERR_INVALID_ARG when the output pointer is NULL.

Implementation Status

Currently implemented (active):

Currently commented out (inactive):

Note: earlier drafts of this page documented GPS validation helpers (latitude, longitude, HDOP, satellite count). These functions do not exist in the current library since there is no GPS driver on the sensor board.

Error Handling Pattern

All validation functions follow the same pattern used across the firmware:

if (validate_ph_value(ph_value) == RESULT_OK) {
    diagnostics.ph_sensor.state = SensorState_SENSOR_OPERATING;
    diagnostics.ph_sensor.error_code = PHErrorCode_PH_NO_ERROR;
} else {
    diagnostics.ph_sensor.state = SensorState_SENSOR_ERROR;
    diagnostics.ph_sensor.error_code = PHErrorCode_PH_INVALID_DATA;
}

Testing

Test suite location: test/sensor_board/test_sensor_basics/

# Run only the 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

Current coverage: accelerometer boundary values (±160.0 accepted, ±160.1 rejected) and multi-axis combination. The temperature and pressure conversion tests exist in the file but are commented out together with their implementations.

Sensor Board

Architecture

Complete system overview: FreeRTOS task model, the sensor polling loop, protobuf encoding, UDP transmission, inbound packet dispatch, and the memory layout. All application logic lives in a single FreeRTOS task (MainTask) defined in src/sensor_board/main.c.

Initialization Sequence

Phase 1: Hardware Setup (init_board, before the kernel starts)

void init_board() {
  MPU_Config_wrapper();
  SCB_EnableICache();
  SCB_EnableDCache();
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  /* NOTE: no threads here, kernel not initialized yet.
   * osKernelInitialize() is called by cubemx_main.c afterwards. */
}

Phase 2: Driver Initialization (start of MainTask)

  1. BSP LEDs (Green, Blue, Red)
  2. Logging over the ST-Link VCP UART (LOG_init(&hcom_uart[COM1]), 115200 baud)
  3. IMU (imu_sensor_init)
  4. pH sensor (ph_sensor_init with 3.3 V reference)
  5. Two HX711 load cells with their GPIO map (PA5/PC7 and PA6/PB5), each powered up and auto-tared
  6. Two pressure/FSR sensors (pressure_sensor_init)
  7. Flow sensor (flow_sensor_init, pulse counting via EXTI callback)
  8. Pump (pump_init on TIM3 CH3 PWM, then commanded to 50 percent and enabled as a startup default)

Phase 3: Communication Setup

  1. ETH_init with static IP 192.168.0.111, netmask 255.255.255.0, gateway 192.168.0.1 and a link status callback that re-adds the static ARP entry when the link comes up
  2. MAC address filtering for three allowed source MACs (ETH_setup_MAC_address_filtering)
  3. Two statically allocated prioritised UDP transmit queues (80 entries each)
  4. Packet dispatcher registration for five inbound message types (pH, IMU, load cell, pressure, pump)
  5. ETH_udp_init(2, send_queues, DispatchPacket) and a static ARP entry for the destination board 192.168.0.222

Phase 4: Main Loop

The loop runs forever with a 5000 ms period (MAIN_TASK_DELAY_MS). Each iteration:

  1. Read free heap; if below 4096 bytes log CRITICAL and sleep 10 s instead of polling
  2. Toggle the three LEDs (visual heartbeat)
  3. Build a SensorBoardDiagnostics struct (state OPERATING)
  4. Poll pH, IMU, then load cells and pressure sensors (index loop over both units)
  5. Poll the flow sensor (rate computed from pulses counted by the EXTI ISR since the last poll)
  6. Build the pump status from commanded state, cross-checked against measured flow
  7. Wrap each sensor message in a PBEnvelope and send it as a UDP datagram to the sample board
  8. osDelay(MAIN_TASK_DELAY_MS)

Protobuf Encoding and UDP Transmission

Every outbound message is one PBEnvelope with a oneof payload. Encoding uses nanopb via pb_message_encode, which allocates a heap buffer that is freed after sending.

static void udp_send_envelope(uint8_t dest_ip[4], PBEnvelope *env) {
  if (!sendUDP) { return; }   /* transmit gate, false by default */
  uint8_t *encoded = NULL;
  size_t size = 0;
  result_t result = pb_message_encode(env, PBEnvelope_fields, &encoded, &size);
  if (result == RESULT_OK) {
    ETH_udp_send(dest_ip, PORT, encoded, (uint16_t)size, 1);
  }
  free(encoded);
}

Important: the static flag sendUDP in main.c is currently false, so envelope encoding and transmission are skipped entirely. Set it to true to actually transmit. There is a similar development flag skip_sensor_polling (currently false) that disables all sensor polling when true.

Inbound Packet Dispatcher

Received UDP packets are decoded by the shared packet dispatcher (components/common/packet_dispatcher). Handlers are registered with PACKET_HANDLER_CONFIG_STATIC per envelope payload tag:

Envelope tag

Handler

Behavior

ph_info

handle_sensor_ph_info

Log only

imu_info

handle_sensor_imu_info

Log only

load_cell_info

handle_sensor_load_cell_info

Log only

pressure_info

handle_sensor_pressure_info

Log only

pump_info

handle_sensor_pump_command

Actuates the pump: applies enabled, direction, and speed_percent to the hardware

Sensor Status Model

SensorState (operating state)

Code

Meaning

SENSOR_IDLE

Not connected, not implemented, or intentionally off

SENSOR_OPERATING

Normal operation, valid data

SENSOR_ERROR

Communication failure or invalid data

SensorStatus (connection status)

Code

Meaning

STATUS_OK

Healthy

STATUS_DISCONNECTED

No hardware detected (poll returned UNIMPLEMENTED or COMMS)

STATUS_ERROR

Unexpected failure

STATUS_INITIALIZING

Warming up (flow sensor first sample window)

Poll Result Mapping

handle_sensor_poll_result() maps driver results uniformly:

Every sensor produces one uniform log line per loop: name | STATUS | STATE | detail.

Pump Health Cross-Check

The pump is an open loop actuator (no current sense or fault line), so firmware cannot directly detect a connected pump. The only on-board proof that fluid is moving is the inline flow sensor, so the main loop derives pump status from it:

Memory Layout

Region

Use

FreeRTOS heap, 64 KB

Task stacks, queues, protobuf encode buffers (malloc/free per message)

0x30000000, 32 KB, MPU non-cacheable

Ethernet DMA descriptors and buffers

0x30004900, 16 KB

LwIP RAM heap (MEM_SIZE)

Static queues

Two UDP send queues, 80 entries each, allocated at compile time (xQueueCreateStatic)

Error Handling Strategy

Sensor Board

Configuration

Compile-time parameters, runtime flags, sensor calibration setup, network addressing, and performance tuning options for the sensor board firmware.

Main Loop Timing

/* src/sensor_board/main.c */
#define MAIN_TASK_DELAY_MS 5000   /* poll + transmit interval */

All sensors are polled and transmitted once per interval. Lowering this value increases network traffic and heap churn (one encode allocation per message).

Runtime Flags (main.c)

Flag

Default

Effect

sendUDP

false

When false, udp_send_envelope() returns immediately: nothing is encoded or transmitted. Set to true to enable network output.

skip_sensor_polling

false

When true, the pH/IMU/load cell/pressure polling block is skipped (flow and pump still run).

Heap Management

uint32_t free_heap = xPortGetFreeHeapSize();
if (free_heap < 4096U) {   /* critical threshold, was 8192U */
    LOGE(TAG, "CRITICAL: Low heap! Free: %lu bytes", free_heap);
    osDelay(10000);
    continue;
}

Network Configuration

All addresses live in components/common/networking_constants/ip_mac_constants.h:

#define NETWORK_IP       {192, 168, 0, 111}                     /* this board */
#define NETWORK_MAC      {0x00, 0x80, 0xe1, 0x00, 0x00, 0x00}

#define SAMPLE_BOARD_IP  {192, 168, 0, 222}                     /* UDP destination */
#define SAMPEL_BOARD_MAC {0x00, 0x43, 0x23, 0xee, 0x21, 0x64}

#define GATEWAY          {192, 168, 0, 1}
#define NETMASK          {255, 255, 255, 0}

#define PORT 1500                                               /* UDP port */

Changing the Destination Address or Port

  1. Edit SAMPLE_BOARD_IP / SAMPEL_BOARD_MAC (used both for sending and for the static ARP entry) or PORT in ip_mac_constants.h.
  2. Rebuild; no other file references the raw addresses.

MAC Address Filtering

Three source MACs are allowed through the hardware filter, configured in MainTask:

int mac1[6] = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66};
int mac2[6] = {0x12, 0x23, 0x34, 0x45, 0x56, 0x67};
int mac3[6] = {0x90, 0x2e, 0x16, 0xbe, 0x1b, 0x33};
ETH_setup_MAC_address_filtering(mac1, mac2, mac3);

UDP Transmit Queues

#define SENSOR_SEND_QUEUE_SIZE 80   /* entries per priority queue, x2 queues */

Sensor Hardware Build Flags

The analog drivers are compile gated so the firmware links without ADC hardware. Add these to build_flags in platformio.ini once the corresponding CubeMX peripherals exist:

Flag

Effect

-D PH_SENSOR_USE_ADC

Enables the pH ADC read path (optional: -D PH_SENSOR_ADC_HANDLE=hadc1, -D PH_SENSOR_ADC_MAX=65535, -D PH_SENSOR_ADC_TIMEOUT_MS=100)

-D PRESSURE_USE_ADC

Enables the pressure/FSR ADC read path; bind each unit with pressure_sensor_init_hw()

-D PUMP_MAX_RPM_EST=100

Override the pump RPM estimate used when converting duty cycle to speed_rpm

-D CONFIG_LOG_LEVEL=LOG_INFO

Log verbosity (already set in platformio.ini)

Sensor Calibration Configuration

pH Sensor

/* components/sensor_board/ph/ph_sensor.h */
#define PH_SAMPLE_COUNT   40     /* averaging buffer size */
#define PH_DEFAULT_SLOPE  3.5f   /* SEN0161 default: pH = 3.5 * V + offset */

/* runtime calibration */
ph_sensor_calibrate(&ph_sensor, offset, slope);
ph_sensor_reset_calibration(&ph_sensor);   /* offset 0, slope 3.5 */

Load Cell (HX711)

/* components/sensor_board/load_cell/load_cell_sensor.h */
#define LOAD_CELL_DEFAULT_N_PER_COUNT 1.0f  /* passthrough until calibrated */
#define LOAD_CELL_GAIN_PULSES         1U    /* 1 = ch A gain 128 */
#define LOAD_CELL_READY_TIMEOUT_MS    200U  /* wait for DOUT low */

/* runtime calibration */
load_cell_tare(&cell, 10);                 /* average 10 reads as zero */
load_cell_set_scale(&cell, n_per_count);   /* marks is_calibrated = true */

Pressure / FSR

/* kPa = voltage * scale_kpa_per_volt + offset_kpa */
pressure_sensor_set_calibration(&sensor, scale_kpa_per_volt, offset_kpa);

Flow Sensor

/* components/sensor_board/sampling/flow_sensor/flow_sensor.h */
#define FLOW_SENSOR_PULSES_PER_ML_X10 55U    /* FM-PS2216: 5.5 pulses/ml */
#define FLOW_SENSOR_SAMPLE_WINDOW_MS  1000U  /* rate calculation window */
#define FLOW_SENSOR_MAX_FLOW_ML_MIN   150U   /* plausibility clamp */

Changing the Sensor Poll Interval

  1. Edit MAIN_TASK_DELAY_MS in src/sensor_board/main.c.
  2. Keep it well above the slowest blocking read (HX711 ready wait can take up to 200 ms per cell).
  3. The flow rate is computed per poll from the pulse count, so the interval also sets flow rate resolution.

Enabling / Disabling Sensors

Sensor Board

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 (compile gated, see Hardware Status below)

Reference Voltage

Configurable at init (3.3 V used in main.c; SEN0161 itself prefers a stable 5.0 V supply)

Board pin

PD14, labeled PH_ANALOG_DATA (must be moved, PD14 has no ADC function)

Measurement Range

0 to 14 pH units (clamped in software)

Accuracy

±0.1 pH @ 25°C (sensor datasheet)

Sample Averaging

40 samples, min and max excluded

Hardware Status

No ADC is enabled in CubeMX yet, so the ADC path is compile gated by PH_SENSOR_USE_ADC. Without that flag, poll_ph_sensor() returns RESULT_ERR_UNIMPLEMENTED and the sensor reports IDLE / DISCONNECTED (the firmware still links and runs). To enable:

  1. In CubeMX enable an ADC (for example ADC1) and a channel on the pH input pin. PD14 (the current PH_ANALOG_DATA label) has NO ADC function on the STM32H753, so move the pH input to an ADC-capable pin (PA0, PC0, ...).
  2. The SEN0161 is a 5 V board with output up to about 3 V. The STM32 ADC tops out at 3.3 V, so power or scale the board so its output never exceeds 3.3 V.
  3. Build with -D PH_SENSOR_USE_ADC (optionally -D PH_SENSOR_ADC_HANDLE=hadc1, -D PH_SENSOR_ADC_MAX=65535).

Calibration Model

The sensor uses linear voltage-to-pH conversion (DFRobot SEN0161 formula):

pH = slope × Voltage + offset
Voltage = averaged_ADC / adc_max × reference_voltage

Default Parameters for SEN0161 @ 25°C:

The computed pH is clamped to the 0 to 14 range inside ph_sensor_update().

Data Structure

typedef struct {
    uint16_t raw_value;              /* averaged raw ADC value */
    float voltage;                   /* converted voltage */
    float ph_value;                  /* calculated pH (0-14), init 7.0 */
    float reference_voltage;         /* ADC reference */
    ph_calibration_t calibration;    /* { offset: float, slope: float } */
    uint16_t sample_buffer[40];      /* last 40 samples (PH_SAMPLE_COUNT) */
    uint8_t sample_index;            /* current position in buffer */
    uint8_t samples_collected;       /* samples collected so far (0-40) */
} ph_sensor_t;

Initialization & Usage

Initialize pH Sensor

ph_sensor_t ph_sensor;
ph_sensor_init(&ph_sensor, 3.3f);  /* 3.3 V reference, as in main.c */

Poll pH Sensor

result_t ph_result = poll_ph_sensor(&ph_sensor);

if (ph_result == RESULT_OK) {
    float ph_value, voltage;
    ph_sensor_get_value(&ph_sensor, &ph_value);
    ph_sensor_get_voltage(&ph_sensor, &voltage);
}
/* RESULT_ERR_UNIMPLEMENTED: ADC path not compiled in
 * RESULT_ERR_COMMS: HAL ADC start/conversion failed */

Manual Sample Addition

/* For manual sampling at regular intervals (e.g. every 20 ms) */
uint16_t adc_reading = 2048;
ph_sensor_add_sample(&ph_sensor, adc_reading);

/* Or feed a reading through the full pipeline (average + convert) */
ph_sensor_update(&ph_sensor, adc_reading, 4095);

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 (PH_SAMPLE_COUNT)

Method

Circular buffer average, minimum and maximum values excluded (DFRobot sample code algorithm); simple average while fewer than 5 samples collected

Purpose

Noise filtering and stable readings

Averaging Algorithm

1. ADC sample added to circular buffer
2. Buffer averaged with min and max excluded
3. Averaged value converted to voltage
4. Voltage converted to pH via calibration (slope, offset)
5. pH clamped to 0-14

Two-Point Calibration Procedure

Step 1: Neutral Point (pH 7.0)

1. Short the BNC input or immerse the electrode in pH 7.0 buffer solution
2. Wait for a stable reading (~2 minutes)
3. Record the reported pH value
4. offset = 7.0 - recorded_value

Step 2: Slope Calibration (pH 4.0 or 10.0)

1. Immerse the electrode in a second known pH solution (pH 4.0 buffer)
2. Wait for a stable reading
3. Adjust the board gain potentiometer until the reading is 4.0,
   or compute: slope = (pH_reference - 7.0) / (V_reference - V_neutral)
4. Apply with ph_sensor_calibrate(&sensor, offset, slope)

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 (as in main.c)

if (ph_result == RESULT_ERR_UNIMPLEMENTED || ph_result == RESULT_ERR_COMMS) {
    /* Hardware not connected / ADC not enabled */
    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_value) == RESULT_OK) {
        diagnostics.ph_sensor.state = SensorState_SENSOR_OPERATING;
        diagnostics.ph_sensor.error_code = PHErrorCode_PH_NO_ERROR;
    } else {
        diagnostics.ph_sensor.state = SensorState_SENSOR_ERROR;
        diagnostics.ph_sensor.error_code = PHErrorCode_PH_INVALID_DATA;
    }
}

Integration Notes

Sensor Board

IMU

The Inertial Measurement Unit (IMU) provides three-axis acceleration, angular velocity, and magnetic field measurements for attitude determination and motion analysis.

Hardware

Parameter

Value

Device

Xsens Avior (Xbus protocol, MTi-1-series compatible pipe interface)

Interface

I2C1, pins PB8 (IMU_I2C_Clock) / PB9 (IMU_I2C_Data), internal pull-ups enabled

I2C address

0x6B (7-bit, MTi-1 series default, override with -D XSENS_I2C_ADDR_7BIT)

Output rate

100 Hz requested for accel/gyro/mag (XSENS_OUTPUT_RATE_HZ)

I2C timeout

100 ms (XSENS_I2C_TIMEOUT_MS)

Important: the pipe opcodes, default I2C address, and Xbus data identifiers used by the driver are the documented Xsens MTi-1-series values. The Avior is Xbus-compatible, but confirm these against the Avior datasheet (mtidocs.xsens.com) and override with -D build flags if your unit differs. The driver was never validated against physical hardware.

Communication Protocol (Xbus over I2C)

Xbus messages move through "pipe" opcodes used as an 8-bit register address:

Xbus frame: [0xFA][0xFF][MID][LEN][DATA...][CHK]
CHK makes (BID + MID + LEN + DATA + CHK) & 0xFF == 0

On the first poll the driver configures the device once: GoToConfig, SetOutputConfiguration (acceleration + rate of turn + magnetic field at 100 Hz, float32), GoToMeasure. If configuration fails, poll returns RESULT_ERR_COMMS (device not responding on I2C).

Data Structure

typedef struct {
    float accel[3];            /* [X, Y, Z] acceleration, m/s² */
    float gyro[3];             /* [X, Y, Z] angular velocity, °/s
                                  (converted from rad/s by the driver) */
    float mag[3];              /* [X, Y, Z] magnetic field, Xsens arbitrary
                                  units (~1.0 = local Earth field), NOT µT */
    uint32_t timestamp;        /* Current reading timestamp (HAL_GetTick ms) */
    uint32_t last_timestamp;   /* Previous reading timestamp */
} imu_data_t;

Unit notes: the gyroscope values are converted from rad/s to °/s inside the driver. The Xsens magnetic field output is in arbitrary units where roughly 1.0 equals the local Earth field; it is stored as-is and must be scaled externally if µT are needed.

Initialization & Usage

Initialize IMU

imu_data_t imu_data;
imu_sensor_init(&imu_data);   /* zeroes the structure */

Poll IMU Data

result_t imu_result = poll_imu_sensor(&imu_data);

if (imu_result == RESULT_OK) {
    /* Acceleration (m/s²) */
    float accel_x = imu_data.accel[0];
    float accel_y = imu_data.accel[1];
    float accel_z = imu_data.accel[2];

    /* Angular velocity (°/s) */
    float gyro_x = imu_data.gyro[0];
    float gyro_y = imu_data.gyro[1];
    float gyro_z = imu_data.gyro[2];

    /* Magnetic field (Xsens arbitrary units) */
    float mag_x = imu_data.mag[0];
    float mag_y = imu_data.mag[1];
    float mag_z = imu_data.mag[2];
}
/* RESULT_ERR_COMMS: device not responding, or no fresh sample ready yet */

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);
/* |a| = sqrt(ax² + ay² + az²), useful for impact and free-fall detection */

Orientation Helpers (from the gravity vector)

float pitch_deg = imu_get_pitch(&imu_data); /* atan2(ay, sqrt(ax²+az²)) in degrees */
float roll_deg  = imu_get_roll(&imu_data);  /* atan2(ax, sqrt(ay²+az²)) in degrees */
/* Assumes the device is relatively stationary */

Gyroscope Drift Check

/* true when all gyro axes are below the threshold (device at rest) */
bool stable = imu_check_gyroscope_drift(&imu_data, 1.0f);

Copying Data for Another Context

imu_data_t imu_copy;
imu_sensor_read(&imu_data, &imu_copy);
/* Plain struct copy, no locking: safe only if the source is not
 * being updated concurrently */

Sensor Ranges Used by the Driver Validators

Measurement

Accepted Range

Units

Acceleration

±16 g (±156.9 m/s²)

m/s²

Angular Velocity

±2000

°/s

Magnetic Field

±4900

driver limit (see unit note above)

Conversion Reference

From

To

Factor

g

m/s²

× 9.80665

rad/s

°/s

× 180/π (applied inside the driver)

Gauss

µT

× 100

Validation Functions

/* Driver-level validators (used by the main loop) */
bool imu_validate_accelerometer_range(imu_data_t *imu);  /* ±16 g in m/s² */
bool imu_validate_gyroscope_range(imu_data_t *imu);      /* ±2000 °/s */
bool imu_validate_magnetometer_range(imu_data_t *imu);   /* ±4900 */

/* Utility-library validators (sensor_basics.h) */
result_t validate_accelerometer_value(float accel_value); /* ±160 m/s² */
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;
    float mag_x;
    float mag_y;
    float mag_z;
    SensorState state;
    IMUErrorCode error_code;
}

enum IMUErrorCode {
    IMU_NO_ERROR = 0;
    IMU_COMMUNICATION_FAILURE = 1;
    IMU_ACCELEROMETER_ERROR = 2;
    IMU_GYROSCOPE_ERROR = 3;
    IMU_MAGNETOMETER_ERROR = 4;
}

Common Applications

Impact Detection

float mag = imu_get_acceleration_magnitude(&imu_data);
if (mag > IMPACT_THRESHOLD) {
    /* High acceleration detected */
}

Tilt Detection

float pitch = imu_get_pitch(&imu_data);
float roll  = imu_get_roll(&imu_data);

Motion Classification

/* Static vs dynamic based on gyro magnitude */
float gyro_mag = sqrtf(gyro_x*gyro_x + gyro_y*gyro_y + gyro_z*gyro_z);

Integration Notes

Sensor Board

Load Cell

Load cells measure force/weight to detect object presence, evaluate structural loading, or monitor mechanical stress. The system supports a dual load cell configuration, each read through its own HX711 24-bit ADC using GPIO bit-banging. This is the most complete sensor driver on the board: it talks to real hardware with no compile gate.

Hardware Specifications

Parameter

Value

Sensor Count

2 (independent)

ADC

HX711 24-bit, one per load cell

Interface

GPIO bit-bang (DOUT input, SCK output)

Gain

Channel A, gain 128 (LOAD_CELL_GAIN_PULSES = 1)

Measurement

Force (Newtons) / Mass (grams) after calibration; raw counts always available

Ready timeout

200 ms (LOAD_CELL_READY_TIMEOUT_MS)

Supply

HX711 VCC 2.7 to 5.5 V, GND common with the STM32

Wiring and Pin Map (from firmware.ioc)

Unit

HX711 DOUT (data, low = ready)

HX711 SCK (clock)

0

PA5 (WEIGHT_INPUT_1)

PC7 (WEIGHT_CLOCK_1)

1

PA6 (WEIGHT_INPUT_2)

PB5 (WEIGHT_CLOCK_2)

Data Structure

typedef struct {
  int32_t raw_counts;               /* 24-bit two's complement reading */
  float force_newtons;
  float mass_grams;
  float scale_newtons_per_count;    /* default 1.0 (passthrough) */
  int32_t tare_offset_counts;
  bool is_calibrated;               /* true once load_cell_set_scale() called */
  bool read_ok;                     /* true if the last poll succeeded */

  /* HX711 hardware binding (set by load_cell_sensor_init_hw) */
  GPIO_TypeDef *dout_port;
  uint16_t dout_pin;
  GPIO_TypeDef *sck_port;
  uint16_t sck_pin;
  uint8_t gain_pulses;
} load_cell_data_t;

Initialization

Initialize Load Cells (as in main.c)

load_cell_data_t load_cell_data[2];

/* Unit 0: DOUT = PA5, SCK = PC7. Unit 1: DOUT = PA6, SCK = PB5. */
load_cell_sensor_init_hw(&load_cell_data[0], GPIOA, GPIO_PIN_5, GPIOC, GPIO_PIN_7);
load_cell_sensor_init_hw(&load_cell_data[1], GPIOA, GPIO_PIN_6, GPIOB, GPIO_PIN_5);
/* init_hw powers up the HX711 and auto-tares */

/* Alternative: load_cell_sensor_init(&data) zero-initialises WITHOUT a
 * hardware binding; poll() then returns RESULT_ERR_UNIMPLEMENTED */

Poll Load Cell Sensor

result_t lc_result = poll_load_cell_sensor(&load_cell_data[i]);

Data Access Functions

float force, scale;
float mass;
int32_t counts, tare;
bool valid;

load_cell_get_force_newtons(&cell, &force);
load_cell_get_mass_grams(&cell, &mass);
load_cell_get_raw_counts(&cell, &counts);
load_cell_get_calibration(&cell, &scale, &tare);
load_cell_sensor_is_valid(&cell, &valid);

Calibration Procedure

Two-Step Calibration

Step 1: Tare (Zero Load)

/* With nothing on the cell: average N raw reads and store as zero offset.
 * init_hw already does this automatically at startup. */
load_cell_tare(&cell, 10);

Step 2: Span (Known Weight)

/* Place a known mass, read raw counts, then:
 *   scale = known_force_newtons / (raw_counts - tare_offset_counts)   */
load_cell_set_scale(&cell, newtons_per_count);   /* sets is_calibrated = true */

Measurement Formulas

force_newtons = (raw_counts - tare_offset_counts) × scale_newtons_per_count
mass_grams    = force_newtons / 9.81 × 1000

Note: before calibration the default scale is 1.0 (passthrough): raw_counts is trustworthy but force_newtons and mass_grams are not physical units yet.

Protobuf Message Format

message SensorBoardLoadCellInfo {
    uint32 sensor_index;            /* 0 or 1 */
    float force_newtons;
    float mass_grams;
    int32 raw_counts;
    float scale_newtons_per_count;
    int32 tare_offset_counts;
    bool is_calibrated;
    SensorState state;
    LoadCellErrorCode error_code;   /* NO_ERROR, COMMUNICATION_FAILURE, INVALID_DATA */
}

Unit Conversions

From

To

Factor

Newtons

kilograms-force (kgf)

÷ 9.81

Newtons

pounds-force (lbf)

÷ 4.448

grams

kilograms

÷ 1000

Integration Notes

Sensor Board

Pressure Sensor

The pressure sensors are analog force sensing resistor (FSR) pads read via ADC, intended primarily for robotic gripper force feedback: grip force sensing, object presence detection, and load distribution across two gripper pads. The system supports a dual sensor configuration.

Hardware Specifications

Parameter

Value

Sensor Count

2 (independent)

Interface

Analog ADC (compile gated, see Hardware Status below)

Board pins

PD15 (FORCE_ANALOG_DATA_1), PF3 (FORCE_ANALOG_DATA_2)

Output unit

kPa via linear conversion, plus raw voltage and temperature field

Hardware Status

The ADC path is compile gated by PRESSURE_USE_ADC because no ADC is enabled in CubeMX yet. Without the flag, poll_pressure_sensor() returns RESULT_ERR_UNIMPLEMENTED and both sensors report IDLE / DISCONNECTED (the firmware still links). To enable:

  1. In CubeMX enable an ADC and the channel(s) for the force pins. On the STM32H753, PD15 has NO ADC function and PF3 = ADC3_INP5, so FORCE_ANALOG_DATA_1 must be moved to an ADC-capable pin.
  2. Build with -D PRESSURE_USE_ADC.
  3. Bind each unit with pressure_sensor_init_hw().

Conversion Model

voltage      = raw / adc_max × reference_voltage
pressure_kpa = voltage × scale_kpa_per_volt + offset_kpa

Defaults: scale_kpa_per_volt = 1.0, offset_kpa = 0.0 (passthrough until calibrated).

Data Structure

typedef struct {
  float pressure_kpa;
  float temperature_c;
  float voltage;
  bool is_calibrated;
  bool read_ok;              /* true if the last poll read succeeded */

  /* ADC binding (set by pressure_sensor_init_hw) */
  void *adc_handle;          /* ADC_HandleTypeDef* (void* keeps header HAL-free) */
  uint32_t adc_channel;      /* ADC_CHANNEL_x */
  uint32_t adc_max;          /* full-scale count (e.g. 65535 for 16-bit) */
  float reference_voltage;   /* ADC Vref+ in volts */
  float scale_kpa_per_volt;  /* linear gain (default 1.0) */
  float offset_kpa;          /* linear offset (default 0.0) */
} pressure_sensor_data_t;

Initialization

Initialize Pressure Sensors (as in main.c)

pressure_sensor_data_t pressure_data[2];
for (size_t i = 0; i < 2; i++) {
    pressure_sensor_init(&pressure_data[i]);
}

/* Once an ADC exists, bind it per unit: */
pressure_sensor_init_hw(&pressure_data[1], &hadc3, ADC_CHANNEL_5,
                        65535U, 3.3f);

Poll Pressure Sensor

result_t pr_result = poll_pressure_sensor(&pressure_data[i]);

Data Access Functions

float kpa, temp_c, voltage;
bool valid;

pressure_sensor_get_pressure_kpa(&sensor, &kpa);
pressure_sensor_get_temperature_c(&sensor, &temp_c);
pressure_sensor_get_voltage(&sensor, &voltage);
pressure_sensor_is_valid(&sensor, &valid);

Calibration

/* kPa = V × scale + offset; marks the sensor calibrated */
pressure_sensor_set_calibration(&sensor, scale_kpa_per_volt, offset_kpa);

Pressure Unit Conversions

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

Function-based conversions (bar_to_psi, psi_to_bar) are declared in the utility library but currently commented out; see Sensor Board Utility Library.

Protobuf Message Format

message SensorBoardPressureInfo {
    uint32 sensor_index;            /* 0 or 1 */
    float pressure_kpa;
    float temperature_c;
    float voltage;
    bool is_calibrated;
    SensorState state;
    PressureErrorCode error_code;   /* NO_ERROR, COMMUNICATION_FAILURE, INVALID_DATA */
}

Applications

Robotic Gripper Control (Primary Use Case)

Possible Secondary Uses (not implemented)

Integration Notes

Sensor Board

Testing

Test organization, the Unity testing framework usage, coverage per suite, manual hardware testing checklists and a debugging/troubleshooting guide. Reminder: the sensor board code was only partially tested; unit tests cover the pure-logic parts of the drivers, and end to end hardware validation was not completed by the 2025-2026 team.

Test Organization

Suite

Location

test_sensor_basics

test/sensor_board/test_sensor_basics/test_sensor_basics.c

test_ph_sensor

test/sensor_board/test_ph_sensor/test_ph_sensor.c

test_imu_sensor

test/sensor_board/test_imu_sensor/test_imu_sensor.c

Test Framework

Building and Running Tests

# All sensor board tests
pio test -e sensor_board

# One suite
pio test -e sensor_board -f test_ph_sensor

# Verbose output
pio test -e sensor_board -f test_sensor_basics -v

Coverage Per Suite

test_sensor_basics

test_ph_sensor

test_imu_sensor

Manual Hardware Testing Checklist

  1. Flash with pio run -e sensor_board -t upload and open the serial monitor at 115200 baud
  2. Confirm the boot banner and each "init completed" line (IMU, pH, load cells, pressure, flow, pump, Ethernet)
  3. Confirm the three LEDs toggle every 5 seconds (loop heartbeat)
  4. Check the per-sensor status lines: connected hardware should read OPERATING | OK, absent hardware IDLE | DISCONNECTED
  5. Load cells: press on each cell and watch raw_counts/force change; verify tare at startup reads near zero
  6. Flow and pump: with tubing wet, enabling the pump must produce flow pulses; "commanded on but no flow detected" indicates a dry/absent pump or a not-configured EXTI4 line
  7. Network: set sendUDP = true, then capture UDP datagrams on port 1500 at 192.168.0.222 and decode with the PBEnvelope schema
  8. Send a SensorBoardPumpInfo command packet and verify the pump speed changes

Debugging & Troubleshooting

Issue

Cause

Solution

Sensor IDLE / DISCONNECTED

Not connected, or driver compile gated

Check wiring; for pH/pressure verify the PH_SENSOR_USE_ADC / PRESSURE_USE_ADC build flags and the CubeMX ADC config

Sensor ERROR

Communication failure

Verify HX711 wiring and timing, I2C address and pull-ups, ADC channel binding

Invalid data

Out of range values

Check calibration parameters (pH slope/offset, load cell scale/tare, pressure scale/offset)

Flow always 0

EXTI4 not enabled in CubeMX

Configure PA4 as EXTI4 rising edge and enable the EXTI4 NVIC line

Pump OPERATING / DISCONNECTED

No flow while commanded on

Pump absent, dry, or stalled; or the flow sensor is not installed/configured

No UDP packets

Transmit gate or addressing

Set sendUDP = true; check IP/MAC constants, MAC filtering, and that port 1500 is not blocked

Low heap warning

Memory leak or queue growth

Review protobuf encode/free paths and UDP queue sizes

Serial monitor silent

Wrong port or baud

Check the ST-Link COM port and 115200 baud; verify LOG_init ran

Sensor Board

Reference

Source code references, build configuration, hardware datasheet pointers, useful commands and the pre-deployment checklist. If you made it till here, you a true G.☮️

Source Code References

Main Application

File

Purpose

src/sensor_board/main.c

Main entry point, MainTask, sensor loop, packet handlers

Sensor and Actuator Drivers

Component

Location

IMU

components/sensor_board/imu/imu_sensor.h / .c

pH

components/sensor_board/ph/ph_sensor.h / .c

Load Cell (HX711)

components/sensor_board/load_cell/load_cell_sensor.h / .c

Pressure (FSR)

components/sensor_board/pressure/pressure_sensor.h / .c

Flow Sensor

components/sensor_board/sampling/flow_sensor/flow_sensor.h / .c

Pump

components/sensor_board/sampling/pump/pump.h / .c

Utilities

components/sensor_board/sensor_basics/sensor_basics.h / .c

Shared Components

Component

Location

Networking (LwIP glue, UDP)

components/common/networking/

Network addresses and port

components/common/networking_constants/ip_mac_constants.h

Packet dispatcher

components/common/packet_dispatcher/

Protobuf encode/decode helpers

components/common/pb_message/

Result codes and TRY macro

components/common/result/

Logging

components/common/logging/

Protobuf Definitions

Message definitions (PBEnvelope, SensorBoardPHInfo, SensorBoardIMUInfo, SensorBoardLoadCellInfo, SensorBoardPressureInfo, SensorBoardFlowSensorInfo, SensorBoardPumpInfo, SensorBoardDiagnostics) live in the ERC-Protobufs git submodule and are compiled to C by nanopb during the PlatformIO build. If the build cannot find the .pb.h headers, initialize the submodule:

git submodule update --init ERC-Protobufs

Build Configuration

File

Purpose

platformio.ini

Build configuration for all boards (env:sensor_board for this one)

components/sensor_board/firmware/firmware.ioc

CubeMX device configuration

components/sensor_board/STM32H753XX_FLASH.ld

Linker script

Development Workflow

Useful Commands (PlatformIO CLI)

Check this out for compiling code and more about project structure- Project Structure

# Build the sensor board firmware
pio run -e sensor_board

# Flash to the Nucleo board
pio run -e sensor_board -t upload

# Serial monitor (115200 baud)
pio device monitor -b 115200

# Run the unit tests
pio test -e sensor_board

Development Cycle

  1. Change peripherals in CubeMX (firmware.ioc), regenerate with Keep User Code
  2. Implement or update the driver in components/sensor_board/
  3. Build and run unit tests on the host
  4. Flash, watch the serial log, verify the per-sensor status lines
  5. Enable sendUDP and verify packets on the network

Hardware References

Device

Model

Protocol

Note

Microcontroller

STM32H753ZI (NUCLEO-H753ZI)

n/a

ARM Cortex-M7, 480 MHz capable (running at 64 MHz), 2 MB Flash; ST STM32H7 reference manual

Ethernet PHY

LAN8742

RMII

10/100 Mbps auto-negotiation

pH

DFRobot SEN0161

Analog ADC

40-sample averaging, 5 V board (scale output below 3.3 V)

IMU

Xsens Avior

I2C1 (PB8/PB9), Xbus

Address 0x6B, 100 Hz; driver untested on hardware (mtidocs.xsens.com)

Load Cell ADC

HX711 (×2)

GPIO bit-bang

24-bit, channel A gain 128

Pressure

FSR pads (×2)

Analog ADC

Compile gated, needs ADC in CubeMX

Flow

FM-PS2216

GPIO EXTI pulses

40 to 150 ml/min, 5.5 pulses/ml

Pump

Grothen 12 V DC mini peristaltic

PWM (TIM3 CH3)

Single MOSFET, unidirectional, open loop

Network Quick Reference

Item

Value

Board IP

192.168.0.111 (static, no DHCP)

Destination (sample board)

192.168.0.222

UDP port

1500

Netmask / Gateway

255.255.255.0 / 192.168.0.1

Quick Reference Checklist

Before Deployment

Monitoring in Production

Hope you had fun.☮️ End of documentation for the Sensor Board.

May The Force Be With You or Live Long and Prosper, depending on what you like.... but remember the Dark Side always has cooler toys

The Sensor Board is the coolest board ~ Mybrosky

Debugging Board

Lil gameboy doodad

Debugging Board

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:

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

Display

Used for quick, local feedback without needing a laptop.

Input interface (buttons / panel)

Debugging Board

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:

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

This provides sufficient resolution for:

Internal GRAM (Frame Buffer)

The controller includes internal Graphics RAM (GRAM), which stores pixel data.

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:

Typical operations include:

Display Orientation and Addressing

The controller supports:

This allows:

Hardware Reset and Initialization

The display requires:

These typically configure:

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:

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.

Debugging Board

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:

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:

It is not responsible for:

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:

Display control layer

These functions manage display state and configuration:

Primitive drawing layer

These functions draw directly to the screen:

Utility rendering layer

These functions build on the primitives to provide:

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:

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:

This is a performance and stack/RAM tradeoff parameter.

Color Definitions

The header provides a set of named RGB565 color constants, for example:

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:

  1. display enable
  2. SPI init hook
  3. hardware reset
  4. software reset
  5. a full controller configuration sequence
  6. exit from sleep mode
  7. display on
  8. initial screen rotation selection

Initialization sequence contents

The function writes a fixed command sequence configuring:

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:

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:

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:

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:

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:

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:

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

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:

Rendering behavior

For each bit:

Use case

This is useful for:

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:

  1. generating a 1bpp bitmap for one rounded corner
  2. rotating that bitmap to obtain all four corners
  3. drawing the four corner bitmaps
  4. 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:

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

Use case

This function is appropriate when the UI wants rounded bordered rectangles without a full framebuffer.

Debugging Board

Menu Driver - Overview

Purpose

The menu driver is a page-based UI framework for an embedded display (ILI9341).

It defines:

Architecture Position

[ Application Logic ]        
↓[ Menu Driver ]        
↓[ ILI9341 Driver ]        
↓[ SPI / Hardware ]

It does not:

It does:

1.3 Design Model

Everything revolves around:

“A UI is a collection of pages with lifecycle and state.”

Each page has:

         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  │
              └──────────────────┘
Debugging Board

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:

Debugging Board

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:

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:

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:

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:

Update

void (*update)(struct menu_manager_t *manager);

Handles input processing and state updates.

This function is expected to:

Render

void (*render)(struct menu_manager_t *manager);

Responsible for drawing the page to the display.

This function should:

Destruction

void (*destruct)(menu_page_state *state);

Handles cleanup when the page is no longer active.

In embedded systems, this typically involves:

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:

Does NOT:

Debugging Board

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:

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:

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 ] → [ 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:

entry_icons

Pointer to icon data associated with each entry.

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:

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:

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:

Relationship to Menu System

The list page enables hierarchical navigation through:

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: