H Bridge PCB

H-Bridge PCB Project

Project Description

This project involves the design and implementation of an educational single-phase H-Bridge inverter controlled by an Espressif ESP32.
The system demonstrates bipolar sinusoidal PWM (SPWM) operation with closed-loop VRMS amplitude control and a browser-based interface for monitoring and control.
The H-Bridge can drive loads with the following ratings:

• Input Voltage: 24 V
• Input Current: up to 10 A
• Power: ≈ 240 W

Features

• Fixed switching frequency: 35 kHz
• Fixed output frequency: 50 Hz
• Bipolar SPWM modulation (only)
• Closed-loop VRMS control using PI regulation
• Web-based UI (HTTP + WebSocket) for control and telemetry
• Input/Output power measurement
• Overcurrent protection using INA228 (auto driver shutdown + UI fault latch)

The project consists of two main components:

1. H_Bridge_PCB_Design — KiCad PCB layout and schematic.
2. H_Bridge_PCB_Code — Firmware for the ESP32 controller.

Directory Structure

Directory Structure

H_Bridge_PCB_Project/
├── H_Bridge_PCB_Design/        # KiCad design files
├── H_Bridge_PCB_Code/          # ESP32 firmware
│   ├── include/                # Header files
│   │   ├── Controller.h
│   │   ├── I2C.h
│   │   ├── Input_meas.h
│   │   ├── mutexdefinitions.h
│   │   ├── Output_meas.h
│   │   ├── PWM.h
│   │   ├── spi_sampler.h
│   │   ├── Tasks.h
│   │   └── webserver.h
│   │
│   ├── src/                    # Source files
│   │   ├── Controller.cpp
│   │   ├── I2C.cpp
│   │   ├── Input_meas.cpp
│   │   ├── Output_meas.cpp
│   │   ├── PWM.cpp
│   │   ├── spi_sampler.cpp
│   │   ├── Tasks.cpp
│   │   ├── webserver.cpp
│   │   └── main.cpp

Requirements

Hardware:

• PCB based on KiCad design
• 24 V DC power supply (≥ 10 A)
• Resistive or inductive load (max ≈ 240 W)
• Gate drivers with integrated dead-time
• INA228 current/voltage monitor for input sensing

Software:

• KiCad — PCB design
• PlatformIO — firmware build
• VS Code — recommended IDE

Webserver

The ESP32 provides a built-in Wi-Fi access point and hosts a web-based interface for control and measurement visualization.

Connect to WLAN Access Point

• SSID: H_Bridge_Control
• Password: 12345678

Open the web interface:

👉 http://192.168.4.1/

Functions:

• Start/Stop the inverter
• Set VRMS target
• Display live telemetry (Vin, Iin, VRMS, IRMS, PF, P, Q, f)
• View and acknowledge overcurrent faults

Code

The firmware is implemented in C++ (Arduino / FreeRTOS).
The web interface is built with HTML, JavaScript, and CSS.

Flowchart

Code Documentation

Brief overview of the most relevant components.

Inverter Implementation (PWM.cpp)

Implements the real-time control of the full-bridge inverter:

• startInverter() — Initializes and enables PWM output.
• stopInverter() — Stops PWM and resets inverter state.
• generateSPWM() — Produces bipolar SPWM using a sine table.
• begin() — Configures LEDC channels, frequency, and timers.
• getMeasurements() — Retrieves latest measurement snapshot.
• computePI() — Executes PI algorithm to maintain VRMS target.
• loop() — Runs the inverter control logic at fixed timing intervals.

Controller Implementation (Controller.cpp)

Implements the PI controller used to regulate the inverter’s RMS output voltage:

• PIController() — Initializes PI gains, integrator state, limits, and VRMS target.
• ControlRMS() — Computes RMS error and updates the global Q10 amplitude factor atomically.
• compute() — Executes PI algorithm with anti-windup and output clamping to min/max limits.
• g_amp_q10 — Global Q10-formatted amplitude value used by the SPWM stage.

I²C Bus Setup (I2C.cpp)

Implements the I²C interface for the INA228 current/voltage sensor:

• I2CINA — Dedicated I²C bus instance (port 0) used by the input measurement subsystem.

Input Measurement (Input_meas.cpp)

Implements DC input voltage, current, and power measurement using INA228:

• init() — Initializes I²C bus, scans for devices, configures INA228, and sets averaging/timing.
• init1() — Lightweight I²C initialization helper without full sensor setup.
• configure_overcurrent_alert_only() — Configures INA228 alert registers for shunt overcurrent shutdown.
• getVoltage() — Reads and returns the DC input voltage in volts.
• getCurrent() — Reads and returns the shunt current in amperes.
• getPower() — Reads and returns the input power in watts with simple error rejection.
• measurementall() — Updates the shared input measurement buffer (voltage, current, power) in a mutex-protected way and returns it.
• scanI2C() — Scans the I²C bus, prints found devices, and restarts the bus if no device is detected.

Main Application (main.cpp)

Implements system bring-up and FreeRTOS task orchestration:

• setup() — Initializes serial logging, mutexes, input measurement, Wi-Fi AP, webserver, SPI measurement engines, safety pins, and the overcurrent interrupt; then creates all application tasks.
• loop() — Empty main loop; periodically yields since all logic is implemented in FreeRTOS tasks.
• Task handles — Stores references to sampler, analyzer, WebSocket, controller, printer, and emergency stop tasks for debugging/management.

Mutex Definitions (mutexdefinitions.cpp)

Implements globally shared FreeRTOS mutexes for synchronization:

• inverterMutex — Protects access to the inverter state and control functions.
• measurementinMutex — Protects shared input measurement buffer.
• measurementoutMutex — Protects shared output measurement structures.
• measurementSpiMutex — Protects SPI-related measurement buffers and state.

Output Measurement (Output_meas.cpp)

Implements decimation, CIC filtering, RMS, and frequency analysis for AMC1306 bitstreams:

• buildByteCicLut() — Precomputes CIC integrator/differentiator contributions for all 8-bit patterns.
• OutputMeasurements() — Configures OSR, full-scale voltage, buffer sizes, and initial bit rate.
• init() — Allocates decimation ring buffers, analysis windows, and period buffers (with PSRAM support) and creates a snapshot mutex.
• copyRecentWindowWithStats() — Copies the newest segment from the decimation ring and computes mean, min, and max.
• findLastTwoRisingZcHyst() — Detects the last two rising zero-crossings with hysteresis to define one AC period.
• computeRmsOnePeriodExact() — Computes exact RMS over one period using piecewise linear interpolation.
• processRxBytesAndUpdateBitrate() — Processes raw SPI bytes, runs CIC pipeline, generates decimated voltage samples, and updates effective bit rate.
• analyzeStep() — Centers the signal, finds period boundaries, computes frequency, extracts a centered period, and calculates RMS.
• getSnapshot() — Returns the latest snapshot (RMS, frequency, period length) in a thread-safe way.
• copyLastPeriod() — Copies the last detected waveform period into a caller-provided buffer.
• copySinceSeq32() — Provides incremental decimated samples since a given sequence index, for streaming or plotting.

Emergency Stop (safety.cpp)

Implements minimal emergency-stop signaling for overcurrent events:

• g_emergency_stop — Global volatile flag indicating an active emergency stop condition.
• onAlertISR() — ISR that sets the emergency stop flag when the INA228 alert pin fires.

SPI Sampler (spi_sampler.cpp)

Implements DMA-driven SPI acquisition for dual AMC1306 isolated ADC channels:

• g_ch1_om / g_ch2_om — OutputMeasurements instances for both channels with hardware-specific scaling.
• g_sampler1 / g_sampler2 — Sampler context structures for SPI hosts, pins, DMA channels, and transactions.
• g_pack1 / g_pack2 — Pairs of sampler context and OutputMeasurements used by sampler tasks.
• spiSamplerInitMeasurements() — Initializes both OutputMeasurements engines and validates buffer allocation.
• spiInitAndStart() — Allocates DMA buffers, configures SPI bus and device, prepares transactions, and seeds the transaction queue.

Task Scheduler (Tasks.cpp)

Implements all FreeRTOS tasks for sampling, analysis, UI updates, control, and safety:

• spiSamplerTask() — Retrieves completed SPI DMA transactions, feeds data into OutputMeasurements, requeues transactions, and maintains sampling timing.
• analyzerTask() — Periodically calls analyzeStep() on a given OutputMeasurements instance to update RMS and frequency.
• printerTask() — Periodically prints analyzer timing, latest period samples, RMS, and frequency for both channels over serial.
• webSocketTask() — Processes WebSocket events in a loop to keep client connections responsive.
• webSocketUpdate() — Periodically collects input and output measurements and sends them as JSON via WebSocket to the UI.
• ControllerTask() — Runs the VRMS control loop by feeding the measured RMS value into the PI controller of the inverter.
• EmergencyStopTask() — Monitors the global emergency-stop flag, stops the inverter, signals the E-STOP output, and notifies the web UI when overcurrent is detected.

Webserver (webserver.cpp)

Implements Wi-Fi access point, HTTP endpoints, and WebSocket telemetry/UI control:

• resetDefaults() — Resets VRMS target and running state to their default values.
• initWiFi() — Starts the Wi-Fi SoftAP for the H-Bridge control interface.
• initServer() — Mounts LittleFS, serves static /index.html, /style.css, /script.js, and defines /start, /stop, and /ack-trip endpoints.
• updateMeasurements() — Packs input/output data and frequency into JSON and broadcasts it over WebSocket.
• broadcastStatus() — Sends current inverter running state to all connected clients via WebSocket.
• onWebSocketEvent() — Handles client connect/disconnect events and sends initial status on connect.
• broadcastTrip() — Notifies all clients of a trip condition and updates running state.
• _VRMS / _isRunning — Static internal state for desired RMS value and inverter run/stop status.

HTTP Endpoints:

• / – Main HTML page
• /start – Start inverter
• /stop – Stop inverter
• /update – Update VRMS target
• /bipolar.png – Waveform reference

Overcurrent Protection

Overcurrent protection is implemented through the INA228 fault pin:

1. When a current threshold is exceeded, drivers are disabled immediately.
2. A fault message is sent to the web interface.
3. After user acknowledgment, the inverter can be restarted safely.

Safety

• Use current-limited power supplies during development.
• Verify MOSFET temperature and load ratings.
• For educational/laboratory use only.

License

Released for educational and research purposes.
Use responsibly.