🚛 Industrial CAN Bus (TWAI) Communication Guide

Master the "Heavyweight Champion" of automotive and heavy industry; CAN Bus protocol, with deep dives into ESP32 TWAI hardware, hardware filtering, and OBD-II diagnostics.

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📖 About the Project

UART, I2C, or SPI are gentle protocols; they love clean desktop environments. CAN Bus (Controller Area Network) is like a battle tank. It is designed to work flawlessly amidst electric motor noise, high magnetic fields, and meters of cable mess.

This guide aims to teach the ESP32 TWAI (Two-Wire Automotive Interface) hardware, Mask/Code filtering logic, and Arbitration (Collision Avoidance) rules in great detail, without hiding behind simplified Arduino libraries.

🎯 What You Will Learn

• 🔌 Physical Layer: Why do we use an external Transceiver (SN65HVD230)?
• ⚖️ Arbitration: Why is data never lost if two devices talk simultaneously? (Democracy Logic).
• 🎭 Hardware Filter: How to capture only relevant messages without burdening the processor?
• 🚗 OBD-II Hack: How to read your car's engine RPM and speed?

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📚 Content Map

This guide consists of 4 main chapters taking you from zero to hero:

Chapter	Title	Summary
01	🔌 Physical Layer	TWAI vs CAN difference, Dominant/Recessive voltages, and 120 Ohm termination resistor.
02	⚖️ Protocol & Arbitration	Message priorities, ID structure, and "Non-Destructive Arbitration" mechanism.
03	💻 Integration & Code	ESP32 TWAI driver setup, data queuing, and Mask/Code filters.
04	🕵️‍♂️ Error & OBD-II	Recovering from Bus Off errors and reading data from the vehicle diagnostic port (OBD-II).

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🛠️ Hardware Requirements

To practice the examples in this guide, the following hardware is recommended:

• Microcontroller: ESP32 (Contains internal TWAI controller).
• Transceiver: SN65HVD230 (3.3V compatible) or TJA1050 (5V - Requires Level Shifter).
• Cable: Twisted Pair cable.
• Resistor: 2x 120 Ohm resistors (For the start and end of the bus).

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⚡ Quick Start: Filtering Logic

The most confusing yet powerful part of CAN Bus is filtering. Here is how to say "Accept only IDs starting with 0x100":

// 1. Configuration
twai_general_config_t g_config = TWAI_GENERAL_CONFIG_DEFAULT(GPIO_NUM_21, GPIO_NUM_22, TWAI_MODE_NORMAL);
twai_timing_config_t t_config = TWAI_TIMING_CONFIG_500KBITS();

// 2. Filter: Accept only range 0x100 - 0x10F
// Code: Ideal ID, Mask: Don't Care Bits (1 = Ignore)
twai_filter_config_t f_config = {
    .acceptance_code = (0x100 << 21), 
    .acceptance_mask = ~(0xF << 21),
    .single_filter = true
};

// 3. Start
twai_driver_install(&g_config, &t_config, &f_config);
twai_start();

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🤝 Contributing

Did you spot a mistake or want to add some "Field Experience"?

1. Fork this repo.
2. Make your fix.
3. Submit a Pull Request.

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📄 License

This project is open-source under the MIT License. Knowledge grows as it is shared.

_{Written with battle scars. 🛠️}