📠 Industrial UART & RS-485 Communication Guide

Master the "Swiss Army Knife" of embedded systems; UART protocol, along with TTL, RS-232, and RS-485 physical layers.

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📖 About the Project

UART (Universal Asynchronous Receiver-Transmitter) is the oldest yet most indispensable communication method in the embedded world. It is used everywhere, from reading data at 3.3V from a sensor to communicating over 1.2km via RS-485 in a factory.

This guide aims to teach not just how to write Serial.print("Hello World"), but also asynchronous timing, voltage levels, noise suppression, and industrial protocols (Modbus basics).

🎯 What You Will Learn

• 🔌 Critical differences between TTL, RS-232, and RS-485 (Why does the magic smoke come out?).
• ⏱️ Baud Rate Math: The 2% tolerance rule and timing drift.
• 🧠 ESP32 & FreeRTOS: Reading data without blocking the main loop (Non-blocking).
• 🕵️‍♂️ Reverse Engineering: Decoding unknown device speeds using a Logic Analyzer.

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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	Differences between TTL, RS-232, and RS-485. Voltage levels and wiring diagrams.
02	⏱️ Protocol Math	Start/Stop bits, Parity, Baud Rate calculations, and timing tolerances.
03	💻 Integration & Code	ESP32 Hardware Serial, Ring Buffer usage, and asynchronous reading with FreeRTOS Tasks.
04	🕵️‍♂️ Troubleshooting	Using a Logic Analyzer, analyzing "Garbage Data", and reverse engineering tips.

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🛠️ Hardware Requirements

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

• Microcontroller: ESP32 (Preferred) or Arduino.
• Converter: USB-TTL Converter (CP2102 or CH340).
• RS-485 Module: MAX485 or similar UART-to-RS485 converter.
• Analyzer (Optional): Logic Analyzer (Saleae Clone - 24MHz).

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⚡ Quick Start: Blocking vs Non-Blocking

In industrial coding, delay() and readStringUntil() (blocking codes) are forbidden. Here is the difference:

❌ The Amateur Approach (Blocking)

// Bad Code: Freezes the entire system until data arrives.
// If the sensor fails, the device locks up (Watchdog Reset).
void loop() {
    String data = Serial2.readStringUntil('\n');
    ProcessData(data);
}

✅ The Professional Approach (Async)

// Good Code: Pushes to buffer if data exists, otherwise does other tasks.
void loop() {
    while (Serial2.available()) {
        char inChar = (char)Serial2.read();
        if (inChar == '\n') {
            ProcessPacket(); // Packet complete
        } else {
            buffer[index++] = inChar; // Add to buffer
        }
    }
    // Processor is free here! Update screen, blink LED...
    DoOtherTasks();
}

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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. 🛠️}