Debugging Like a Pro: Using JTAG, SWD, and Serial Debugging for Embedded Systems

Introduction

Debugging is a critical skill in embedded systems development. Whether you’re working with microcontrollers or complex SoCs, efficient debugging can save hours of frustration. This blog explores three essential debugging techniques: JTAG, SWD, and Serial Debugging, with hands-on examples to help you debug like a pro.

SWD (Serial Wire Debug)

SWD is an ARM-specific alternative to JTAG, using fewer pins while providing similar debugging features.

Key Benefits:

• Uses only two wires (SWDIO, SWCLK), reducing PCB complexity.
• Faster and more efficient than JTAG for ARM Cortex-M devices.
• Supported by tools like ST-Link, J-Link, and CMSIS-DAP.

Example: Flashing Firmware via SWD (STM32)

This command loads firmware onto an STM32 microcontroller using ST-Link over SWD.

Serial Debugging (UART Logging)

Serial debugging via UART is a simple and effective way to monitor real-time data and diagnose issues.

Advantages:

• Works on nearly all microcontrollers.
• Useful for debugging sensor data, error messages, and execution flow.
• Requires minimal hardware (TX/RX pins, USB-to-Serial adapter).

Example: Sending Debug Messages Over UART (Arduino)

This prints sensor values to the serial monitor, helping track system behavior.

Best Practices for Efficient Debugging

1. Use Debugging Tools Together: Combine JTAG/SWD for step debugging with UART for runtime monitoring.
2. Optimize Debugging Code: Keep logging minimal in production firmware to save CPU cycles.
3. Understand Peripheral Debugging: Use logic analyzers and oscilloscopes alongside software debugging tools.
4. Leverage Breakpoints & Watchpoints: Set strategic breakpoints in GDB/OpenOCD for efficient debugging.

Conclusion

Mastering debugging techniques like JTAG, SWD, and Serial Debugging will significantly improve your embedded development workflow. Use JTAG/SWD for deep-level debugging and firmware flashing, and rely on serial debugging for quick runtime analysis. Stay tuned for more expert embedded debugging insights!

Learn how to apply these techniques on real development boards by enrolling in our embedded systems course, designed for practical, industry-ready skill building.