Wiznet makers

* All images in this article were generated by Gemini.

ATXmega W5500 Module Project

An IoT-ready network data logger built with the ATXmega128A3U MCU and WIZnet W5500 Ethernet chip.
By utilizing the W5500’s hardware TCP/IP engine, the system delivers stable and efficient network connectivity even on a lightweight 8-bit MCU.

Project Overview

• Author: marek (marekw1986)
• Platform: ATXmega128A3U + WIZnet W5500
• Purpose: MQTT-based remote monitoring and data logging

Key Hardware Components

• MCU: ATXmega128A3U running at 32 MHz
• Ethernet: WIZnet W5500 (hardware TCP/IP stack)
• Storage: SD card with FatFS
• User I/O: 3 LEDs, 3 buttons
• UART Debug Output: 115200 baud
• Communication: SPI bus for both W5500 and SD card

The W5500’s dedicated TCP/IP offload engine enables reliable network operation without consuming MCU resources, making it ideal for ATXmega-class devices.

Development Environment

• IDE: MPLAB X
• Compiler: AVR-GCC
• Programmer: AVRISP mkII
• Flash command:

avrdude -p x128a3u -c avrispmkII -P usb -U flash:w:code.debug.elf

Core Features

1. Network Communication (via W5500)

• DHCP automatic IP assignment
• MQTT messaging
• SNTP time synchronization (hourly)

2. Data Storage

• FatFS-based SD card filesystem
• Automatic logging to test.txt every 10 seconds
• Local data backup even during network outages

3. System Management

• 200 ms watchdog timer for autonomous recovery
• RTC combined with SNTP for precise timestamps
• UART debug messages for diagnostics

4. User Interface

• LED indicators (1 s / 2 s / 4 s blink patterns)
• Three pull-up buttons for interaction

Project Highlights

• W5500 hardware TCP/IP stack minimizes MCU load
• Stable simultaneous operation of DHCP, MQTT, and SNTP
• Local SD card logging for long-term data retention
• Automatic time alignment through SNTP
• Robust long-term operation with watchdog and reconnect logic
• Modular source structure for easy maintenance

Possible Applications

• Ham Radio telemetry with MQTT forwarding
• IoT sensor nodes with local data backup
• Network event data loggers
• Industrial equipment monitoring

Conclusion

This project showcases how the ATXmega128A3U paired with the WIZnet W5500 can deliver a compact, reliable IoT data logging solution.
With MQTT connectivity, SNTP synchronization, SD card logging, and resilient system management, it is suitable for real-world embedded applications.
It also serves as an excellent reference design for developers exploring W5500-based IoT systems.