STM32 Ethernet Communication Tutorial using Wiznet W5500 Module

The article “Ethernet Communication using STM32 Microcontroller and Wiznet (Interrupt Mode)” from EmbeddedThere demonstrates how to build a TCP-based Ethernet communication system using the STM32F103C8T6 (Bluepill) and WIZnet W5500 Ethernet module.
The project focuses on implementing interrupt-driven TCP communication, leveraging the W5500’s hardware TCP/IP stack for non-blocking, efficient, and reliable data transfer.

Hardware Setup

• Microcontroller: STM32F103C8T6 (Bluepill)
• Ethernet Controller: WIZnet W5500
• Interface: SPI (PA4–PA7)
• Interrupt Pin: PB1 (Falling Edge)
• Reset Pin: PB0
• LED Indicator: PB9
• Power Supply: External 3.3V (recommended for W5500 stability)

This setup provides a simple yet effective hardware base for anyone looking to add wired Ethernet connectivity to embedded systems or IoT devices.

Project Workflow

• Create and configure the project using STM32CubeIDE
• Set up SPI1 and GPIO interrupt pin (PB1)
• Add the WIZnet driver library to the project
• Initialize and open a TCP server socket (default port 8080)
• Communicate with a PC client (e.g., using Hercules) over Ethernet

When a message “Hello” is received from the PC, the MCU toggles an LED and replies with a confirmation message — “Received from [socket]”.
This simple interaction effectively demonstrates how STM32 communicates through the W5500 hardware stack.

Software Architecture

• W5500Init()
  • Registers SPI and control callbacks
  • Performs hardware reset on the chip
  • Allocates internal buffer memory
  • Configures static network parameters (MAC, IP, gateway, subnet)
• W5500_Enable_Interrupts()
  • Enables global and socket-level interrupts
  • Monitors CON, DISCON, RECV, and TIMEOUT events for all sockets
• HAL_GPIO_EXTI_Callback()
  • Triggered when W5500 pulls the INT pin low
  • Calls W5500_InterruptHandler() to read and clear interrupt flags
• W5500_Handle_Events()
  • Iterates through sockets and checks event flags
  • Invokes the appropriate handler (handle_connection, handle_received, etc.)
  • Manages socket state transitions like reconnecting or closing
• main.c Loop
  • Periodically calls W5500_Handle_Events()
  • Detects “Hello” messages in the receive buffer, toggles the LED, and responds with acknowledgment

Key Features

• Interrupt-driven communication:
  Efficient event handling with low CPU usage compared to polling.
• Hardware TCP/IP processing:
  W5500 manages the entire network protocol stack internally, freeing MCU resources.
• STM32CubeIDE-based configuration:
  Clean setup for SPI, EXTI, and GPIO via CubeMX graphical interface.

Conclusion

This project serves as a practical introduction to Ethernet communication using STM32 and WIZnet’s W5500 in interrupt mode.
By offloading TCP/IP tasks to the W5500 chip, developers can achieve stable and responsive network communication even on resource-limited microcontrollers.

It’s an excellent starting point for embedded engineers building IoT or industrial Ethernet applications with STM32.

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