---
title: "ONE MCU BY TWO SEPERETED SPI"
url: "https://maker.wiznet.io/forum/15611"
markdown_url: "https://maker.wiznet.io/forum/15611/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "bahmanroshan"
created: "2025-02-25T20:30:27+09:00"
last_activity: "2025-02-27T10:17:26+09:00"
language: "en"
views: 2
replies: 2
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# ONE MCU BY TWO SEPERETED SPI

## Question

Asked by bahmanroshan on 2025-02-25 in Ethernet Chips.

I Have One STM32 which Is Connected To The W5500 By Separated Dedicated Spi And GPIO Pin.

What Is The Best Manner Of C Coding For Handle This Four W5500 .

## Replies

### Reply 1 (verified answer) by WIZnet AI assistant (automated answer), 2025-02-25

To handle multiple W5500 chips with a single STM32 microcontroller, you need to manage the SPI communication and GPIO pins effectively. Here are some general guidelines for writing C code to handle four W5500 chips: 1. **Initialize SPI and GPIO:** - Set up the SPI interface on the STM32 to communicate with the W5500 chips. - Configure the GPIO pins for each W5500 chip, especially the Chip Select (CS) pins, which are crucial for selecting the active W5500 chip during communication. 2. **Chip Select Management:** - Use separate GPIO pins for the CS of each W5500 chip. - Before starting communication with a specific W5500, set its CS pin low and ensure all other CS pins are high to avoid conflicts. 3. **SPI Communication:** - Implement functions to send and receive data over SPI. These functions should handle the activation and deactivation of the CS pins. - Ensure that the SPI settings (such as clock polarity and phase) are compatible with the W5500 requirements. 4. **W5500 Initialization:** - Initialize each W5500 chip by configuring its registers. This includes setting up the network parameters like IP address, subnet mask, and gateway. - Use the SPI communication functions to write to the W5500 registers. 5. **Data Handling:** - Implement functions to handle data transmission and reception for each W5500. This includes managing the socket operations for TCP/UDP communication. - Use the W5500's internal memory efficiently to handle multiple sockets. 6. **Concurrency Management:** - If your application requires simultaneous communication with multiple W5500 chips, consider implementing a task scheduler or using interrupts to manage the communication efficiently. 7. **Error Handling:** - Implement error handling mechanisms to manage communication failures or unexpected behavior from the W5500 chips. 8. **Testing and Debugging:** - Test the communication with each W5500 chip individually before integrating all four. - Use debugging tools to monitor the SPI communication and ensure that the data is being transmitted and received correctly. By following these guidelines, you can effectively manage multiple W5500 chips with a single STM32 microcontroller. For more detailed information and code examples, you can refer to the technical documentation available at [docs.wiznet.io](https://docs.wiznet.io). If you have any specific questions or need further assistance, feel free to ask! WIZnet AI Support Team

### Reply 2 by louis_m, 2025-02-27 (in reply to reply 1)

You want to control four W5500s with one MCU, right?
With four SPI channels, you can.

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Source: https://maker.wiznet.io/forum/15611