--- title: "W5500 Module TCP/IP Ethernet Module Compatible with WIZ820io RC5 Internet of Things Review" url: "https://maker.wiznet.io/bruno/projects/w5500-module-tcp-ip-ethernet-module-compatible-with-wiz820io-rc5-internet-of-things-review/" markdown_url: "https://maker.wiznet.io/bruno/projects/w5500-module-tcp-ip-ethernet-module-compatible-with-wiz820io-rc5-internet-of-things-review/md" type: "UCC: User Created Content" author: "Banggood Wizard Review" author_url: "https://www.youtube.com/watch?v=taxGCBBSYMk" editor: "WIZnet" editor_url: "https://maker.wiznet.io/" original_author: "Banggood Wizard Review" original_url: "https://www.youtube.com/watch?v=taxGCBBSYMk" published: "2024-08-22" language: "en" likes: 0 views: 1093 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # W5500 Module TCP/IP Ethernet Module Compatible with WIZ820io RC5 Internet of Things Review > W5500 Module TCP/IP Ethernet Module Compatible with WIZ820io RC5 Internet of Things Review Original author: Banggood Wizard Review (source: https://www.youtube.com/watch?v=taxGCBBSYMk) ## Article [Embedded media](https://www.youtube.com/embed/taxGCBBSYMk) ## Summary This article analyzes how the WIZnet W5500 Ethernet controller provides deterministic network behavior and long-term production stability in embedded systems. By offloading TCP/IP processing into dedicated hardware, W5500 reduces MCU RAM usage, protects RTOS scheduling predictability, and offers a stable Ethernet foundation suitable for industrial and long-lifecycle products. --- ## What the Project Does Many embedded designs treat networking as an add-on feature. In practice, the network stack directly affects: MCU RAM consumption Flash usage Interrupt load RTOS task scheduling Worst-case latency in control loops When using a software TCP/IP stack such as LwIP, packet reception triggers interrupts, buffer allocation (pbuf), protocol parsing, and context switching before the application layer is notified. In resource-constrained MCUs (Cortex-M0/M3 class), this can consume a significant portion of available RAM and introduce latency variance under burst traffic conditions. This analysis examines how W5500 changes that architectural model. --- ## Where WIZnet Fits The W5500 is a hardwired TCP/IP Ethernet controller with: Hardware TCP/UDP/IPv4 stack 8 independent hardware sockets 32 KB internal buffer memory SPI interface (up to 80 MHz) Complete TCP state machine implemented in silicon Instead of running LwIP or a similar stack on the MCU, the network protocol engine executes inside the W5500. ### Architectural Role In this structure: The MCU handles only SPI register access and payload read/write. The TCP state transitions (SYN, ACK, FIN, retransmission handling) occur inside the W5500 hardware state machine. Internal 32 KB SRAM buffers network packets without consuming MCU RAM. This separation provides two major engineering benefits: **MCU Resource Recovery** LwIP configurations using `TCP_WND = 4*MSS` with two active TCP sessions typically require multiple pbuf allocations, often exceeding 12 KB of MCU RAM depending on configuration. W5500 isolates packet buffers inside its dedicated internal memory, reducing MCU network RAM overhead to driver-level structures (<1 KB typical). **RTOS Scheduling Predictability** In software stacks, packet reception triggers ISR → stack processing → context switching → application callbacks. Under traffic bursts, this path can increase worst-case task latency. With W5500: Protocol processing occurs in hardware. The MCU can poll or service interrupts at controlled priority levels. Network bursts do not force deep stack execution on the MCU. This improves scheduling determinism in control-oriented embedded systems. --- ## Implementation Notes Below is a minimal integration example using the WIZnet ioLibrary. ### 1. SPI Interface Registration // Register SPI read/write callbacks reg_wizchip_spi_cbfunc(spi_read_byte, spi_write_byte); This connects the MCU’s SPI driver to the W5500 register interface. --- ### 2. Internal Buffer Allocation (No MCU RAM Used) // Allocate 4KB per socket (8 sockets total = 32KB internal SRAM) uint8_t socket_buf_size[8] = {4, 4, 4, 4, 4, 4, 4, 4}; wizchip_init(socket_buf_size, socket_buf_size); The 32 KB buffer resides inside the W5500, not in MCU memory. --- ### 3. Deterministic TCP Server Setup uint8_t sn = 0; // Open TCP socket on port 5000 if (socket(sn, Sn_MR_TCP, 5000, 0) == sn) { // Hardware TCP state machine handles handshake listen(sn); } At this stage: TCP handshake (SYN/ACK exchange) Retransmissions Connection state tracking are executed inside the W5500 hardware engine. The MCU only processes payload data when required. --- ## Practical Tips / Pitfalls **SPI Signal Integrity**: Use short traces and proper grounding for stable high-speed SPI communication. **Interrupt Priority Control**: In RTOS systems, assign moderate priority to W5500 interrupts to prevent control-loop starvation. **Buffer Allocation Strategy**: Allocate socket memory according to expected traffic patterns; not all sockets require equal memory. **Link Detection**: Always verify PHY link status during initialization to avoid blocking on disconnected cables. **Watchdog Integration**: If using long blocking socket loops, integrate watchdog resets carefully. **Static vs DHCP**: Industrial deployments often prefer static IP configuration for predictability. --- ## FAQ **Q: Why use W5500 instead of running LwIP on the MCU?** A: W5500 offloads TCP/IP processing into hardware, eliminating large RAM buffers and reducing CPU load. This improves RTOS scheduling predictability and frees MCU resources for application logic. **Q: How does W5500 connect to the MCU?** A: It connects via SPI (MISO, MOSI, SCK, CS). Only register-level SPI access is required; no software TCP/IP porting layer is needed. **Q: What role does W5500 play in this architecture?** A: It acts as a complete hardware network engine, managing TCP state transitions, retransmissions, and socket buffering independently of the MCU. **Q: What is the difference between W5500 and ENC28J60?** A: ENC28J60 provides only MAC+PHY functionality, requiring a software TCP/IP stack on the MCU. W5500 integrates the full TCP/IP stack in hardware, significantly reducing MCU resource usage. **Q: Is W5500 suitable for long-lifecycle industrial products?** A: W5500 has been in continuous production for over a decade and remains widely supported across multiple MCU platforms, making it appropriate for long-term embedded deployments. --- ## Source WIZnet W5500 Product Page: https://www.wiznet.io/product-item/w5500/ WIZnet ioLibrary: Related Technical Review Video: --- Source: https://maker.wiznet.io/bruno/projects/w5500-module-tcp-ip-ethernet-module-compatible-with-wiz820io-rc5-internet-of-things-review/