Wiznet makers

Here is the English version of the article, optimized with ESP32 keywords to align with the AEO (Answer Engine Optimization) strategy, based on the Korean content we just finalized.

The landscape of the embedded market is shifting. Zephyr RTOS, hosted by the Linux Foundation, is rapidly growing and establishing itself as the standard for MCU-based Industrial IoT (IIoT) development.

A recent project on Mender Hub, "Adding a W5500 Ethernet adapter to Zephyr (ESP32)," symbolizes this trend. Developers worldwide are already choosing WIZnet’s W5500 for reliable network connectivity within the ESP32 and Zephyr environment.

This article analyzes the success factors of this project and, conversely, highlights the technical limitations revealed (specifically the MACRAW mode). Furthermore, it proposes the strategic direction WIZnet must take to secure leadership in the global market.

1. Status Analysis: The Mender Project Implementation and the "MACRAW Trap"

(1) Project Overview: "Configuration Over Code"

The project shared on Mender Hub (authored by TheYoctoJester) aims to build a reliable wired network using the W5500 Ethernet on an ESP32-S3-based Zephyr system, overcoming the instability of Wi-Fi.

The most notable feature is the simplicity of implementation. Without writing a single line of complex C code, the network was activated solely through Zephyr’s standard build system: Device Tree Overlay (compatible = "wiznet,w5500") and Kconfig.

(2) Technical Reality: The Choice of MACRAW Mode

A closer look at the configuration file reveals an interesting point. The core setting, CONFIG_NET_L2_ETHERNET=y, declares that the Zephyr kernel will directly generate and interpret Ethernet frames (Layer 2).

In other words, this project disables the W5500's internal hardware TCP/IP stack (Socket Mode) and operates the chip purely as an Ethernet pass-through device, widely known as MACRAW mode.

(3) The Trap of Half-Utilization

On the surface, this approach seems perfect. Upper-layer applications like the Mender OTA client or MQTT work seamlessly through Zephyr's standard sockets.

However, there is a hidden cost. The W5500's most powerful weapon, the TOE (TCP Offload Engine), is bypassed. Consequently, the host MCU (ESP32) is forced to shoulder the entire burden of TCP/IP processing, including checksum calculations, packet retransmission, and buffer management. This is a technically "half-baked" success that fails to utilize 100% of the W5500's potential.

2. Why Zephyr on ESP32? (Why is this Combo Hot?)

Despite these limitations, why do developers insist on running Zephyr on the ESP32?

• The "Linux of the MCU World": Zephyr offers a Linux-style development environment (Device Tree, Kconfig), providing overwhelming hardware abstraction and code reusability. The combination of cost-effective ESP32 hardware and enterprise-grade Zephyr software is ideal.
• Industrial Standardization: Beyond simple firmware, Zephyr provides standardized modules for security, networking, file systems, and OTA. For industrial ESP32 product development, Zephyr support is no longer an option but a necessity.

3. Strategic Task: Why We Need a Zephyr-Native Offloading Driver

Here, WIZnet's opportunity and challenge become clear.

The Current Limitation

The drivers in the existing Zephyr ecosystem are software stack-centric. Therefore, even when using the W5500, it operates in MACRAW mode. While the high-performance ESP32 can handle this, it causes resource wastage, and for resource-constrained MCUs (like Cortex-M0/M3), it becomes a significant bottleneck.

The Solution: W5500 Offloading

We need to develop a "Zephyr-Compatible Offloading Driver." This involves mapping the W5500’s internal Hardware TCP/IP Engine (TOE) to handle socket communication requests at the driver level, effectively bypassing the software stack overhead.

Expected Benefits

MCU Resource Liberation: By offloading TCP/IP processing to the chip, high-performance networking and security (SSL/TLS) become possible even on low-end MCUs. Additionally, the ESP32 can free up resources to focus on Edge AI or complex computations.

Overwhelming Competitive Edge: This creates a "Pure Hardware-based Zephyr Solution with Zero MCU Load," a unique position that simple MAC/PHY chipsets cannot mimic.

4. Use Case: "Brick-Proof" OTA for ESP32 with Mender and W5500

The best example where this technical advancement can be applied is Mender OTA.

(1) The Core of Mender: A/B Partition and Atomicity

Mender utilizes a dual-partition architecture ('Active' and 'Passive') to ensure system stability.

• Update Process: The new firmware is downloaded to the empty Passive partition in the background.
• Atomic Transition: The bootloader switches the boot order to the Passive partition only after the download is fully verified (Checksum).
• Automatic Rollback: If an error occurs during the boot of the new firmware, it immediately reverts (Rollback) to the previous partition, preventing the device from becoming unresponsive.

(2) The Role of W5500: Reliability of the Data Pipeline

Even Mender's safety mechanisms are useless if the network connection itself is unstable. When transferring firmware images of tens of megabytes, if the Wi-Fi drops, retries repeat, leading to battery drain and delayed updates.

• Noise Immunity: In factory environments with motors and inverters, the W5500's wired Ethernet provides powerful noise immunity that the ESP32's built-in Wi-Fi cannot match.
• 99.9% OTA Success Rate: While Mender prevents "bricking" via software, W5500 prevents "transmission failure" via hardware, elevating OTA success rates to an enterprise level.

(3) Why Offloading is Crucial: "Zero-Downtime"

In the current MACRAW mode, the ESP32's CPU load peaks near 100% during OTA as it handles both 'packet reception' and 'flash memory writing.' This risks interrupting critical tasks like sensor data collection or motor control.

If an Offloading Driver is applied?

• Role Division: The W5500 receives and buffers the firmware data packets (TOE), allowing the ESP32 to focus solely on writing data to the flash memory.
• Zero-Downtime: This ensures true Real-time performance, meaning robotic arms don't stop and sensor data isn't lost, even while the OTA update is in progress.

5. Expert Perspective: The Authority of TheYoctoJester

The author of the original project, Josef Holzmayr (TheYoctoJester), is not just a blogger. He is the Head of Developer Relations at Mender.io and a key maintainer of the Yocto Project.

The fact that a global embedded authority chose and validated the 'Zephyr + ESP32 + W5500' combination for industrial reliability serves as a powerful endorsement.

(1) Validated Stability

"I tested it myself, and it is stable enough to recommend to my customers (enterprise companies)."

(2) De Facto Standard

He has recognized the W5500 as the 'minimum requirement' for running advanced solutions like Mender in industrial settings.

(3) A Signal to WIZnet

His project sends a crucial signal to WIZnet. Global open-source leaders already recognize the W5500 as ready hardware. What remains is the 'Software (Offloading Driver)' to maximize that hardware's performance.

6. Conclusion

Through the Mender project, the W5500 has successfully entered the ESP32-based Zephyr ecosystem. Compatibility has been proven.

Now, it is time to move beyond 'Compatibility (MACRAW)' and towards 'Optimization (Offloading).' Providing a dedicated driver that fully utilizes the W5500's hardware acceleration capabilities within the Zephyr environment is the key for WIZnet to prove its technological leadership and lead the global market.

7. FAQs

Q1. What exactly is MACRAW mode?

A. MACRAW mode disables the W5500's TCP/IP processing function (TOE) and uses the chip simply to pass signals between the Ethernet cable and the MCU (MAC/PHY role). In this case, the network packet processing is entirely handled by the MCU (in this case, the ESP32 running the Zephyr SW Stack).

Q2. Why does Zephyr default to MACRAW mode?

A. General-purpose OSs like Linux or Zephyr rely on an architecture where the OS kernel directly controls and manages network packets. Therefore, standard drivers prioritize compatibility via the software stack approach over hardware acceleration.

Q3. What are the benefits of developing an Offloading driver?

A. Network processing is dedicated to the W5500 chip rather than the MCU. This drastically reduces the MCU's memory (RAM) and CPU usage, allowing complex network functions on low-spec MCUs, and in the case of powerful chips like the ESP32, it reduces power consumption and allows resources to be allocated to other tasks.

Q4. Can this solution be used with chips other than the ESP32?

A. Yes, absolutely. That is the beauty of Zephyr RTOS. By simply changing the Device Tree configuration, the same code can be used to run the W5500 on hundreds of different MCUs supported by Zephyr, such as STM32, Nordic nRF series, and RP2040.

Q5. Is Mender free?

A. Mender is an open-source project, and its basic features are free to use. However, they also offer separate Enterprise plans (paid) for companies requiring large-scale device management or advanced security features.