This video presents a redesigned, all-surface-mount version of a custom-built 100-megabit Ethernet Protocol Decoder. The primary motivation for the update was to streamline manufacturing, allowing the boards to be ordered fully assembled. The hardware tool passively taps into an Ethernet line, converting packet data into a parallel format with marker signals, making it possible to trigger on and analyze network traffic in real-time using a standard oscilloscope or logic analyzer.
Key improvements in the new version include a switch to USBC for power, color-coded status LEDs, larger operator switches, and full 8-pin pass-through to support Power over Ethernet (PoE). The video demonstrates the decoder's utility for real-time debugging, such as correlating network packets with hardware chip-select signals to diagnose an elusive packet-loss issue caused by clock jitter—a task difficult to perform with software tools like Wireshark alone.
An Updated Ethernet Decoder for Real-Time Hardware Debugging
00:00:03 Introducing the Redesign: The video introduces a new, all-surface-mount version of a 100-megabit Ethernet protocol decoder, designed to simplify manufacturing by enabling automated assembly.
00:00:28 Hardware and Usability Improvements: The updated board features several modern enhancements, including a USBC power port (relocated for better cable management), larger switches replacing the previous DIP switch, and color-coded LEDs for at-a-glance status checks.
00:01:42 PoE Support and Robust Design: The decoder now passes all 8 pins of the RJ45 connection, allowing Power over Ethernet (PoE) devices to work through it. While using less durable surface-mount jacks, the PCB thoughtfully includes footprints for through-hole connectors as a robust repair option.
00:03:01 Core Functionality Explained: The device allows you to visualize Ethernet packets in real-time on a scope. It outputs marker signals to identify when a packet is active (yellow trace) and where specific bytes are (green trace), enabling triggering on events that are otherwise invisible in the complex Ethernet waveform.
00:05:04 Advanced Packet Analysis: The byte marker signal has multiple modes. It can identify the different fields of a packet (e.g., MAC address, IP data, UDP payload, CRC) or act as a simple byte counter, which is useful for verifying a correct logic analyzer setup.
00:06:08 A Real-World Bug Hunt: The creator provides a concrete example of the tool's value, showing how it helped him find a bug where a W5500 Ethernet chip was dropping 1% of packets due to clock jitter from a MEMS oscillator. The decoder made it possible to see the packet arriving without a corresponding hardware interrupt.
00:09:19 Why No Gigabit Version: A gigabit-compatible version is not practical, as the 125 MHz parallel data output would require a very expensive, high-speed logic analyzer. For most use cases, forcing a link to 100 Mbps for debugging is sufficient.
00:09:53 Availability: The new, redesigned Ethernet decoder is available to purchase from the product website, etherdcode.com.