--- title: "Pico-LLDP" url: "https://maker.wiznet.io/Grace_Koo/projects/pico-lldp/" markdown_url: "https://maker.wiznet.io/Grace_Koo/projects/pico-lldp/md" type: "UCC: User Created Content" author: "gdludeke" author_url: "https://github.com/gdludeke/Pico-LLDP" editor: "WIZnet" editor_url: "https://maker.wiznet.io/" original_author: "gdludeke" original_url: "https://github.com/gdludeke/Pico-LLDP" published: "2026-06-19" language: "en" hardware: ["WIZnet W5500"] likes: 0 views: 220 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # Pico-LLDP > A portable cable tester using Pico W and W5500 MACRAW mode to capture LLDP frames and display connected switch info — manufacturer, port, and IP — on a 2×16 LCD Original author: gdludeke (source: https://github.com/gdludeke/Pico-LLDP) ## Components - **WIZnet W5500** x 1 ([docs](https://docs.wiznet.io/Product/Chip/Ethernet/W5500)) WIZnet parts: W5500 ([Datasheet](https://docs.wiznet.io/Product/Chip/Ethernet/W5500/datasheet?utm_source=maker&utm_medium=project&utm_campaign=w5500), [product hub](https://maker.wiznet.io/products/w5500/)) ## Article ## Plug In a Cable, Know Exactly Where It Goes — Pico W + W5500 LLDP Network Cable Tester > An open-source portable network diagnostic tool that connects a Raspberry Pi Pico W to a Waveshare Ethernet HAT (W5500), captures LLDP frames in real time, and displays the connected device's manufacturer, model, port, and IP address on a 2×16 LCD — all within 30 seconds of plugging in a cable. --- ### Background: The Cable Mystery It's a situation every network engineer knows. You pick up one of fifty patch cables and ask: which switch port does this go to? Without tooling, the answer means logging into a switch console, running `show lldp neighbors`, or unplugging cables one by one until the right port goes dark. - **LLDP (Link Layer Discovery Protocol)**, standardized as IEEE 802.1AB, was designed to solve exactly this. Most managed switches, routers, and servers periodically broadcast their hostname, port identifier, and management IP in LLDP frames — to anyone on the same physical link who's listening. - **Pico LLDP** is a handheld cable tester that listens for those frames. Plug in any cable connected to an LLDP-enabled device, and within 30 seconds the 2×16 LCD shows you exactly what's on the other end. --- ### WIZnet's Role: W5500 MACRAW Mode Is the Whole Point In this project, the WIZnet **W5500** is not just an Ethernet connection method — it's the component that makes the core functionality possible. #### Why W5500 Is the Right Choice LLDP frames cannot be received through a standard TCP/IP socket. LLDP operates below the IP layer, at **Layer 2 (Ethernet)**. To receive LLDP, you need raw access to Ethernet frames — a **MACRAW socket** that captures everything on the wire without filtering. W5500 supports this directly. By setting Socket 0 to MACRAW mode (`0x04`), the W5500 stores every incoming Ethernet frame in its RX buffer. The RP2040 reads frames over SPI and filters for the LLDP multicast MAC (`01:80:c2:00:00:0e`) and EtherType (`0x88CC`). ```python # Set W5500 Socket 0 to MACRAW mode write_socket_reg(socket=0, addr=SN_MR, data=0x04) # MACRAW mode write_socket_reg(socket=0, addr=SN_CR, data=0x01) # OPEN ``` This is not achievable with a software TCP/IP stack like LwIP, which operates above Layer 2 and has no raw frame access. W5500's hardware socket architecture makes MACRAW mode a first-class feature, leaving the RP2040 free for application logic. #### Pin Connection | Signal | Pico W GPIO | | --- | --- | | MISO | GP16 | | MOSI | GP19 | | SCK | GP18 | | CS | GP17 | | RST | GP20 | --- ### How It Works: From Raw Frame to LCD Display The system is organized in three clean layers: ![](https://maker.wiznet.io/upload/ckeditor5/617938213%5F1781874950%2Epng) #### LLDP TLV Parsing LLDP frames are structured as a sequence of TLV (Type-Length-Value) fields. The parser skips the 14-byte Ethernet header and processes TLVs sequentially: ```python # TLV header: upper 7 bits = Type, lower 9 bits = Length tlv_hdr = struct.unpack('>H', frame[pos:pos+2])[0] tlv_type = (tlv_hdr >> 9) & 0x7F tlv_len = tlv_hdr & 0x1FF ``` | TLV Type | Information Extracted | LCD Screen | | --- | --- | --- | | Type 1 | Chassis ID (MAC or IP) | — | | Type 2 | Port ID | Screen 2: `Prt:Gi1/0/24` | | Type 5 | System Name | Screen 2: `Dev:CORE-SW-01` | | Type 6 | System Description | Screen 1: manufacturer + model | | Type 8 | Management Address (IPv4) | Screen 3: `IP:192.168.1.1` | The System Description string is parsed for known vendor keywords — Cisco, Juniper, Arista, HPE, Dell, Fortinet, Ubiquiti, Meraki, and more — to display a clean manufacturer name rather than a raw description string. #### LCD Display Cycle ![](https://maker.wiznet.io/upload/ckeditor5/617938213%5F1781875286%2Epng) --- ### Why This Project Stands Out - **W5500 MACRAW mode in practice**: W5500 is widely known as a hardwired TCP/IP controller, but this project uses it below the IP layer in MACRAW mode — a technically distinct and uncommon application that demonstrates the chip's flexibility beyond standard socket use. - **A real network engineering tool**: Cable identification, port mapping, and connection verification are daily tasks for network engineers and IT teams. This project delivers a sub-$20 alternative to dedicated cable testers that cost hundreds of dollars. - **Self-contained MicroPython implementation**: W5500 driver, LLDP TLV parser, I2C LCD driver, and a hardware test script — all in pure MicroPython with no external library dependencies beyond what ships with the firmware. - **Battery-operable**: Drawing approximately 150mA, the device runs for around 65 hours on a 10,000mAh power bank connected to the Pico W's VSYS pin — a fully portable field tool. --- ### Use Cases - **Cable tracing**: Plug in an unlabeled cable and immediately see which switch and port it connects to — no console access needed - **Installation verification**: After wiring a new rack, confirm each cable landed on the correct switch port before sealing the patch panel - **Network documentation**: Walk the room systematically, record switch name + port + IP for each cable, and build an accurate network diagram - **Equipment relocation**: Before and after moving servers or devices, verify the switch and port assignment hasn't changed - **Protocol education**: A hands-on demonstration of how LLDP works at the frame level, with real output visible on a physical display --- ### Tech Stack Summary | Item | Details | | --- | --- | | **MCU** | Raspberry Pi Pico W (RP2040) | | **Ethernet Chip** | **WIZnet W5500** (Waveshare Ethernet HAT) | | **W5500 Key Mode** | MACRAW socket (Layer 2 raw frame capture) | | **W5500 Pins** | SPI0 (GP16/18/19), CS: GP17, RST: GP20 | | **Display** | 2×16 LCD, I2C (GP0 SDA, GP1 SCL) | | **Development** | MicroPython, Thonny IDE | | **Protocol** | LLDP (IEEE 802.1AB), EtherType 0x88CC | | **Vendor Detection** | Cisco, Juniper, Arista, HPE, Dell, Fortinet, Ubiquiti, Meraki, and more | | **Power** | USB or 5V power bank via VSYS, ~150mA | | **License** | MIT | --- ### FAQ **Q. W5500 is known as a hardwired TCP/IP chip — is it used differently here?** Yes. While W5500's hardwired TCP/IP stack is its signature feature, this project uses MACRAW mode instead. In MACRAW mode, W5500 bypasses the TCP/IP stack entirely and delivers raw Ethernet frames directly to the application. This is essential because LLDP operates at Layer 2, below IP — standard socket APIs simply can't reach it. **Q. Does the connected switch need to have LLDP enabled?** Yes. The remote device must be transmitting LLDP frames. Most managed switches support it: Cisco (`lldp run`), Juniper (`set protocols lldp interface all`), Linux (`apt install lldpd`). LLDP frames are sent every 30 seconds, so allow up to 35 seconds after plugging in the cable. **Q. Does this use the Pico W's built-in Wi-Fi?** No. The project relies entirely on the W5500 Ethernet HAT for wired Layer 2 frame capture. Wi-Fi operates at a completely different layer and cannot be used to receive raw Ethernet frames. **Q. What information can I get from a connected device?** Manufacturer (Cisco, Juniper, Arista, etc.), model number, system hostname, connected port identifier (e.g., Gi1/0/24, eth0), and management IPv4 address. Some devices may not populate all LLDP fields — missing IP is common for devices without a management interface. **Q. How long does the battery last?** At approximately 150mA draw, a 10,000mAh power bank provides roughly 65 hours of runtime. Connect 5V to the Pico W's VSYS pin for battery operation. --- > **Project Links** > > - GitHub: [gdludeke/Pico-LLDP](https://github.com/gdludeke/Pico-LLDP) > > - WIZnet W5500: https://docs.wiznet.io/Product/Chip/Ethernet/W5500 > > - Waveshare Ethernet HAT: https://www.waveshare.com/wiki/Pico-ETH-W5500 > > - LLDP Standard: IEEE 802.1AB --- Source: https://maker.wiznet.io/Grace_Koo/projects/pico-lldp/