MAC address scanner

A pocket tool that shows the MAC address of whatever Ethernet device it is plugged into, on an e-paper screen. No IP configuration, no DHCP, no PC — just plug in a cable and read the MAC off the display.

Hardware

• WIZnet W5500-EVB-Pico — RP2040 + W5500 Ethernet (SPI0, GP16–GP21)
• Waveshare Pico-ePaper-2.66 — 296×152 e-paper (SPI1, GP8–GP13)

The panel plugs straight onto the W5500-EVB-Pico's 40-pin header. The two devices use different pins, so there is no conflict:

Function	Bus	Pins
W5500 Ethernet	SPI0	MISO 16, CS 17, SCK 18, MOSI 19, RST 20, INT 21
e-Paper display	SPI1	DC 8, CS 9, SCK 10, MOSI 11, RST 12, BUSY 13

How it works

The W5500's socket 0 is put into MACRAW receive mode, so the chip delivers every raw Ethernet frame (it sees) on the link. The source MAC field of each frame is the hardware address of the device that transmitted it. On a direct point-to-point link that is exactly the device you plugged into. The most recently seen MACs are drawn on the e-paper.

It is entirely passive — it relies on the peer transmitting something (ARP, STP, LLDP, DHCP, IPv6 neighbour discovery, mDNS, …), which essentially every networked device does within a few seconds of link-up.

Note: If you plug into a switch rather than a single device, you may see broadcast/multicast and any traffic the switch actually forwards to this port, not just the switch.

Files

• main.py — application (capture loop + display)
• w5500_sniffer.py — minimal direct-SPI W5500 MACRAW driver
• epaper2in66.py — Waveshare 2.66" e-paper driver (vendored, MIT)
• selftest.py — hardware-free check of the MACRAW framing logic
• typings/ — MicroPython type stubs for the editor (not flashed to the board)
• pyrightconfig.json — points the type checker at typings/

Flashing

1. Install MicroPython on the W5500-EVB-Pico (the standard Raspberry Pi Pico RP2040 build works).
2. Copy main.py, w5500_sniffer.py, and epaper2in66.py to the board (e.g. with mpremote or Thonny). main.py runs on boot.
3. Plug an Ethernet cable from the tool into the device under test.

mpremote connect auto cp epaper2in66.py w5500_sniffer.py main.py :
mpremote connect auto run main.py

Testing

selftest.py runs the real read_frame() code path against an emulated W5500 on desktop Python — no board or network needed:

python3 selftest.py
# OK: recovered ['AA:BB:CC:DD:EE:01', '11:22:33:44:55:66']

Editor setup (type stubs)

MicroPython adds modules and functions that don't exist in desktop CPython (machine, framebuf, utime, and time.sleep_ms / ticks_ms / ticks_diff ...), so an editor's type checker flags them as unknown. The typings/ folder provides .pyi stubs for exactly those, and pyrightconfig.json tells the checker (Pyright / Pylance / basedpyright, as used by Zed and VS Code) where to find them:

{
  "stubPath": "typings",
  "typeCheckingMode": "basic",
  "reportMissingModuleSource": false
}

With this in place the project reports no import errors, and you get real autocomplete for Pin, SPI, and FrameBuffer. These files are editor-only -- do not copy typings/ or pyrightconfig.json to the board.

The stubs are board-independent, so you can drop the same typings/ folder and pyrightconfig.json into any MicroPython project. Only the four modules used here are covered; add more (network, rp2, neopixel, ...) as your code needs them.