Project Introduction

Soldered Electronics designs open-hardware boards for makers, students, and small hardware teams, including the NULA family of development boards. NULA Ethernet is the newest addition, built around WIZnet's W55RP20 to bring wired ethernet to the same footprint and workflow as the rest of the NULA line, without asking anyone to wire up a second chip.

The Challenge

Every RP2040 project that needed wired networking ran into the same wall: the RP2040 has no ethernet of its own, so you'd pair it with a separate W5500 breakout and wire the two together over SPI. That's two footprints, two power rails, and a connector between them that has to be routed correctly every time.

For a one-off project, that's an extra hour with a multimeter. For a product meant to ship, it's a bigger board, one more BOM line, and one more thing that can fail once it leaves the workshop.

Going wireless looks like the easy way around it, but wifi drops out in noisy industrial settings and plenty of networks won't let an unmanaged device join at all. NULA boards are built so that plugging one in is the whole story, with no extra parts to source and no wiring diagram to follow, and nothing on the market delivered wired ethernet on those terms. The RP2040 side of a project was always well covered; the ethernet side meant sourcing, wiring, and debugging a second chip.

What Soldered needed was a board with ethernet built in from the start rather than bolted onto an existing RP2040 layout, without giving up the battery power, storage, and Qwiic support already built into every other NULA board.

The Solution

NULA Ethernet is built around the WIZnet W55RP20, which puts a dual-core RP2040 and a hardwired W5500 ethernet controller in a single package. For makers and anyone prototyping a microcontroller project, that means wired ethernet without adding a second chip or wiring it in by hand.

The board carries everything else a maker expects from a NULA design: an RJ45 ethernet port, USB-C for programming and power, automatic switching to battery power, a microSD card slot for local storage, a Qwiic connector for plugging in I2C sensors without soldering, a status LED, a dedicated debug header, and reset/user buttons, with ethernet speed and duplex defaulting to auto-negotiation and configurable manually if a project needs it, and onboard LEDs showing link, speed, duplex, and activity at a glance.

NULA Ethernet is directly supported in Arduino and the Pico SDK, so makers can start writing networking code right away without installing anything extra.

Why W55RP20?

The W55RP20 collapses two footprints into one before a single trace gets routed, which means fewer components on the BOM and no SPI link between an MCU and an ethernet controller for the design to get wrong.

Because the W5500's TCP/IP stack runs in hardware inside that same package, the RP2040 cores never have to run a software network stack alongside the application code, so the chip handles the network layer while the application code gets full use of the CPU.

Compatibility with the existing RP2040 ecosystem was the other deciding factor: the W55RP20 fits closely enough into existing RP2040 tooling and pin conventions that Soldered could add NULA Ethernet support directly to the community-standard arduino-pico core instead of maintaining a separate fork. An RP2040 paired with a discrete W5500 breakout was on the table early on, but it meant a second chip, a second footprint, and an SPI interconnect that the integrated chip removes entirely.

The Results

NULA Ethernet was built with the wide RP2040 and Arduino community behind it, making it significantly easier to develop a microcontroller project that needs wired ethernet. Instead of sourcing, wiring, and debugging a separate network controller, makers get a board that handles the networking on its own, leaving more time for the actual project.