“Raspberry Pi Pico has a lot of interesting and unique features, but it doesn’t have networking. Of course this was only ever going to be a temporary inconvenience, and sure enough, over Pi Day weekend we saw both USB Ethernet and Ethernet PHY support released for Pico and RP2040.
The PHY support was put together by Sandeep Mistry, well known as the author of the noble and bleno Node.js libraries, as well as the Arduino LoRa library, amongst others. Built around the lwIP stack, it leverages the PIO, DMA, and dual-core capabilities of RP2040 to create an Ethernet MAC stack in software. The project currently supports RMII-based Ethernet PHY modules like the Microchip LAN8720.
Breakout boards for the LAN8720 can be found on AliExpress for around $1.50. If you want to pick one up next day on Amazon you should be prepared to pay somewhat more, especially if you want Amazon Prime delivery, although they can still be found fairly cheaply if you’re prepared to wait a while.
What this means is that you can now connect your $4 microcontroller to an Ethernet breakout costing less than $2 and connect it to the internet.”