This 6-inch board turns a Raspberry Pi module into a DIY router

Let your Pi do the work while the CM4 Router Board handles the connections.
Enlarge / Let your Pi do the work while the CM4 Router Board handles the connections.

If you’re intrigued by the prospect of building a DIY router, Seeed Studio has a board that’s just waiting to put a Raspberry Pi Computing Module 4 (CM4) to work. Assuming, of course, that you can find the Pi module.

Seeed’s CM4 Router Board adds two full-speed gigabit network ports, two USB 2.0 ports, a microSD slot, an HDMI out, a GPIO interface for Raspberry Pi HAT add-ons, and a 0.91-inch OLED display to your Pi CM4. Having the CM4 at the system’s core gives you 32 different options for RAM, storage, and wireless capabilities on your homebrew router. The Router Board comes with OpenWRT installed, but it could run Ubuntu, Raspberry OS, or any other Pi-friendly system.

Seeed notes that beyond DIY routers, the CM4 Router Board could also become a gateway, mini-NAS, wireless network bridge, or mini-server. You can buy a Pi CM4 with wireless capabilities, but you’ll likely need (or prefer) a separate Wi-Fi setup connected to your DIY router.

Why not just plug a USB-to-Ethernet adapter into the Pi you already have? Seeed says its board’s RTL8111E controller chip “offers better performance, lower CPU usage, and higher stability for a long time work [sic] compared with a USB network card.”

The CM4 Router Board should be available for around $55 soon at both Seeed and Mouser Electronics, though the latter cites an 11-week lead time beyond its initial stock.

Those hunting for a Raspberry Pi CM4 board might consider Ars commenter MightyPez’s advice to keep an eye on Pi stock monitor Rpilocator, which offers RSS feeds. You can even set up push notifications with Rpilocator’s official Python script.

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