You've got a free Saturday, a Raspberry Pi Compute Module 5 sitting in a drawer, and a small robot or drone frame begging for a brain. The usual problem? The moment you bolt a CM5 onto a carrier board, your sleek module balloons into something three times the size. ARK Electronics' new "Just A Pi" board is the weekend fix for exactly that headache.
What the build looks like
Just A Pi mounts to the back of the Compute Module 5 and matches its footprint almost exactly. Glance at it from the front and you'd swear it was, well, just a Pi. Despite hiding behind the module, it packs a serious feature set aimed at robotics, drones, and autopilot rigs where every gram and millimeter counts. Instead of chunky RJ45 jacks and full-size headers, ARK swapped in the compact JST-GH and FFC connectors that pro robotics hardware actually uses.
Under the hood
There's a built-in Ethernet switch — a Microchip KSZ8794 driving two 10/100 Mbps ports over JST-GH rather than bulky sockets. You also get UART, SPI, PWM, and GPIO broken out across multiple JST-GH headers, plus a PCIe connector on the Raspberry Pi 5 pinout, dual MIPI CSI camera lanes, Micro HDMI, USB-C with USB 3.0, and a separate USB 2.0 port. Power comes in through a 6-pin Molex CLIK-Mate connector, and ARK suggests a 5 V supply rated for at least 2 A depending on what you hang off it.
The parts-and-cost reality
This isn't a $10 hack — Just A Pi runs $335 as a standalone carrier, or $475 bundled with a CM5 Lite, a 64 GB microSD card, and ARK's preconfigured software image. It's built for the CM5, with limited CM4 compatibility, and the microSD slot only works on Lite variants without onboard eMMC. So it's a weekend project for the serious builder, not a casual tinkerer — but if you're chasing a flight-ready compute stack that won't blow your weight budget, the math gets interesting fast.
Spend your Sunday on this
If you've been waiting for an excuse to drop a CM5 into a tight drone or rover chassis, this is it. Clear a weekend, map out your connector loom, and you'll have a compact, professional-grade compute platform wired up before Monday. The hardest part won't be the wiring — it'll be deciding what to build around it next.
Originally published on blog.circuit.rocks.
