Piunora Packs a Raspberry Pi CM4 Into a More Maker-Friendly Format You Might Be Familiar With!

Timonsku's Piunora puts a Compute Module 4 into the Arduino R3 form factor — opening up a whole new world of hardware hackability!

We knew that back in October of this year — less than a mere three months ago — that the release of the new Raspberry Pi CM4 module was going to make waves in the maker world.

This tiny little SoM — while really, not much more than a Broadcom breakout board — has given makers the ability to pack a 64-bit, quad-core Arm Cortex-A72 along with a few Gb of RAM, globules eMMC — if you want it — and about a gazillion I/O interfaces (give or take) into almost anywhere that you could fit a half-folded playing card.

Being an SoM, this product is targeted at being integrated into a base board or some sorts — in order to bring out the best (and bits and bytes) in it.

While this is new kit, and despite how busy the Raspberry Pi team has been recently, it would be silly to even feign surprise at the fact the Foundation was ready from day dot, with their design for a complete CM4 carrier board ready for you to cop at the same time as checking out your CM4 from the shopping cart.

And there it sits, glorious, grandeur, and well, giant. Rightfully so mind, it's a board designed to demonstrate getting from a bootstrapped "blinkenlights," to booting a blazing fast, dual HDMI desktop, with a PCIe interface sat freely available, and absolutely everything in between.

Likely designed in parallel, alongside the CM4, it would be silly to think that we'd see a new Pi SoM with no support efforts.

That's what a reference board is meant to do — support the entire possible operation of the product, perfect if you're going to squeeze every single bit or byte of performance out of this part, then fair play.

The thing is, and I submit this theory with the utmost sincerity and respect for us all, most makers are realistically not going to do that.

To us, the Pi is — and always has been — a brilliant platform that gives us a huge safety net in terms of application head room.

It's the little board that can do, even if it doesn't always need to.

Wandering along that line of thinking somewhere in the hardware world, we encounter the latest release from @Timonsku, with Piunora: his take on the CM4 carrier that more reasonably represents the requirements of the maker market.

Looking like a polished, professional product, we have to make the distinction that despite the ever growing photo-realistic render game we're seeing these days, this isn't ray-traced. Nor is it cake.

No, this is a fully-assembled homebrew effort in response to the CM4 that boots the little Broadcom SoM — designed and manufactured in less than three months.

Speaking with Timon, it sounds like most of that was in the conceptualization — the suggestion that most of the actual design and layout work probably took a few days is simply incredible to muse upon, given the outcome.

Less than a week from library creation to layout of a fully-functional Linux SBC carrier.

Despite the simplicity in mind when the SoM designers laid out the lines to the headers that help fan out the I/O of the CM4, this sort of turnaround time is frankly ridiculous for a product that is still arguably far more complex a design than the Arduino form factor it emulates.

We're going to pick this apart visually, as the repo isn't yet live, but let's break it down on this breakout board.

First up, let's analyze the atypical differences in design.

If we zoom right on up into the lower right-hand corner of the board, we spot an SOIC-16 IC snuck into to header that would normally handle the analog capable I/O of the processor sitting on such an R3 layout board.

We say normally, and in fact, this is still the case. In a bit of clever thinking, @TimonSKU has seen to it that this SoM shape-shifter can still wax lyrical with analog based accessories, with the inclusion of a Microchip MCP3008 — a 10-bit, 200kSPS, 8-channel ADC — the SPI interface means it is completely capable when it comes to providing a clean way to give that backwards-compatible, analog functionality.

Sat above the MCP3008, the microSD card socket sits in a sensibly opposed location to the majority of the "bulky" I/O connectors — by which I mean HDMI / USB cables. It's a simple thing to note, but it will put less strain on the connectors when swapping out SD cards, should any remain attached.

Light 'em up!

LEDs... we love LEDs, and luckily for me, there are a more than a few of my favorite devices to be found on this board for me to feature here!

There are the recognizable, invaluable status and power LEDs that solve so many boot issues that can be found with a botched config or corrupt SD card.

But hidden away amongst the bevvy of off-board connectors, sat betwixt the beefy ol' full size USB-A and conventionally sized HDMI port — hoorah! — lay a litany of LEDs, some dinky little DotStar Micro (AKA the APA102-2020 serial RGB LEDs).

With this colorful chaser being driven from CircuitPython, running on the CM4, it's becoming clear that this board is going to allow for some wonderful combinations of code and hardware, at varying levels of complexity.

Speaking of CircuitPython, let's take some time to point out the Qwiic port neatly placed, enabling compatibility with the huge range of boards — both Qwiic and Adafruit STEMMA — that make use of this off-board I2C connector.

There's more M.2 this than meets the eye...

If the dazzling array of DotStar Micro LEDs didn't already indicate this board might have a few more tricks hidden away, we'd be fools not to flip it over and see if we can't find a few more features we can focus in on.

Simple SD sockets out of the way, looking at this board from the other angle, we can see that the backside of this board boasts a M.2 card-edge socket, opening up compatibility with any such module to make use of the B-key variant of the M.2 connector.

With the PCIe signals pinned out here, this opens up the potential for super fast SSD storage expansion, or any sort of peripheral that you fit in place.

The additional USB-C connector, intended to act as a supplementary power input for any particularly power hungry parts connected on the M.2 interface.

It's not going to need that extra power input, but we can see a Google Coral AI accelerator card loaded up in the shot above — oh the possibilities!

But, does it boot?!

The question that is on everyone's mind when bringing up a new project — is it going to boot, or is that burning sense of anticipation going to result in a more literal sense of a smell of burning, from a bridged solder connection or such...

The proof is in the pudding, and with this Raspberry Pi proudly presenting the login prompt over HDMI, I'd say this pudding tastes pretty damn good!

Timon plans to certify this as OSHW-qualified hardware, so proper testing is important before the release of the design files — so if you're wanting to get your hands on this hot cake, sorry, you're gonna have to hold tight for just a little while.

Tom Fleet
Hi, I'm Tom! I create content for Hackster News, allowing us to showcase your latest and greatest projects for the world to see!
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