This Bit of Fluff Is Doing Anything But Sitting Gathering Dust!

Radomir Dopieralski's fantastic bit of Fluff (M0) is back in our sights, and this time, it's a family affair.

Tom Fleet
4 years agoHW101

As a writer, it's not all too often that you get to revisit a fluff piece. And even less are the odds that your topic for doing so is... well, a bit of fluff!

Radomir Dopieralski — aka @de∫hipu — is back at it again however, with his aptly named barebones SAM D21-based breakout board, called Fluff, and this time, we're taking a quick look at versions 1.4 onwards. Yup, Dopieralski is rolling fast with this one, with each uprevision bringing more and more to a project, where the goal is to do so with as little as possible.

Last time we saw Fluff, it was sat at v1.0, and by the time we leave here today, we'll be looking at v1.5. That's a fair amount as far as revision numbers go, and they are not without reason — so it's worth us taking some time to look through the family history here.

v1.0, peppered like it was plagued by the very same Propioni bacterium that results in the holiest of cheeses (Swiss Emmental, of course), was where we left off last time, and as nice as this board was, it might have had slight issue, in that the pins mappings for SCK and MOSI lines were... well, swapped at the PTH pads.

As flexible as the pin peripheral mapping of the SAM D21 is —and it's pretty forgiving — the SERCOM object IO can only be configured in one of a certain number of permutations, and swapping these two pins, unfortunately, would leave all SPI traffic on this board having to be bit-banged. Not ideal, so on to v1.2, which corrects the pinning and adds a CircuitPython definition that represents the correct pinning!

Personally, with boards looking this good in OSH Park After Dark, many of use might have left it here, calling it a project well produced.

Testing, testing, v1.1... v1.2... v1.3...

v1.3, shown above, looses its holy nature, and tries out something we have rarely seen put into practice before — for USB-C at least — an in-board paddle connector that is able to take advantage of the geometry of a USB-C socket, noting that the contacts are still made via a central paddle.

The 0.6mm PCB stack that was being used for Fluff is almost perfect to fit inside the USB C-plug, as a makeshift connector. It's a bold move — not something I would push to a consumer product, but for the application of a cheap, leave-in-place board that only needs to be programmed once or twice, it's a valid exercise into cost reduction and BoM optimization!

Just make sure you spec all the nets needed when negotiating a new connection, especially one with as many housekeeping features as USB-C. We'll touch on that later...

Moving ever forward, eyes on v1.4!

v1.4 looks like a bit of an optical illusion, and I love it. With homage paid to former holes d'fromage, a black silk screen traces the outlines of the contours omitted from the current design.

But less can be much more, and although the board has lost a few holes here and there, it's gained the missing area back, in the form of a neatly arranged peppering of PTH vias, packing 66 physical points into the same space, ready for you to place your parts and mods into.

It's an efficient use of space, and looks very, veryeye catching when seen on a suitably dark background, as seen above. Who says project boards need be boring?!

Further feature enhancements for the fourth of the Fluff family include the addition of the crucial contacts required to communicate on the CC lines of USB-C, with pads and pull-down resistors in place as required, allowing the board to request power from USB-C ports directly, rather than relying upon questionable cables and adaptors to do the CC line strapping as specified.

The... 5th time's the charm?

I'm not throwing shade at the predecessors to this pentagonal series of prototyping boards, but I can't leave this lineage of lightweight SAM D21 development boards incomplete — and let v1.5 sail by without a cursory eye.

At some point, someone has thrown the phrase "peppered like swiss cheese" at Dopieralski, and they have taken it to heart.

With even more prototyping holes poked in place, and a lively red solder mask finish, that may or may not be in a similar livery to a certain... well known... manufacturer of folding knives... (careful with the trademarks now...), the finish of this little bit of fluff looks phenomenal!

There's a slight change, beyond the fantastic red finish though, and it's not immediately obvious from the render. That is, until you flip over to the other side of the board, and focus in on that nifty in-situ USB-C connector... that is now not quite so USB-C looking...

Having perhaps realized that USB-C is overkill for a low-cost dev board like this, not only in data rates, but also manufacturing tolerances and indeed interface support components — the idea has been rolled back to a similar selection of pads and PCB protrusions, that instead targets the family favorite; our old friend USB Micro-B!

Prototyping is a process with multiple stages to it — and this family of Fluff boards is a beautiful illustration of the processes of design and deliberation that go into a well-rounded, design optimized development board.

I suggest you check out the full write up from over on HaD for a deep dive into more of the design choices made by @de∫hipu, and be sure to check him out over on his site for more content along this thread.

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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