Greg Davill's GlassUnicorn — A Beautiful Bespoke Baby LED Cube!

Packing pixels into panels of pico proportions.

Tom Fleet
13 days agoLights / FPGAs / Hardware 101 / Displays

There are some people who pop up on my Twitter feed who are an absolute joy to follow.

They manage to somehow turn out a stream of beautifully documented engineering projects, that showcase not only their technical ability, but also their endless energy and enthusiasm.

One person you should definitely be following if you are not already, is Greg Davill. He produces some simply impressive hardware projects that are not only solidly designed but look the part to boot.

His projects are named from two randomly combined words, and his latest project, GlassUnicorn, is his take on the recent trend of LED panel cubes.

These have been popular builds as of late, thanks not only to the decline in price of the LED display panels, but also due to the successful funding of the IceBreaker crowdfunding campaign — which has put cheap, powerful FPGA boards in the hands of the masses.

Pixel Packed Panels of Pico Proportions

As most cube builds are based around LED panels sourced from digital signage applications, a lot of builds are using 4mm LED pitch panels, which offer a good balance of cube size, visual effect and cost.

You can get finer pixel pitch panels, at quite a price bump though. As they are still destined for signage applications, they don't get much physically smaller, instead, cramming many more pixels into a similar area, hence the higher cost.

Davill has designed his own LED panel PCB, to suit his needs, and it's fair to say that this would be a standalone project for most readers in itself! From the PCBNew Python script to place the parts on the board, to custom the artwork on the silkscreen layer, a huge amount of work has gone into these panels.

Did I mention that Davill also handpopulates his boards?

A Brainy Board in Beautiful Blue

Driving this amount of pixels at a rate that looks pleasing to the eye involves some serious data rates, and the brains of the Cube Controller board pack a pixel pushing punch from not only a Lattice iCE40UP5K FPGA, but also a Microchip SAM D51 Cortex-M4F+ MCU.

This is a capable combination that we've seen deployed together before, when Cabe Atwell took a look at the dadamachines doppler dev board, which would serve as a good place for anyone looking to explore this architecture.

Davill will be publishing the gory details of how the hardware operates, but in a nutshell, he's using the powerful SAM D51 to generate animation frames, and passing the serialized data to the FPGA, which handles passing it on to the panels in a format they will understand.

There are a few neat tricks he's using under to hood, and we're very much looking forward to reading the write-up when he publishes it!

Mechanics

Most of us choose to specialize in one area of engineering, but Davill has this project covered on all fronts, not least the machined aluminium framework that will hold all these PCBs together! While manufactured in China, the frame is again Davill's own design, and it beautifully rounds off the look of the cube with a truly professional feel.

Internally, the panels are all linked using some neat FPC "origami", which really reduces the internal wiring mess to something quite a bit more manageable!

Even the power source, two 18650 Lithium Ion cells, is neatly held in place with the aid of a 3D-printed mount.

Where to Next?

Well, from recent Twitter updates, it appears Davill is very close to finishing this beautiful cube. Most of the hardware is verified, and the remaining work looks to be more software than hardware, which is both a blessing and a curse. While we might not see as many board-level photos, we are going to be treated to the sight of this pretty little pico-cube punching well above its weight!

Oh, and let me leave you with this little triangular teaser. I can't wait to see where this is going!

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Tom Fleet
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