The goal of this project is to be able to display all the SAOs I collected at Supercon. I'm inspired by the SAO Wall at Supercon, but it's too big for my home and I want something more modular so I can fit it in various locations and expand as needed. I also didn't want to deal with batteries (replacing real ones, or permanently powering fake ones), so I wanted external power. I settled on a hexagon PCBA that has ports for 4 SAOs, and can be powered via USB-C connector providing 5V. And then, in order to provide the mechanical mounting solution, a 3D Printed frame to insert the PCBA into. The separate frame let me decouple solving mounting from solving the circuit. I originally considered directly mounting the PCBAs to each other and avoiding cables, but I didn't figure out a good connector to use, and didn't trust myself to line up all the connectors on all 6 faces of the hexagon correctly (to allow for custom tiling). USB-C with two-pass-through ports provides arbitrary daisy-chaining and arrangement. I'm hoping the design is flexible enough that people can make upgrades that are backwards compatible and there can be variants of the design that can be used together. I want others to be able to also display their SAOs at home, and I hope this can make that easier. I work primarily in software, so this was a fun electrical and mechanical design and manufacturing challenge.

Size and shape:

Hexagons are bestagons, and tile nicely with themselves. Tiling hexagons is also slightly more interesting than tiling squares. I made the PCBA 50mm to a side because it was a convenient round number, and approximately the size of the 2024 Supercon badge. The frame is 110mm to a side, because that provided enough room to hide even stiff USB cables inside without feeling too bad bending them to fit. 

Ports:

4 SAO ports because they can be spaced out across a single tile to provide room for larger SAOs, and 6 felt too crowded. 3 doesn't feel dense enough.

Power:

USB-C is popular, cables are easy to find, and USB power supplies are plentiful. Each board has resistors on the CC pins of one connector so a USB-PD supply will provide up to 3A, which should be plenty for even sizable displays. Onboard is a 3.3V regulator for the SAOs providing 0.5A, but a component swap can easily change that. The SAO 1.69bis spec says SAOs can draw up to 0.25A, but in my experience they mostly pull much less than that. So you can install up to two powerhungry SAOs on one board, or four normal ones.

Control:

I added pads for a Pi Pico W (1 or 2), and connected it to the I2C and GPIO ports for all the SAOs on the board. Additionally, one GPIO pin on the Pico is connected to the enable (well, !shutdown actually) pin of the 3.3V regulator so it can be turned off (but that's nominally pulled high). I also added a touch point on the front of the board that is connected to an ADC pin of the Pico so it could be used as an input. I figure a modified version of the 2024 badge firmware could be used at first, but I haven't invested in testing any of this yet because I primarily want power, and pads are cheap.

Manufacturing:

I wanted it hand-solderable without too much struggle, so I picked mostly 0805 components (based on my experience at the SMT challenge). The USB-C ports only expose the power and CC pins for easiest soldering. I printed the frame on a Prusa MK4S because that's what I have access to, but the design is simple so any printer with a large-enough bed should work. Printing it front-down requires only a minimum of support material that is mostly easy to remove by hand and minimal tools. The clips for connecting the frames together are also small and easy to print.

Mounting:

The PCBA press-fits tightly and securely into the frame, but can also be easily extracted. Because I'm not good at this, the PCBA is not a perfect hexagon (I grabbed the hexagon image from wikipedia and manually placed the lines on the board edge layer over it). However, it is close enough...