Two tiny 10x10cm PCBs for keyboards

Did you know that the price of fabricating a PCB jumps at the magic threshold of a ten centimetres square? That seems to be especially true in the USA where hobbyists only use local firms for tiny prototypes, and otherwise import from China etc. You can currently get a set of five PCBs shipped from JLCPLC for only USD $5. As long as you're happy with tiny keyboards, that's incredibly cheap!

Bivvy16D (in red) and Bivouac34 (in green) PCBs

So, I ordered two designs in January - the Bivvy16D is a split keyboard with 15 or 16 keys and a 5-way navigation button on each half (so 30 to 32 normal keys in total), while the Bivouac34 is a monobody keyboard with a left and right PCB joined with a ribbon cable using "gold finger" edge connectors (with 32 to 34 keys in total). I want to make a tented keyboard with this.

Small girth 8 graphs for keyboard wiring

This post is a less interesting follow up to my recent catalogue of girth 6 graphs for keyboard wiring, which give 4-key roll over (4KRO). As explained in my first keyboard and Graph Theory blog post, the idea here is applying these graphs to the design of diode-free computer keyboards where the bipartite matrix becomes a sparse scanning matrix. Using a graph with girth 8 gives 6-key rollover (6KRO), high enough not to be a practical limitation, unless perhaps for stenography? Sadly from a mathematical point of view these are mostly subgraphs of the Tutte Coxetter Graph (aka the Tutte 8 Cage), the unique smallest trivalent graph of girth 8.