My first post about keyboards introduced the idea of Graph Theory applied to keyboard wiring. I have since used the girth 8 Tutte-Coxeter Graph to build a 6KRO keyboard (the Gamma Omega TC36K), and several girth 6 graphs to build 4KRO keyboards (see table of girth 6 graphs for keyboards in this recent post). But what about other kinds of switches like 3-way jog dials (up/down/push) or 5-way directional buttons (up/down/left/right/push)?
I did a retrospective in August of how looking for a replacement keyboard led up to building a Ergonomic Mechanical Keyboard with a self-designed PCB roughly six month later (the diode-free Graph Theory based Gamma Omega TC36K). That design is beginner friendly, and went smoothly. In October someone else made a pair of them - nice!
 |
| A pair of Gamma Omega TC36K keyboards |
Up until now, I have had three different keyboard PCBs fabricated to my own design - all diode-free using Graph Theory. The Gamma Omega TC36K, the Gamma Omega Hesse, and the Forager Acid, with 36, 36 and 34 keys respectively. They've been getting smaller. Well now for something bigger, requested by our nine year old: They want a keyboard with more keys, and deserve smaller keys. Here is the Slump52!
 |
| Slump52 keyboard PCB design in KiCad |
This post is an expanded and reworked version of the table in my first keyboards and Graph Theory blog post, listing the best (in terms of maximal number of edges) girth 6 bipartite small graph(s). I added many of these to the House of Graphs database, and then in October the mathematician Steven Van Overberghe added a few more. My interest here is applying the graphs to the design of diode-free computer keyboards where the bipartite matrix becomes a sparse scanning matrix, and girth 6 becomes 4-key rollover (4KRO).
My journey into the world of DIY Ergonomic Mechanical Keyboards began when my Microsoft Natural Ergonomic Keyboard 4000 started to fail. That has a very slight curve to the alphabet block's rows, which became more pronounced in later designs like the Microsoft Sculpt Ergonomic Keyboard (see Wikipedia). However, these all have the traditional row stagger which gives the right hand comfortable (diagonal) columns of keys per finger, but not the left.
In the DIY mechanical keyboard world column based layouts and orthonormal are popular (keys in a grid), but there is another solution which at first glance preserves the traditional row stagger: The symmetric katana stagger, originally popularised by Baris Tosun aka RominRonin's Kanata keyboards as early as 2015. Well, what if you combined that with a curve to each row?
 |
| This looks like a row stagger, but there are well defined columns for each finger! |
