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2025-09-10 | 12:44 (-07:00)

NOT MINE. I just think these are cool  :puppypleading: 

https://github.com/triliu/Heawood42 https://github.com/triliu/JESK56

Diodeless keyboard pcb designs requiring fewer pins than keys.  Leverages some
graph theory. 

What is the smallest graph with at least 18 edges and a girth of at least 6?
Not sure where to begin.  (This is not homework. it's for a keyboard).  I can
remove 1 vertex from the heawood graph to get a 13-vertex graph that satisfies
the constraint.  I don't know if there's smaller.

Edit: Pretty sure it's the smallest.


wait! it's not mine 😭 i should have clarified.  However, im looking at the
xiao nrf52840 plus and thinking about what could be achieved.  Or the just the
non-plus version, but 11 pins means 14 switches max per mcu, iirc.

Ah :P I recently assembled a DASBOB keyboard because I want to experiment with
less keys. At 36-keys, it's the least keys I've tried thus far. I'll be
relearning how to type, so this presents the opportunity to experiment with the
Hands Down layout(s).

Initially, I wanted to order the PCBs directly from a manufacturer or design my
own -- the latter to learn kicad -- since I wanted clear solder mask on black
FR4. I think seeing the traces is cool, and I like the look of copper on black
:3 However, price constraints lead me to just purchase some prefab PCBs.

I forgot what exactly lead me to the Heawood42 and JESK56.... I'm guessing that
I was yesterday wondering if diodeless is possible without having to resort to
1 pin per switch. The probable motivation: Pro Micro replacements tend to have
an amount of gpio pins that would limit the pre additional keyboard features
(display,  encoders,pointing devices, etc.) at around 36 keys or higher,
assuming a typical diodeless design. Why diodeless? I'm lazy and I dunno. I
think it's cool :laceshrug: After searching around (probably "diodeless more
keys per gpio" or something like that), I landed on a reddit post by trilliu.

Semi-concurrently, I was looking into Hands Down layouts and noticed that the
primary author currently uses ZMK. The 0xCB Helios controllers for my dasbob
are not compatible, so I looked into ZMK compatible boards and learned of the
Seed Studio XIAO platform. Ironically, if I ever do design a new keeb, ZMK and
the prospect of wireless would probably lead me to minimize feature set to
minimize power consumption and avoid having to mitigate firmware limitations. I
wondered about a smaller MCU enabling smaller keyboard form factor, but that
might sacrifice ergonomics, and I honestly mainly think using a smaller MCU
while leveraging graph theory is cool :blep:

I've not yet mentioned that I maybe want to make a reversible pcb design to cut
down on costs -- and, again, because it's cool ;P I know that cheaper MCUs
exist, but the XIAO nrf52840 Plus has an interesting set of 1.27mm pitch
castellations between 2.54mm pin headers that also have castellations. This
design seems mainly intended for SMD soldering, but it could be an interesting
challenge to make some kinda socketed/swappable solution without sacrificing on
gpio pin accessibility, especially if done without another PCB for more typical
header mounting. 

I actually don't know much, lol.  The dasbob I recently finished is my first
soldering project. I first learned how to desolder to remove a broken tft
display (from a tipsy badge I got at the defcon shoot this year). Then, I
soldered for the first time while assembling the dashob, lol.  As for keyboard
layouts, I'm just a qwerty person so far. Yet to settle on a layout to try.
I'll maybe go with Hands Down Promethium, but I need to think about what I want
to modify and how exactly to set up layers for my use cases.  Also gotta decide
whether to use stuff in the Hands Down repo or just stick with default QMK
features.  Oh, and hypothetically, diodeless 28-key is possible with the
non-Plus XIAO nrf52840 :cateyes: ...i might turn all that into a blog post on
my site. Got nothing rn :puppysob: :think:

2025-09-xx | xx:xx (-07:00)

#100DaysToOffload

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