32 keys good, 30 keys better?

I designed my Goldilocks32 keyboard for either 32 or 30 keys, and for the last three months or so have been using it (still without a case) as my daily driver in 30 key mode. During that time I have finished and built a related 30 key design, my Rugby Union Keyboard (so named because it has 15 keys a-side).

The build was a lot harder than I expected!

Naturally it is diode-free with a Graph Theory based sparse scanning matrix to avoid ghosting. This time I'm using the Subdivided Petersen Graph with 25 edges (10 columns of 3 keys, and 15 scanning rows of 2 each) for 30 edges or keys. This graph is girth 10, meaning 8KRO - to me a natural progression from using girth 6, then girth 8, only made practical by moving to a smaller keyboard. The PCB silk screen art features the Petersen Graph (as a pentagram inside a pentagon).

On the hardware side this again uses an RP2040 Pro Micro (with 25 easily accessed GPIO pins) and a reversible twin PCB, with the exact same key placement. What is new is the idea of joining the two PCBs using header pins - which turned out to be too rigid. Instead I had to solder 16 short softer connecting wires.

Frustratingly those 16 wires have to be long enough otherwise the PCBs do not lie flat in the case. This makes the build much trickier than using a gold finger edge connection and a ribbon cable! I don't intend to use this approach again.

And this time I did design a case! This was printed in Tinmorry Galaxy Green PLA by a friend at the Dundee MakerSpace, and turned out beautifully. 

The other disappointment was those nice white store-bought sculpted KLP Lamé keycaps (see first photo) are a fraction wider than the ones I had 3D printed and am using on the Goldilocks32 - just enough to jam with the tight 16.5mm vertical spacing here. I had a fall back, I had just enough surviving 3D printed Chicago Stenographer keycaps to test out the Rugby Union:

The good news is those keycaps worked. The bad news, the first build won't quite close at the back (photo not shown). My connecting wires are a fraction too short, and/or the case too wide. A slight case revision is in progress which also improves the USB port placement and gives a fraction more room on the corner and thumb keys

And some more frustrating result: the angles didn't immediately feel quiet right on my desk, nor on my under-desk pull out keyboard tray. It actually felt better on my lap. I need to try it on the kitchen table with my laptop maybe?

Where next?

I already have a follow-up design, using the same basic layout but with different angles drawing heavily on the Leonardo-KeycapRio keyboard by using a single PCB and swan-neck bends too allow it to be bent... the PCB for my Wee Bit Warped (30 keys) keyboard has just arrived! This has conventional 17mm vertical spacing so my new keycaps should fit this time. Further updates to follow...