2/25/2026 - Research

So basically my idea is to make a split keyboard that can combine to become a single standard keyboard. There are lots of row staggered gaming keyboards that do something like this, but they all have a cable that tethers the halves together even when 'combined'. Another issue with these is that they don't actually combine so you can't really grab the keyboard easily or have it in your lap.

My keyboard (I hope) will be able to mechanically combine the halves (hopefully mostly seamlessly (meaning basically there won't be any gap between the keycaps in the middle)) so that you can hold and use it as a single piece, or split it in half to use more comfortably if somewhere where you have enough space. (Because this isn't yet hard enough) the PCB will have an integrated MCU (to keep it super compact) and be reversible to reduce cost (since there is a 5 MOQ anyway). Also hotswap cuz why not (even more difficulty when routing).

Here are some things I decided on:

• MCU - STM32F072CBT6: LQFP-48_7x7mm pretty compact but still has all pins exposed so should be able to be hand soldered. Also has plenty of internal flash so I don't need many other components.
• Interconnect: It will use leaf spring contact thingys so that the halves can connect without being perfectly aligned or when used as a split board, I can have a side piece that slots on to cover the exposed inside and has a cable and contacts built in so that it automatically touches the springs. https://www.harwin.com/products/S1961-46R
• Reversible: To make it reversible I don't need any fancy footprints (other than for the switches) since I can just have a copy of each footprint on each side of the board and only populate the one that is on the bottom for each half. I am using almost all SMD parts to help with this but it will probably only be like 0805, maybe 0603 if I really need more space so it shouldn't be that hard to hand solder (the MCU is 0.5mm pitch but with solder paste it should still be hand solderable (USB C is about the same and it isn't that bad (FLUX FLUX FLUX fixes everything))).
• Layout: 6x3 + 4 key thumb row (per half so I guess more like what would be more like a regular 12x4 board. Also that means 44 keys so 40% board I guess?) ortholinear. This should make routing a bit easier since the rows + cols are straight lines.

The split/combined mechanical stuff should only really involve the case and a little bit of the interconnect. Right now I have a few different ideas on the mechanical part. My main one is to have removable side pieces on the case in the center so that the contacts can touch which can then be put into slots on the bottom of the board for storage/mechanically holding it together. I might try to find some way to securely hold those in place with screws with the folding tab grip thing like the ones on cameras and stuff or a sliding latch.

maybe something like this:

This is a lot of stuff that I want to add so I fully expect that some features will be dropped (most likely hotswap because the larger holes and pads take up quite a bit of space).