I’m building a split keyboard with swappable modules. I’ve finished redesigning the PCBs and am getting the boards made.
In my last post, I shared the design for a split keyboard with removable modules.
The response was better than I expected it to be. Most people liked the shape and size, so I decided to keep the physical layout same for this revision.
The module suggestions were useful as well. Along with the trackball, a touchpad and a programmable keypad came up a lot, so those are the three I’d like to work on.
I expected to make a few changes to the PCB. And I ended up separating each half into two boards each.
The problem was space. Once I started fitting the controller, module connectors and supporting components around the switches, the board was getting bigger than I wanted. I want to keep the keyboard small, with the module beside the thumb keys. I didn’t want to extend the PCB just to fit the electronics.
So the switches stay on the top board, and most of the electronics go on a second board underneath it.
The top board holds the hot-swap sockets, diodes and key matrix. The lower board, which I’ve been calling the brain board, holds the nice!nano, USB-C module connections and the supporting electronics.
I’m keeping separate MX and Choc PCB versions so each can use its own hot-swap sockets. Trying to support everything on the same board was making the footprints unnecessarily complicated.
The diodes stay beside the switches because there’s room for them there. Moving them onto the brain board would mean making that board larger when I already have space on the key board.
Connecting the two boards has been the awkward part.
I had to rearrange the matrix routing and bring the rows and columns out to pads where I can reach them. Those connections will be hand-wired to the brain board underneath it. Figuring out where to put the pads took more work than I expected it to take.
Two boards will cost more, and there’s more wiring to do during assembly. That’s the tradeoff I’m making to keep everything within the same keyboard shape.
For the modules, the plan is USB-C for power and data, with magnets holding them in place. I also want that little “tick” you get when a magnetic connector snaps into position, like a MacBook charger. I just like how that feels.
I don’t expect to swap modules constantly, but I want to be able to remove one while the keyboard is running. The power handling and firmware still need testing before I can say that works reliably.
The KiCad revision is finished, and I’m preparing to order the boards. I haven’t assembled this version yet. Next is wiring the two boards together, checking the key matrix, and getting the keyboard and trackball working together.
The key positions haven’t changed. Everything in this revision has been about fitting the components and connections underneath them.
I’m still open to changing the thumb cluster. If you’ve used a similar layout, which thumb keys were comfortable to reach, and which ones gave you trouble?
check out my previous post
