Designing the Ultimate Programmer’s Split Keyboard

Ergonomics are essential for those of us that spend our days sitting front of computers. When computer keyboards and mice first came along, ergonomics weren’t a high priority. As a result, a lot of people spend decades living with serious pain — physical pain that physically hurts, painfully. The solutions are good posture, a decent chair, proper monitor placement, a trackball mouse, and a keyboard that actually suits human anatomy. Christian Selig is a programmer that desperately needed a better keyboard, but couldn’t find one that he liked. So, he built his own dream keyboard from scratch.

Selig defined a number of criteria for this project. He wanted a split keyboard with a column-staggered ortholinear layout that sorta kinda matches his MacBook, mechanical key switches, wireless connectivity, enough keys to mostly avoid layering, and style. Nothing on the market exactly matched his needs, so he had to make it himself and the result is the Caldera keyboard.

The first step was to select a controller. In fact, Selig needed two of them, because this is a split keyboard with the two halves completely untethered. We live in a DIY keyboard golden age and there are a lot of controllers to choose from, which is great. Selig chose the nice!nano, which retains the popular SparkFun Pro Micro footprint, but with a Nordic nRF52840 microcontroller that has built-in Wi-Fi and Bluetooth connectivity. The nice!nano is also very thin, power efficient, and comes with a USB-C port.

Selig then needed to design PCBs to create the connections between the nice!nano controllers and the key switches. He was able to save a massive amount of time by using an awesome tool called Ergogen, which accepts a layout and configuration, then spits out KiCAD files that make the PCB design a snap.

While Selig was waiting for his PCBs to be fabricated and delivered, he modeled the keyboard case in Autodesk Fusion 360 and then 3D-printed those parts on a Bambu Lab printer. The keyboard case leaves room for a relatively large PlayStation controller battery. Selig estimates that the battery should last for about a year between charges. The nice!nano has onboard charging circuitry to make that easy.

When the PCBs arrived, Selig was able to assemble his new keyboard using Cherry MX key switches. ZMK firmware gave him the exact layout he wanted. He was able to avoid layering, with the minor exception of a few characters (brackets and parentheses).

Now Selig can code in style and comfort all day long. And if you like the Caldera design, he uploaded all of the files so you can build your own.