PolyKybd Gives Every Key Its Own OLED Display

We're actually pretty lucky that keyboard key caps are somewhat standardized and interchangeable, as that kind of modularity is rarely present in other devices. But those key caps are still printed with static legends, which means you have to either swap them out if you're changing the function or deal with keys crowded with extra markings for alternate layers. While that isn't a problem for the average computer user, it can be a serious inconvenience for those who switch between different mappings. To solve that problem, thpoll designed the PolyKybd mechanical keyboard with an OLED display on every key.

The benefit here should be obvious: the legend on each key is configurable. So if you switch to an alternate key map or layer, the legends can update to reflect the new characters and functions. This would, for example, be handy for gaming. You could swap over to a game-specific map and the key cap legends would change to match the new functions, like "W" becoming an up arrow or "1" becoming a health potion symbol. The same benefits would apply to more serious tasks, like video editing or CAD (Computer-Aided Drawing) work.

For this to work, every key needs its own screen mounted on top of the key cap. That is a lot of screens (72 just for the keys, to be exact). Each screen is a tiny 0.42" OLED model that receives signals via SPI. A single SPI display typically requires four wires for data and sync, plus two power wires. There aren't any microcontrollers on the market with enough pins to connect all of the screens directly — much less the screens and the key switches. So the PolyKybd uses chained shift registers. That lets the Raspberry Pi RP2040 microcontroller address and update each displayas necessary, and also monitor the matrix of key switches to detect key presses.

PolyKybd has a few extra features, in addition to the key screens. It has a place to attach a rotary encoder, scroll wheel, or mini trackball for switching modes, along with two larger OLED screens to display information about the current state.

The enclosure was designed in OpenSCAD and is 3D-printable. The custom PCB fits inside that and accepts mechanical key switches. The key caps are transparent models that fit over the screens on the keys. This is a split keyboard design with an ergonomic layout, which should ensure comfort while typing. It runs QMK firmware for maximum customizability.

PolyKybd is still a work in progress, with just a few hardware kinksleft to iron out. But the current prototypes look very promising and we have every reason to expect that the PolyKybd project will reach completion.