A Fresh and Functional Keyboard

For keyboard connoisseurs, building a custom keyboard is not only a right of passage, but also something of a necessity. Finicky typists are able to find a problem with any and every keyboard that leaves it lacking. The most common solution to this problem involves purchasing a set of mechanical switches with just the right tactile, clicky, or linear action and the perfect set of keycaps, all arranged in an optimal configuration that is ideally suited to the individual user’s typing habits.

With hundreds of different options out there in the world of mechanical switches, buying off-the-shelf components and assembling a keyboard fits most use cases. But sometimes keyboard aficionados have special requirements that nothing on the market can exactly meet. That was the case for YouTuber flurples, who wanted a very compact wireless keyboard that can be carried around in an Altoids tin — called the Mintboard.

Needless to say, traditional mechanical keyboard switches and keycaps are not an option. After all, the tin only measures 96 x 56 x 21 millimeters. Due to the diminutive size of this case, flurples decided to go with a 40% keyboard, despite the fact that a 60% configuration was actually desired for the project. Even the 40% configuration would only give about seven millimeters of spacing between key centers. Ultimately, push button switches — 6.5 millimeters in length counting the contacts — were chosen for use. This would allow a more comfortable key spacing of 7.3 millimeters for the 12-key wide grid of a 40% keyboard.

A PCB was designed in KiCad, with the switches occupying one side, and space for the Arduino Pro Micro-compatible nice!nano v2.0 development board on the other side. The nice!nano was chosen because it offers Bluetooth support thanks to an nRF52840 SoC, which is needed to make the keyboard wireless. An on/off switch and battery connector were also included in the design, then the edges of the board were rounded to fit in the Altoids tin.

A 3D-printed base, key cutouts, and keycaps were designed and produced to round out the hardware design. These initially did not quite fit. The key cutouts were too tight, leaving the keys permanently depressed. No big deal — 3D printers allow for rapid iteration, so a new version was quickly produced. This was a better fit, but still not quite right. But now flurples was out of filament, which was a problem. So, as a temporary fix, layers of blue tape were added between the PCB and key cutout to get the spacing just right.

Next, holes were cut in the Altoids tin for access to the on/off switch and USB port. Then the internal components were mounted in the case with double-sided tape. That only left the firmware to be completed. Previously, flurples had used QMK, but unfortunately, that does not support Bluetooth. So, alternatively, ZMK firmware was utilized. After defining the keyboard layout and pin mappings to the microcontroller, ZMK was found to work quite well.

At that point, the keyboard was fully functional — but it is hard to call a keyboard complete without labels on the keycaps. Using Adobe Illustrator, a set of labels were designed. These were then cut out of a material using a Cricut machine. They were then placed on the keys and topped off with a UV-curing nail topcoat. This protected the labels and also added a raised texture to the keys.

The Mintboard looks great and certainly meets the requirements of fitting in an Altoids tin and being wireless. Of course this device is not right for all situations. At its core, the keyboard is still composed of a bunch of cheap push buttons that are challenging to type on with actual human-sized hands. But in a pinch, it looks like a good option for mobile use.