Circuit boards are often spec’d with a two-dimensional footprint. This works in many situations, but we of course live in a three dimensional world (or more). Kn/vD was annoyed to see a variety of systems claiming to be credit card computers, while entirely neglecting the Z Axis. It’s easy to gripe, but he actually did something about it, creating what he claims to be the world’s thinnest DIY computer. At just 2mm thick, it's wider than most credit credit cards, but much closer than usual.
To accomplish this feat of flatness, Kn/vD is using a PCB in quite a clever manner, as the substrate, body, and input method of the device. The PCB features an array of capacitive touch inputs as a keyboard, avoiding any protruding buttons or switches. Power is provided by an LIR2015 or CR2025 coin cell battery, computing is via a PIC18F47Q83-I/PT chip, and the display is an EA DOGM204-N 20x4 LCD. Rather than positioning these components on top of the circuit board, they are in fact recessed inside the board itself, via holes designed to accommodate each one.
It’s an ingeniously creative PCB use, and Kn/vD notes that it’s a native 8-bit system, unlike other devices that use 32-bit processors to emulate 8-bit computers. Firmware-wise, he even wrote a “Bitling BASIC” interpreter for use here, which is very efficient and can run on this type of minimalistic system.
It’s a spectacular design that could actually fit in your wallet. Perhaps it will inspire others to consider how they can creatively shrink their board’s third dimension!