L-ink Card: A Smart Card That Displays What It Does

This is a DIY project for building a tiny smart card that combines NFC (the wireless tech used for contactless payments and access control) with an electronic ink display—the kind of low-power screen you see on e-readers. The card lets you carry multiple card identities in one physical object and see what's stored on it through a small screen on the front.

The creator built this to solve real frustrations with carrying multiple ID cards and access cards. Instead of swapping between different cards, you flip a physical dial on the device to switch between stored card identities, and the e-ink screen updates to show which one is active. You pair it with a companion Android app that lets you customize what information displays on the screen and manage which cards are stored inside.

Under the hood, the project uses a microcontroller (STM32L051) paired with an NFC chip (ST25DV) that handles wireless communication with your phone or card reader. The clever part is that because standard ID cards use a different wireless protocol than what the NFC chip supports, the creator embedded multiple cheap card chips inside and uses the dial to physically switch between them—so you're not trying to emulate different card types in software, just selecting which physical chip is active. The e-ink screen is small (200x200 pixels, black and white), but draws very little power, so the card can stay functional for a long time.

This appeals to makers and tinkerers who want to consolidate their wallet, engineers interested in NFC and embedded systems, or anyone frustrated by the limitations of standard cards. The project includes complete hardware files (circuit diagrams and PCB layouts ready to send to a manufacturer), firmware code for the microcontroller, 3D models for printing a case, and the Android app source. The creator notes that future versions may upgrade to a color e-ink display and a better chipset to handle card emulation in software rather than hardware switching.