NFC Business Card [V3]

The Idea

Paper business cards get lost, thrown away, or forgotten in a jacket pocket within a week. I wanted something people would actually remember, and maybe even show to a friend. So I designed a fully functional PCB business card that lights up, responds to touch, and shares my contact details over NFC with a single tap. This is the third revision of the design.

This project pulled together embedded firmware, PCB design, and a bit of product thinking, since a business card only works if people are willing to keep it.

What It Does

At its core, Endeavour is a smart card built on a PCB substrate instead of paper. Tap it against a phone and it triggers an NFC action, opening a link, saving a contact, or pointing to a portfolio site. On top of that, the card has an onboard LED matrix that can display animations, patterns, or simple text, controlled through two buttons labeled UP and DOWN for cycling through modes.

The name and contact details are silkscreened directly onto the board, so the card looks like a finished product rather than a prototype, while the underlying copper traces are left visible as part of the design rather than hidden away.

Hardware Design

The board is built around a microcontroller that handles both the LED matrix animations and the NFC interaction logic. A dedicated NFC antenna is routed into the PCB itself, tuned to work reliably even though the card is thin and compact. BOOT and RST buttons are included for development and reflashing, sitting near the edge so they are accessible without taking the card apart.

The LED matrix is made up of small surface mount LEDs arranged in a grid, driven through a set of shift registers rather than wiring each LED directly to the microcontroller. This kept the pin count manageable, since the whole matrix can be controlled through just a few data, clock, and latch lines, and it made the routing much cleaner across the board.

Power comes from a 3.7V single cell LiPo battery, chosen to fit within the thickness of a standard card without adding bulk. A dedicated charging circuit is built in as well, fed through a USB-C connector, so the card can be topped up the same way as most modern devices rather than needing a separate charger or coin cell replacements.

Every component was chosen with two constraints in mind: it had to be thin enough to fit in a wallet, and it had to survive being carried around daily without failing.

Firmware

The firmware runs on the microcontroller and handles a few jobs at once. It manages the LED matrix refresh so the animations look smooth rather than flickery, it reads button input for switching display modes, and it manages the NFC controller so a tap reliably triggers the right action on the receiving phone.

I kept the animation system modular, so adding a new pattern to the matrix is a matter of writing a new frame sequence rather than touching the core logic. That made it much easier to experiment with different looks for the card without breaking the NFC handling.

Challenges Along the Way

Fitting an antenna, a microcontroller, driver ICs, and dozens of LEDs onto something the size of a credit card meant routing was tight from the start. Keeping the NFC antenna clear of interference from the LED matrix traces took a few layout revisions, since the antenna needed enough open space around it to read reliably.

Power draw was another consideration. With that many LEDs on board, running the full matrix at once would have drained the LiPo far too quickly, so the firmware only lights a portion of the grid at a time using multiplexing through the shift registers, which kept both the brightness and the battery life in a reasonable range.

Result

Being shipped

What's Next

I would like to explore adding a low power display mode that reacts to how the card is held, along with a companion app so the NFC payload and LED animations can be customized without reflashing the firmware. There is also room to shrink the component count further, which would make the card even thinner and cheaper to produce in small batches for anyone who wants their own version.