Insert Coin Business Card

Insert Coin

A series of interactive business cards that come to life when you insert a CR2032 coin cell. Inspired by the Target gift cards of the early 2000s.

The "Insert Coin" cards are PCB-as-business-card builds where the coin cell is the user interaction: slide it into the holder and the card boots, blinks, listens, taps NFC, then sleeps. Different variants explore different form factors, sensor sets, and animations under the same playful idea.

Variants

Repo layout

insert-coin/
├── docs/                       # cross-variant notes, photos, renders
├── shared/                     # things reused across variants
│   ├── kicad/                  # symbols, footprints, 3D models
│   ├── firmware/               # shared HAL/drivers (LED matrix, NFC, mic)
│   └── tools/                  # build-hex.sh, gerber gen helpers
└── variants/<slug>/
    ├── hardware/               # KiCad project + fab outputs
    ├── firmware/               # PlatformIO project (bringup + production envs)
    └── enclosure/              # 3D-printed sleeves / holders (CAD)

Adding a new variant

Use the slug pattern <form-factor>-v<n>:

• business-card-v2 — next rev of the business-card form factor
• keychain-v1, coaster-v1, badge-v1 — new form factors

Copy the structure of variants/business-card-v1/ (without the KiCad files) as a starting point.

Firmware toolchain

PlatformIO + megaTinyCore targeting the ATtiny1616 over UPDI. Default programmer: SerialUPDI through an FTDI USB-serial adapter (one 4.7 kΩ resistor between TX and RX). Per-variant firmware/README.md has the wiring diagram and build commands.

No PlatformIO on the machine? docs/flasher/ is a browser page at ducky.davidyang.work/flash that flashes a card through an Adafruit UPDI Friend. David builds the .hex with shared/tools/build-hex.sh and sends it; the page does the rest.