Embedded Business Card

A business card built as a circuit board. An STM32C011F6 drives a 4×4 grid of 16 LEDs through an AW9523B I²C LED driver, and a LIS2DH three-axis accelerometer lets the board react to being picked up and tilted. It runs straight from USB-C through a TLV757 3.3 V regulator, with ESD protection on the exposed lines.
Debug and expansion stay accessible rather than hidden: a Tag-Connect SWD footprint for programming, and the I²C and SPI buses plus both accelerometer interrupts broken out to labelled pads along the edge. It is a 4-layer board (2 oz outer copper, 1 oz inner, 1.66 mm) in black solder mask with yellow silkscreen and an ENIG finish, drawn in KiCad 10 for JLCPCB.
The part I care most about is the process around it. Every design rule traces to a written record of the fab's capability, and a lint script proves that on every run — a rule file that asks for too little produces a clean DRC report, which is the failure mode this is built to catch. DRC, ERC and review findings are baselined so a new one is visible the day it appears, a release check defines what "releasable" actually means, and a CI pipeline validates, versions and publishes from conventional commits.
The sources are not public.