Microcouple
Microcouple is a pair of small RP2040 boards that talk to each other over infrared. Each one carries an LED matrix, capacitive touch pads, USB-C, and LiPo charging. Mostly it was a PCB-design exercise: how much circuitry has to sit around an RP2040 before it's a usable board.
The schematic covers the RP2040, IR transmit circuitry and a 38 kHz receiver, an LED matrix, capacitive touch inputs, USB-C, LiPo charging, and — from revision 2 onward — a W25Q128 QSPI flash device.
That flash was the correction. On revision 1 I saw "SoC", assumed I could just place the RP2040 and go, and left off the external QSPI storage the chip actually boots from. Revision 2 adds the 128 Mbit W25Q128 and routes the QSPI bus properly. "System on chip" doesn't mean "system on board".
The hardware side is fairly complete — KiCad hierarchy, PCB layout, fabrication outputs, 3D model — but there is no firmware. firmware/src/main.py is empty. The IR protocol, touch pads, LED animations, and USB behavior were never written.
Schematic (page 1):
