Sd led card

Hardware Notes

First PCB Revision

Build a full-size SD-card-shaped board that is electrically conservative:

• 3.3 V signaling only.
• SD default speed first.
• No UHS-II contacts.
• ENIG edge contacts.
• Low-current LEDs.
• Test pads for SWD/programming.

Current generated PCB status:

• KiCad DRC: clean, 0 violations / 0 unconnected items.
• KiCad ERC: 0 errors. Remaining warnings are library-table/config warnings from generated embedded SDLED symbols and an intentionally isolated BOOTSEL debug pad.
• The schematic now captures the intended electrical blocks: SD edge contacts, RP2350A, chained addressable side LEDs, capacitive touch, decoupling, and SWD/debug pads.
• The current PCB includes a debug-only breakaway probe tail. It extends past the exposed end of the SD card and brings the nine SD edge contacts out to larger probe pads so host/card behavior can be observed while inserted.
• Components are placed on the same face as the SD contact pads.
• Decorative no-net routing has been removed.
• The remaining production gates are exact LED part/footprint selection, final routed copper, exact manufacturer stackup, and confirmed component heights for the target MacBook SD slot.

Mechanical Z Budget

This design is based on KiCad's SD_Card_Device_16mm_SlotDepth footprint. That template models the inserted contact/mechanical region of a full-size SD card. For the component stack to fit under normal full-size SD thickness, this design targets a 0.8 mm PCB rather than the template's original 1.4 mm note.

The current placement keeps component bodies outside that inserted 16 mm region:

The 0.8 mm stack makes the current known package heights fit below the normal 2.1 mm SD-card thickness. This revision intentionally does not use a local stiffener or thickness buildup, because that complicates fabrication. The main remaining mechanical risk is contact reliability: a 0.8 mm rigid PCB may be too thin for some SD-slot spring contacts even if it physically inserts cleanly.

The next practical step is a cheap bare-board/mechanical coupon with ENIG edge pads. Test insertion, removal, pad contact, and whether the side LEDs remain visible in the target Mac slot before committing to an assembled run.

For bring-up, order the debug-tail Gerbers first. The tail is not part of the final card; cut or flex off the narrow neck after probing, then lightly smooth the exposed edge. Do not use the debug-tail board as the final mechanical fit answer until the snapped edge has been cleaned up and rechecked in the slot.

Run tools/check_mechanical_envelope.py after regenerating the board. It fails if any known package body is placed inside the inserted 16 mm SD-slot region or if any known board-plus-package stack exceeds normal SD card thickness.

Candidate Pin Map

This follows the upstream RP2350 SD emulator default:

Mechanical Notes

Use KiCad's SD-card-device footprint as the starting point for outline and edge pads. The exposed end should contain the LED diffuser windows and any touch electrode. Keep all components out of the deep-insertion region unless a real slot-clearance check proves there is room.

The current capacitive touch electrode is CT1, a bare copper/ENIG pad on the SD-contact side near the exposed lip. It should route to GP7 through the touch-sensing front end. Keep a local ground guard optional for a later rev: the first board should prioritize a large accessible touch area and tune thresholds in firmware.

BOM Direction

• MCU: RP2350A/RP2350B, final package TBD by routing and thickness.
• LEDs: right-angle / side-view RGB LEDs facing the exposed SD-card lip. A top-emitting addressable LED is a poor fit here unless we add a real light pipe, because the laptop slot hides most of the top face.
• Decoupling: local 100 nF caps at MCU and LEDs, plus small bulk capacitance.
• Optional ESD: low-capacitance ESD array on exposed SD lines.