kicad-pinmap

name	kicad-pinmap
description	Pin-to-net mapping auditor -- verifies that every IC pin in the schematic is connected to the correct net, matched against a pin map source of truth (CSV, datasheet table, or Python dict). Critical for BGA/QFN devices where swap errors are invisible to DRC/ERC.

Why This Matters

ERC and DRC cannot catch a swapped pin. A power pin on a signal net passes all automated checks but produces a dead or damaged board. The only defense is comparing the schematic pin-to-net assignment against the datasheet pinout table.

Pin Map Source Format

# scripts/pin_maps.py
DEVICE_PINMAP = {
    "A1":  "GND",
    "A2":  "VDD_1V8",
    "A3":  "SPI_CLK",
    "B1":  "RESET_N",
    "C4":  "__NC__",   # explicitly no-connect
}

Sources (in priority order):

1. Datasheet pin function table
2. Reference design / eval board schematic
3. Manufacturer application note

Audit Workflow

1. Analyze the schematic with the kicad skill and retain the per-component pin/net data as analysis.json.
2. Compare that data with the checked-in pin-map source. If the project contains a documented audit script, run it; do not assume scripts/audit_pinmap.py exists.
3. Investigate every mismatch; it can be an intentional net alias or a defect.
4. Decide connected/no-connect status for every unmapped pin and update the source of truth.
5. Regenerate the schematic and repeat the audit.

Gap Filling

Unmapped pins should get no-connect markers rather than floating unconnected. Floating digital inputs can cause latch-up or undefined behavior.

Coverage Targets

Flag any IC below 80% mapped. No-connect pins count as mapped.

IC ref	Package	Total pins	Mapped	NC	Coverage
(fill in)

Common Pitfalls

SOT-23 transistors: BCE, BEC, EBC, and CBE orderings all exist for NPN BJTs; GDS, GSD, SGD for N-MOSFETs. The KiCad symbol lib_id suffix encodes an assumed pinout. Verify against the actual MPN's datasheet -- especially when no MPN is set.

Multi-unit ICs: Op-amp and gate packages with a shared VCC/GND unit. Ensure the power unit is placed and connected -- a missing power unit causes an ERC warning that can be overlooked.

Active-low signals: Verify RESET_N, CS_N, OE_N are driven with the correct polarity. A high-true signal on an active-low input means always-asserted.