# CM5 Carrier Port — Status & Handoff

> Handoff doc for whoever (human or LLM) continues this work. Read this first, then
> `.claude/skills/kicad-port/SKILL.md` (the mandatory workflow/verify-loop), then
> `CM5_Carrier_Design.md` (frozen rev-A spec).

## What this repo is

Two intertwined goals:
1. **Improve Claude's EDA tooling** — the [`kicad-happy`](https://github.com/aklofas/kicad-happy)
   skill suite (`kicad`, `datasheets`, `spice`, …), wired in as Claude Code skills via
   `~/.claude/skills/{kicad,datasheets,spice} -> kicad-happy/skills/*` symlinks. The toolkit
   clones (`kicad-happy/`, `kicad-claude-toolkit/`, `MCP-KiCad/`) are gitignored — re-clone if missing.
2. **Port the Raspberry Pi CM5IO reference into a custom CM5 carrier board** — the real
   test bed (PTP/timing instrumentation node: 15V→5V front end, GbE magjack, M.2 E-key Wi-Fi
   (AW7915/MT7915), 2×USB-A, USB-C programming, RTC, GPS-PPS distribution).

Method is **diff-from-reference**: `refs/` holds the untouched CM5IO reference; `carrier/` is the
working copy. Every edit is verified against `analysis/baseline/cm5io.json`.

## Environment / tooling state (macOS, Homebrew)

- `kicad-cli` ✅ (`/opt/homebrew/bin/kicad-cli`) — ERC + netlist export
- `poppler` ✅ (pdftotext) — datasheet page selection
- `ngspice` ✅ — `spice` skill; full verify loop validated on the reference (8 subcircuits pass)
- Python ≥3.10 (Homebrew 3.14)

## The verify loop (run after EVERY schematic edit)

```bash
SCH=carrier/CM5IO.kicad_sch ; KSCR=~/.claude/skills/kicad/scripts
kicad-cli sch erc --exit-code-violations --format json -o /tmp/erc.json "$SCH"   # hard gate
python3 $KSCR/analyze_schematic.py "$SCH" -o /tmp/head.json                       # structural
python3 $KSCR/diff_analysis.py analysis/baseline/cm5io.json /tmp/head.json --text # vs baseline
```
- **Track the ERC DELTA, not the absolute** — the reference already has 182 pre-existing
  violations (mostly `unconnected_wire_endpoint`). A good edit introduces **zero new types**.
- The **analyzer diff is the semantic gate** (names broken design intent); **ERC is the hygiene gate**.
- For kept-block integrity, also diff `kicad-cli sch export netlist` before/after — it caught a
  mis-inventoried part (see R8 below).

## Datasheet extraction (done)

CM5 module extracted to `datasheets/extracted/SC1466_43a9ec.json` (200 pins, score 8.7/10,
queryable via `~/.claude/skills/datasheets/scripts/datasheet_features.py`). Drove the NC pin
lists for every strip (e.g. HDMI Module1 pins = all pins whose datasheet name starts `HDMI`).

## The strip tool: `tools/retire_block.py`

General block-retirement for these s-expr sheets. Capabilities:
- excise symbols by Reference; retire nets by name-glob (all label types: local / hierarchical / global)
- **anchor-aware wire removal** (union-find): removes a wire only if its connected component
  reaches no *kept* anchor (kept non-power pin or kept label) AND is seeded by this edit — so
  shared nets survive and pre-existing dangles are untouched
- place `(no_connect)` on exposed Module1 pins (pin coords via a validated transform
  `abs=(px+rot(lx,ly).x, py-rot(lx,ly).y)`, rot0/no-mirror; refuses other orientations)
- clean orphaned power flags, dangling NCs, orphaned labels
- `--sheet-ports NAME,...` removes root-sheet hierarchical pins + connecting wires

Usage: `python3 tools/retire_block.py <sheet> --symbols J7,U18 --nets 'SD_*' --nc-pins 57,61 [--sheet-ports ...] [--apply]` (dry-run without `--apply`).

**Known gap (next improvement):** does NOT auto-prune orphaned power-label/wire *stubs* left after a
connector is removed (e.g. leftover `+3.3v`/`HDMI_5v` labels). Those were cleaned manually — see git history.

## Strip phase — DONE (microSD + HDMI + MIPI), ERC 182 → 136, 0 new violations, 0 regressions

| Block | Sheet(s) | Command(s) (run with `--apply`) |
|---|---|---|
| **microSD** | CM5_GPIO | `--symbols J7,U18,C5 --nets 'SD_*' --nc-pins 57,61,62,63,67,69,75` |
| **HDMI** | CM5_HighSpeed | `--symbols J22,J10 --nets 'HDMI0_*,HDMI1_*,HDMI_5v' --nc-pins 143,145,146,147,148,149,151,152,153,154,158,160,164,166,170,172,176,178,182,184,188,190,199,200` |
| **MIPI/camera** | CM5_HighSpeed, CM5_GPIO, CM5IO(root) | (1) HighSpeed `--symbols J5,J16 --nets 'DPHY0_*,DPHY1_*,SCL1,SDA1' --nc-pins 115,117,121,123,127,129,133,135,139,141,175,177,181,183,187,189,193,194,195,196` (2) GPIO `--nc-pins 80,82,97,100` (3) root `--sheet-ports SCL0,SDA0,CAM_GPIO0,CAM_GPIO1` (4) HighSpeed `--symbols R8 --nets 'SCL0,SDA0'` (5) manual: remove 3 orphaned +3.3v labels + 2 wire stubs |

Notes that bit us (don't re-learn the hard way):
- **MIPI lanes are labeled `DPHY0_*`/`DPHY1_*`, NOT `MIPI*`.** The connectors J5/J16 are camera FFCs
  bundling DPHY + cross-sheet I2C0 (`SCL0/SDA0`) + `CAM_GPIO0/1` — a 3-sheet hierarchical block.
- **`R8` is a camera pull-up, not USB** (the Explore-agent inventory was wrong). Confirmed via
  `kicad-cli sch export netlist` (`R8.2 → J16.17`). Always verify inventory against the netlist.
- **`SCL0/SDA0` (I2C0) are camera-only 2-node nets** (netlist-proven). NC'd to **reserve I2C0 for a
  future external I2C RTC** (CM5's own RTC is on-module via VBAT). If you add an external RTC, wire it here.

## Next steps

1. **Drop the PCIe-M2 sheet entirely** (NVMe M-key — not used; the M.2 **E-key** Wi-Fi will be a
   FRESH sheet in the add phase, per design decision). Use `--sheet-ports` for its root hierarchical pins.
2. **Re-baseline**: capture a new analyzer baseline of `carrier/` so the add phase diffs against the
   stripped design, not the original reference.
3. **Add phase**: 15V→5V buck front-end (reverse-protection + TVS), M.2 E-key (PCIe Gen2 ×1 +
   CLKREQ/PERST/RF_KILL + 3.3V), GPS connector, PPS distribution (GPS PPS → TVS → Schmitt buffer →
   fan-out: CM5 `Ethernet_SYNC_OUT` + 2 header taps). SPICE-validate the buck divider + PPS network.

## Out-of-repo notes

Richer running notes live in this machine's Claude memory:
`~/.claude/projects/-Users-noise-Documents-obsidian-rpiboard/memory/` (`project-cm5-eda`,
`port-progress`, `eda-tooling-gaps`, `tooling-installs-cm5`). This doc is the portable subset.