# 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).

## ▶ RESUME HERE (session handoff, 2026-07-01)

**State:** branch `port/strip-phase`. Sheets in `carrier/`: root `CM5IO`, `CM5_GPIO`,
`CM5_HighSpeed` (reference, stripped), `M2_Ekey` (E-key, done), `Power` (**stages 1–4 done —
power sheet complete**). Baseline anchor: `analysis/baseline/carrier_stripped.json`.

**Done:** strip phase (microSD/HDMI/MIPI/PCIe-M2); M.2 E-key sheet (PCIe ×1 to CM5); Power
stage 1 (LM74700 ideal-diode input protection → `VIN_PROT`); Power stage 2 (LM61460-Q1
15→`+5v` 5 A, SPICE 5.02 V); Power stage 3 (LM61460-Q1 15→`+3V3_RF` 4 A, SPICE 3.32 V; EN ←
CM5 `PCIE_PWR_EN`/106 + 100k pull-down); Power stage 4 (TPS54202 15→`+3V3_AUX` ~1 A, SPICE
3.315 V; UVLO divider start 10.1 V / stop 8.6 V). Current whole-design **ERC = 133** (all
pre-existing types; a good edit adds **zero new**).

**NEXT ACTION → GPS + PPS distribution sheet** (last new block, see step 5 below): GPS
connector (PPS + UART + 3V3 + GND, powered from `+3V3_AUX`); PPS → TVS → Schmitt buffer
(LVC1G17 @ 3.3 V) → fan-out: CM5 `Ethernet_SYNC_OUT` (J2 pin-6 net, no translator) + 2 header
taps. Reuse the build_*.py generator pattern (new `tools/build_gps.py` or extend build_power).
UART: decide which CM5 UART pins to use (check `CM5_GPIO` — reserve/label; datasheet is the
authority). After that: whole-power-tree budget review, then hygiene pass (title blocks, refdes
numbering — note generated refs like `J_E`/`J_PWR` trip kicad-cli's "annotation errors" warning).

**How to build/verify (every change):**
- Sheets are generated wholesale — edit `tools/build_ekey.py` / `tools/build_power.py`, then
  `python3 tools/build_power.py --apply`. Custom IC symbols go in `carrier/CM5IO.kicad_sym`
  (bare name) AND embed in the sheet as `CM5IO:<name>` — else ERC `lib_symbol_issues`.
- Verify loop (judge by the **integrated root** run, not standalone sub-sheets):
  `kicad-cli sch erc --format json -o /tmp/e.json carrier/CM5IO.kicad_sch` (track delta vs 133,
  zero new types) → `analyze_schematic.py carrier/CM5IO.kicad_sch` + `diff_analysis.py
  analysis/baseline/carrier_stripped.json …` (zero regressions) → for bucks, `simulate_subcircuits.py`.
- Gotchas (full list in memory `port-progress`): grid-snap all coords to 1.27 mm or labels don't
  bind; PWR_FLAG/GND must sit on a real pin coord; pre-existing `+5v` is hierarchical (not global);
  type feedback pins `passive`; connector/module pin types may need remodeling for cross-part ERC.

## 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 + PCIe-M2), ERC 182 → 133, 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 |
| **PCIe-M2 (M-key/NVMe)** | CM5_HighSpeed, CM5IO(root), `.kicad_pro` | (1) HighSpeed `--nets 'PCIE_*' --nc-pins 102,104,106,109,110,112,116,118,122,124` (2) root `--drop-sheet PCIe-M2.kicad_sch` (3) root `--sheet-ports PCIE_CLK_P,PCIE_CLK_N,PCIE_TX_P,PCIE_TX_N,PCIE_nRST,PCIE_RX_P,PCIE_RX_N,PCIE_nCLKREQ,PCIE_PWR_EN,PCIE_nWAKE` (strip dangling HighSpeed sheet-symbol pins) (4) `git rm carrier/PCIe-M2.kicad_sch` (5) manual: remove PCIe-M2 entry from `.kicad_pro` `sheets` array + its ERC exclusion. **Design confirmed: 1× M.2 E-key (Wi-Fi) only, 0× M-key SSD** — the single CM5 PCIe ×1 lane is reserved for the E-key; the freed `PCIE_*` lanes (now NC on Module1 unit 2) will be rewired to the fresh E-key sheet in the add phase. |

**`retire_block.py` gained `--drop-sheet FILE`**: removes the whole `(sheet …)` block by Sheetfile + its `sheet_instances` path (run on the parent sheet). `.kicad_pro` `sheets`-array + ERC-exclusion cleanup is still manual (next tool gap).

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~~ **DONE** (see strip table). Confirmed E-key-only (no M-key SSD).
2. ~~Re-baseline~~ **DONE** — `analysis/baseline/carrier_stripped.json` is the add-phase diff anchor.
3. **M.2 E-key sheet** ✅ **DONE** (`carrier/M2_Ekey.kicad_sch`, generated by `tools/build_ekey.py`).
   J_E = KiCad `Connector:Bus_M.2_Socket_E`, fp `Connector_PCBEdge:M.2_2230-xx-E`. PCIe link-0 wired to the
   9 freed CM5 pins via **global labels** (PCIE_TX/RX/CLK ±, nRST, nCLKREQ, nWAKE — netlist-confirmed J_E↔Module1);
   `+3V3_RF` (4 pins) + 10µF∥2×0.1µF decoupling + temp PWR_FLAG; 11 GND; W_DISABLE1/2 10k pull-ups to +3V3_RF;
   ~41 NC (USB/BT, PCM/I2S, SDIO, UART, COEX, I2C, link-1). RX **not** coupled on carrier (card-side per M.2; BOM C_PCIE removed).
   **Verify:** ERC 133→133 (zero new); analyzer diff +7 added, **0 regressions**.
   Connector-symbol pin types remodeled for cross-connector ERC: lines CM5 drives → `passive`; lines the card
   drives into CM5 inputs (RX pair + CLKREQ#/WAKE#) → `output`.
   **Open items (review/next):** (a) CM5 `PCIE_PWR_EN` (pin 106) still NC — wire to the +3V3_RF buck EN in the
   power sheet; (b) the temp PWR_FLAG on +3V3_RF must be REMOVED once the buck drives it (else dual-driver ERC);
   (c) optionally route `WIFI_DISABLE#` to a CM5 GPIO for SW radio control; (d) analyzer CG-AUD 5:1 sig/gnd on J_E
   is inherent to the M.2 connector (INFO, not fixable). New tool: `tools/build_ekey.py` (place connector + auto-NC + labels).
4. **Power sheet** (`carrier/Power.kicad_sch`, generated by `tools/build_power.py`) — staged, **sync + datasheet-built parts** (user choice). **Spec rating fix:** the spec's buck candidates miss its own ≥20V-Vin rule (TPS54424=17V, TPS54560=async) — selecting synchronous ≥30V parts instead (LM61460-class 6A for +5V & +3V3_RF/4A; TPS54202 28V for +3V3_AUX), each verified vs datasheet before commit.
   - **Stage 1 — input protection ✅ DONE.** J_PWR(15V) → D_REV `LM74700-Q1` ideal-diode + Q_REV N-FET (reverse-polarity/-current) → `VIN_PROT`; `SMBJ18A` TVS + 100µF/25V ∥ 10µF/50V bulk; C_VCAP charge-pump cap. Netlist-verified topology; ERC 133→133 (zero new); analyzer 0 regressions. **Confirm vs LM74700-Q1 datasheet:** C_VCAP value, EN-to-+15V_IN, FET pick (Vds≥30V, SOA/inrush) + optional gate R.
   - **Stage 2 — U_BUCK5 15→`+5v` 5A ✅ DONE.** `LM61460-Q1` (6A, 42V absmax sync; **custom symbol built from the datasheet** → `carrier/CM5IO.kicad_sym` as `CM5IO:LM61460-Q1`, fp `Package_SO:Texas_HTSSOP-14-1EP…ThermalVias`). VREF=1.0V → FB divider R_FBT5 40.2k / R_FBB5 10.0k = **5.02V (SPICE-confirmed vfb=1.0V)**. L5 4.7µH, Cout 2×47µF/16V, Cin 2×10µF/50V, Cboot 100n+Rboot 4.7Ω, RT 31.6k(~400kHz), BIAS→+5v, EN→VIN_PROT, PGOOD 100k→+5v. **`+5v` kept HIERARCHICAL** (pre-existing carrier net; global would collide `same_local_global_label`) — Power sheet exposes a `+5v` sheet pin, tied into the root `+5v` net; netlist-verified it drives Module1 + GPIO + USB. ERC 133→133 (zero new); analyzer +32 added **0 regressions**; SPICE 12/13 pass, 1 benign warn (L5/Cboot mis-detected as LC filter). **Confirm vs datasheet:** RT freq, L sat ≥7A, EP=pad15, optional EN UVLO divider.
   - **Stage 3 — U_BUCK33R 15→`+3V3_RF` 4A ✅ DONE.** Second `LM61460-Q1` (shared BOM with stage 2: L 4.7µH/7A ripple ~1.3A=33%, Cin 2×10µ/50V, Cout 2×47µ/16V, RT 31.6k ~420kHz, Cboot 100n+Rboot 4.7). FB divider R_FBT33 23.2k / R_FBB33 10.0k = **3.32V (SPICE: vfb 0.994V, inrush settles 3.32V)**. BIAS→`+3V3_RF` (datasheet: valid ≥3.1V, auto-falls back to VIN below). **EN ← CM5 `PCIE_PWR_EN`** (Module1 pin 106: NC swapped for a global label on `CM5_HighSpeed`) + **R_EN33 100k pull-down** (mirrors reference R14 — netlist-verified `Module1.106 + U_BUCK33R.7 + R_EN33.1`) so the Wi-Fi rail is OFF until the CM5 asserts it. **E-key temp `#FLG33RF` PWR_FLAG removed** (build_ekey); the buck's PWR_FLAG on L33.2 is now the sole `+3V3_RF` driver — netlist shows buck + all 4 J_E power pins + pull-ups + decoupling on one net. Verify: ERC 133→133 zero new; analyzer +49 added **0 regressions**; SPICE 17 pass / 2 benign warn (the L/C_BOOT "LC filter" mis-detect, once per buck) / 0 fail. (Note: `kicad-cli` netlist export prints a pre-existing "annotation errors" warning — un-numbered generated refdeses like `J_E`/`J_PWR`; present at fd627f5 too, cosmetic.)
   - **Stage 4 — U_BUCK33A 15→`+3V3_AUX` ~1A ✅ DONE (power sheet complete).** `TPS54202` (SOT-23-6, sync, fixed 500kHz, VFB=0.596V). **Abs-max gate PASSED but thin:** VIN abs-max **30V** vs SMBJ18A clamp ≤29.2V at full rated 600W surge → 0.8V transient margin (operating max 28V is not the surge number). Custom symbol `CM5IO:TPS54202` (the KiCad lib symbol `extends TPS54302` — no own pins, can't embed standalone) + bare copy in `carrier/CM5IO.kicad_sym`. FB per TI's 3.3V table row: **100k/22.1k + Cff 56pF → 3.29V (SPICE: vfb 0.597V, inrush settles 3.315V)**. L 10µH/2.5A (ΔI~0.52A), Cout 2×22µF/16V, Cboot 100n, Cin 10µF/50V+100n. **EN abs-max is only 7V → NO direct VIN tie** (unlike LM61460): UVLO divider **866k/110k** (solved from Ip=0.7µA/Ih=1.55µA, VEN 1.21/1.19V) → **start 10.13V / stop 8.61V**, EN ~1.9V at 15V in (~3.5V at 29V clamp — safe). FB+EN pins typed `passive` (divider-only nets). Verify: ERC 133→133 zero new; analyzer +65/−0 zero regressions (warn/error set identical to stage 3); SPICE 23 pass / 2 benign warn / 0 fail / 0 skip. **New tooling gap found:** `simulate_subcircuits.py` lowercases refdeses into SPICE names — `C_IN33A` vs stage-3 `C_IN33a` collided ("device already exists") and silently SKIPPED the whole VIN_PROT decoupling group → renamed to `C_IN33Aa`. Rule: **never create refdeses differing only by case.**
5. **GPS + PPS distribution**: GPS connector (PPS+UART+3V3+GND); PPS → TVS → Schmitt (LVC1G17) →
   fan-out: CM5 `Ethernet_SYNC_OUT` (J2 pin-6 net, 3.3V, no translator) + 2 header taps. SPICE/timing check.

## 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.
