# 4-layer wide-power autoroute — run on your Mac, then hand me the .ses

**The board is now 4-layer.** Stackup: **F.Cu / In1.Cu (GND plane) / In2.Cu / B.Cu** (JLC
standard 1.6 mm). GND is a solid inner plane, so wide power stops fighting for space — this is
the fix for the 2-layer congestion (51 unrouted at 1.0/0.8 mm).

**File:** `hbox-watchdog-v3-PROD-4layer-wideclass.dsn` — current placement, **unrouted**, with:

| Class | Width | Nets |
|---|---|---|
| **PWR_HI** | **1.5 mm** | BAT_PLUS, SW_BAT, MAIN5V, VEH5V, SYS5V, VIN_SW |
| **PWR_MID** | **1.0 mm** | SW_5V, 3V3_MODEM, 5V_FAN, 24V, 24V_IN, IGN_IN, SW_FAN, SW3_NODE, FAN_RET |
| kicad_default | 0.2 mm | signals |
| GND | — | **In1.Cu plane** (routed as a plane, not traces) |

Routing layers = F.Cu + In2.Cu + B.Cu (+ In1 gaps), GND on the In1 plane. Plenty of room for
1.5 mm power now.

## 1. Route it
```bash
cd "~/Documents/Claude/Projects/Drogheda/03-Architecture-Hardware/kicad"
java -jar freerouting-1.9.0.jar
```
File → **Open Design** → `hbox-watchdog-v3-PROD-4layer-wideclass.dsn`. Let it route; watch the
**incomplete** count — on 4 layers it should drive to **0** (or single digits), not stall.
Then File → **Export Specctra Session File** → `hbox-watchdog-v3-PROD-4layer-wideclass.ses`.

Headless alternative:
```bash
java -jar freerouting-1.9.0.jar -de hbox-watchdog-v3-PROD-4layer-wideclass.dsn \
  -do hbox-watchdog-v3-PROD-4layer-wideclass.ses -mp 100
```

## 2. Bring it back
Tell me the `.ses` is ready and I'll import it → refill the In1 GND plane → DRC → render, same
as before. (Backups: `…bak-pre4Lroute-*`, `…bak-preAutoroute-*`, `…bak-postAutoroute-*`.)

## 3. When you order at JLCPCB
Select **4 layers** (JLC 4-layer 1.6 mm, ~a few $ more than 2-layer). The stackup in the board
is the standard one JLC applies automatically. Worth it here: solid GND for the three switchers
+ the 4G modem, and it's why the power routes.

## Notes
- Widths are conservative-but-real (≥ guide spec, comfortably routable on 4 layers). Want the
  original 2.5 mm on PWR_HI? Edit `(width 1500)` → `(width 2500)` in the `.dsn` — there's room now.
- Still a fresh full route, so expect a few sensor/GND opens to close interactively after import.