step5-routing

Step 5 · Routing

Session & state check (before touching anything)

1. One step per session: if this session already did substantive work for another step, stop and ask for a fresh session.
2. Read docs/flow-state.md (canonical header line; foreign file → stop and ask). Confirm step 4 is done; read the placement deliverables, the critical-signal definitions in docs/dev-plan.md, and the BOM. Not satisfied → stop and report.
3. This step already done with no issue targeting it → re-run: ask intent first. Already in-progress → aborted or concurrent session: ask before proceeding. Marked rework (usually cascaded from a placement/schematic fix) → redo what the rework note requires, then wrap up. Marked parked (the user accepted an unconverged draft) → this re-entry IS the un-park: confirm the user means to resume, then continue the convergence loop from the copper as it stands; when it converges, close the deferred issue that carries the gap, citing the run that closed it — nothing else ever retires that entry, and step 7's definition-of-done would otherwise re-present a gap that no longer exists.
4. Orphan-fix scan: check docs/rework-log-*.md for self-help attempts journaled but never marked adopted/rejected — a previous session died mid-change. Reconcile against the live EDA first (the journal lists touched objects and prior values): roll back or complete the check, then proceed.
5. Issues-table entries with target step = 5 → fix mode.
6. Set step 5 in-progress. Rebuild context from disk only.

Execute

Adopt-and-audit path: inherited routing recorded in flow-state (inherited: <path>, same-EDA only) is ingested, then audited by this step's own bar — DRC plus all three closing checks below. The bar doesn't move; only the labor does.

Routing disciplines

• Engineering order: reference planes / return paths and net classes established first, then wide power traces → critical signals (switch nodes / differential pairs / sense lines) → buses → the rest → GND stitching and pours last (pouring last is tool sequencing — return paths were designed first, not last)
• A missing high-level convenience API (autoroute, pour) ≠ the capability doesn't exist: drop to primitive APIs (draw track / place via) and build the routing net by net; exhaust the low-level interface before giving up
• The EDA's own autorouter is off-limits to the AI. Autorouted copper bypasses the engineering order and lands un-audited; driving a GUI autorouter by blind clicking is a proven tar pit (hours of zero output in practice). Being stuck is never a reason to reach for it — the sanctioned outlets for stuck are self-help and then the wall procedure, in that order. Copper the USER chooses to produce in the GUI, by whatever means, is their call — it re-enters through DRC + the closing checks + verification like everything else.
• API/bridge discipline (e.g. EasyEDA's websocket bridge — any asynchronous execution channel): after a timeout the EDA-side script may still be running — poll for completion, never re-send; batch scripts must be idempotent (an interrupted run leaves half-finished state)
• Impedance control: compute electrical length vs. rise time first (lumped/distributed boundary ≈ t_r·v/6 — a screening estimate, not sign-off); short lumped-region links need matched length at most, and only where a skew budget actually exists
• Critical loops (switch nodes, high dV/dt): shortest path, fewest vias