# TwinCAT driver — v3 backlog

The v2 TwinCAT driver is considered solid: 28 integration tests (14 `[TwinCATFact]` +
16-case `[TwinCATTheory]`) running live against the TCBSD fixture, 110 unit tests,
three latent driver bugs shaken out (notification cycle units, `STRING(N)` mapper,
bit-indexed BOOL path). Further work is deferred.

Archived from `docs/drivers/TwinCAT-Test-Fixture.md` § Follow-up candidates.

## Deferred items

1. **TC2 coverage** — spin up a TC2 runtime (Windows CE IPC or legacy XAR)
   and run the same suite; any delta surfaces. Blocked on hardware.

2. **Notification coalescing under load** — run the subscribe test while
   the PLC cycle is saturated (bump `lineSim` complexity, watch for
   dropped notifications). Doable on current rig; deferred as lower
   priority than v3 feature work.

3. **Multi-hop AMS route** — add a test behind an IPC gateway with a
   chained route entry. Blocked on hardware (gateway IPC).

4. **License-rotation automation** — XAR's 7-day trial expires on
   schedule. Either automate `TcActivate.exe /reactivate` via a scheduled
   task on the VM (not officially supported; reportedly works for some
   TC3 builds), or buy a paid runtime license (~$1k one-time per runtime
   per CPU) to kill the rotation. Ops item, not code.

5. **Lab rig** — cheapest IPC (CX7000 / CX9020) on a dedicated network;
   the only route that covers TC2 + real EtherCAT I/O timing + cycle
   jitter under CPU load. Blocked on hardware + budget.
