# PT2 Fake CCU

This folder contains a small modular fake-CCU runner for the Sony RCP PT2-style serial link.

The first goal is simple:

1. Open the RCP serial link at `38400 8E1`.
2. Optionally wait for heartbeat.
3. Seed active selector-zero state.
4. Listen for complete RCP report frames.
5. Immediately answer report-looking frames with the neutral command-5 ACK:

```text
05 00 40 00 00 1F
```

ROM and emulator evidence says this consumes the outstanding report cursor without triggering COPY or lamp/display side effects.

## Run

Dry-run configuration:

```powershell
.\.venv\Scripts\python.exe scripts\ccu_emulator.py --dry-run
```

Run against the bench RCP on COM5:

```powershell
.\.venv\Scripts\python.exe scripts\ccu_emulator.py --port COM5 --duration 30 --log captures\ccu-keepalive.txt
```

Power-cycle first through the COM6 relay:

```powershell
.\.venv\Scripts\python.exe scripts\ccu_emulator.py --port COM5 --power-cycle --relay-port COM6 --duration 30 --log captures\ccu-keepalive-powercycle.txt
```

Try the older three-frame CONNECT cadence seed instead of the command-0 active seed:

```powershell
.\.venv\Scripts\python.exe scripts\ccu_emulator.py --seed connect-sequence --seed-gap 0.700 --duration 30
```

Optionally add periodic state refresh traffic:

```powershell
.\.venv\Scripts\python.exe scripts\ccu_emulator.py --refresh-active --refresh-interval 0.600 --duration 30
```

## Layout

- `frames.py`: checksums, built-in frames, and simple host-frame builders.
- `policy.py`: decides whether an RCP frame should be ACKed.
- `refresh.py`: optional periodic state-refresh scheduling.
- `serial_link.py`: serial read/write plus checksum-resync frame detection.
- `controller.py`: event loop and stats.
- `cli.py`: command-line entry point.

## Why Periodic Lamp/Value Writes Help

Repeated button/lamp/status writes probably do play into the normal CCU flow. The ROM reloads the broad `F9C5` session watchdog on every complete six-byte RX frame, and command-0/command-4/command-6 table writes refresh the selector tables that drive lamps, readouts, and menus.

So a real CCU likely does both:

- reactively ACK RCP reports so the report queue advances, and
- stream or refresh panel state so the visible UI remains current.

The first version keeps those concerns separate: reactive ACKs are always available, while periodic refresh frames are opt-in with `--refresh-frame` or `--refresh-active`.
