# GoodWe RS485 Controller — Home Assistant add-on repository

Replaces a GoodWe battery inverter's vendor controller with a local one: holds
net grid exchange at zero by emulating the inverter's smart meter over RS485,
and runs the monthly battery maintenance cycle the vendor box was doing.

```
repository.yaml            add-on repository metadata
goodwe_controller/         the add-on
  config.yaml              manifest + options schema (the per-site config form)
  app/                     the controller
    control.py             the control law — pure functions, no I/O
    maintenance.py         the monthly cycle state machine
    hass.py                Supervisor/Core API access
    store.py               persistent state in /data
    mqtt.py                optional status entities
    web.py                 ingress UI
    main.py                orchestration, heartbeat, failsafe behaviour
  test_control.py          runnable checks — no framework needed
  test_maintenance.py      runnable checks — walks a full cycle in fake time
  DOCS.md                  the add-on's documentation tab
firmware/goodwe-master.yaml  ESPHome config for the T-CAN485
estop/rs485_log.py           optional RS485 e-stop / bus witness
docs/GoodWe-RS485-Field-Guide.pdf  the guide techs carry (10pp, A4)
docs/build_guide.py          its single source - rebuilds the HTML and PDF
FIELD-GUIDE.md             how to edit and rebuild the guide
```

## Install

Settings → Add-ons → Add-on store → ⋮ → **Repositories** → add this repository's
URL, then install **GoodWe RS485 Controller**.

Requires **Home Assistant OS or Supervised**. Add-ons cannot be installed on HA
Container or Core.

## Read this first

**The inverter holds its last command forever.** It has no meter-timeout of its
own — a controller that dies mid-command leaves the battery running until a
human intervenes. Measured on real hardware: 5 kW of discharge held for 113
seconds after a controller went silent.

Three layers exist because of that, and only the third covers the Home Assistant
machine itself dying:

1. **ESP32 watchdog** — no fresh setpoint for ~30 s → command 0 W, and keep
   commanding it.
2. **Wind-down before firmware updates** — 0 W written before the update starts.
3. **RS485 e-stop (optional)** — writes 0 W after 30 s of total bus silence.

Sites sold without the e-stop must have the acknowledgement in `FIELD-GUIDE.md`
§10 signed.

## Development

The control law and the maintenance machine are pure Python with no Home
Assistant imports, so they run anywhere:

```bash
cd goodwe_controller
python3 test_control.py
python3 test_maintenance.py
```

Both must pass before shipping any change. They are not unit-test theatre —
each assertion corresponds to a rule whose absence produced an observed failure
on real hardware, and the comments in `control.py` say which.

## Compatibility

- GoodWe **ES / BP family** inverters (AA55 / RS485 meter-bus generation)
- The protocol is **reverse-engineered**. There is no vendor contract, and a
  firmware change on GoodWe's side could break every installation at once. Say
  so when you sell it.