Hi-Mit II — Home Assistant Integration

A custom Home Assistant integration for the Hisense Hi-Mit II Air-to-Water heat pump (ATW), reverse-engineered from the official mobile app APK.

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Features

Platform	Entity	Description
binary_sensor	Heat Pump Running	Reports whether the compressor / A2W unit is active
sensor	Circuit 1 Water Temp	Live actual water temperature — Circuit 1 (fixedDid18)
sensor	Circuit 2 Water Temp	Live actual water temperature — Circuit 2 (fixedDid19)
sensor	DHW Water Temp	Live actual domestic hot water temperature (fixedDid16)
sensor	Pool Water Temp	Live actual swimming pool temperature (fixedDid17)
sensor	Outdoor Ambient Temp	External sensor reading (swj_Ta)
sensor	Room 1–8 Temp	Individual room sensor readings (TsR1–TsR8)
switch	Circuit 1 (Heating)	Enable / disable Circuit 1
switch	Circuit 2 (Heating)	Enable / disable Circuit 2
switch	Domestic Hot Water	Enable / disable DHW heating
switch	Swimming Pool	Enable / disable pool heating
number	Circuit 1 Setpoint	Water temperature target for Circuit 1 (°C)
number	Circuit 2 Setpoint	Water temperature target for Circuit 2 (°C)
number	DHW Setpoint	Domestic hot water target temperature (°C)
number	Pool Setpoint	Pool water target temperature (°C)

Setpoint min/max limits are read live from the device (the pump reports its own allowed ranges per heating/cooling mode).

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Installation

HACS (recommended)

1. In HACS → Integrations → ⋮ → Custom repositories
2. Add this repository URL, category Integration
3. Install Hi-Mit II
4. Restart Home Assistant

Manual

# From your HA config directory
git clone https://github.com/YOUR_USERNAME/HiMitII_HomeAssistant.git /tmp/himit
cp -r /tmp/himit/custom_components/himit config/custom_components/himit

Restart Home Assistant.

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Configuration

1. Settings → Integrations → Add Integration
2. Search for Hi-Mit II
3. Enter your Hisense / Hi-Mit II account email and password
4. If your account has multiple homes, select the one with your heat pump
5. Done — entities appear immediately and update every 30 seconds

Token handling

The integration handles authentication automatically:

• The access token is refreshed silently before it expires using the stored refresh token
• If the refresh token also expires, a Re-authenticate prompt appears in the Integrations page — no need to delete and re-add the integration
• All tokens are stored securely in the Home Assistant config entry (.storage/)

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Forcing a Data Refresh

By default the integration polls every 30 seconds. If you need an immediate update there are two options:

1. Built-in service call (no code changes needed)

Call the standard Home Assistant service on any of the integration's entities:

service: homeassistant.update_entity
target:
  entity_id: sensor.hi_mit_ii_circuit_1_water_temp

This triggers coordinator.async_request_refresh() immediately.

2. Dedicated Refresh button entity

A button platform can be added to expose a single Refresh button in the UI / dashboard:

class HimitRefreshButton(HimitEntity, ButtonEntity):
    _attr_name = "Refresh"
    _attr_icon = "mdi:refresh"

    async def async_press(self) -> None:
        await self.coordinator.async_request_refresh()

Press it from a dashboard card or use it in an automation and data updates instantly.

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How it works

This integration was built by reverse-engineering the official Hi-Mit II Android APK:

• RSA request signing — every API request is signed using RSA-PKCS1v15 with a 2048-bit public key embedded in the APK (assets/rsa_public_key.key). The server holds the private key and decrypts to verify.

• Password encoding — the login password is MD5-hashed (uppercase), then RSA-encrypted with a separate 512-bit key (assets/rsa_account_public_key.key).

• Temperature field mapping — actual live temperatures come from fixedDid16–19 fields (not obvious names), confirmed by tracing doSetCycle1Item / doSetCycle2Item in HeatPumpControllActivity.java:

  Field	Description
  fixedDid18	Circuit 1 actual water temp (tvTag333 in app UI)
  fixedDid19	Circuit 2 actual water temp (tvTag444 in app UI)
  fixedDid16	DHW actual water temp (tvTag111 in app UI)
  fixedDid17	Pool actual water temp (tvTag222 in app UI)

• Control — POST /himit-dshd/setDeviceProperty with a properties array of {cmdType, cmdValue} pairs. The sign covers all scalar fields plus the JSON-stringified properties array.

API endpoints

All on https://hmt-eu-gateway.hijuconn.com:

Method	Path	Purpose
POST	/account/acc/login_pwd	Login (auth-gateway)
POST	/account/acc/refresh_token	Refresh access token
GET	/himit-lgs/get_home_list	List homes
GET	/himit-dms/get_customer_device_list_info	List devices
POST	/himit-dshd/getDeviceProperty	Full device state
POST	/himit-dshd/setDeviceProperty	Send control commands

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File structure

custom_components/himit/
├── __init__.py          # Integration setup / teardown
├── api.py               # Async HTTP client (all crypto + API calls)
├── binary_sensor.py     # Read-only status sensors (A2W running)
├── config_flow.py       # UI login flow + home selection
├── const.py             # All constants (keys, field names, endpoints)
├── coordinator.py       # DataUpdateCoordinator — polling + token refresh
├── entity.py            # Shared base entity class
├── manifest.json        # HA integration manifest
├── number.py            # Temperature setpoint controls
├── sensor.py            # Temperature sensors
├── switch.py            # On/off switches
└── translations/
    └── en.json          # Config flow UI strings

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Requirements

• Home Assistant 2024.1 or newer
• Python packages (installed automatically): cryptography>=41.0.0, aiohttp>=3.9.0
• A valid Hisense / Hi-Mit II cloud account

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Disclaimer

This integration is not affiliated with or endorsed by Hisense. It was built by analysing the official mobile app for personal use. Use at your own risk.