DDSU666 Power Meter – Home Assistant Integration

Home Assistant integration for the 正泰 (CHNT) DDSU666 single-phase power meter. The meter is connected via RS485 Modbus; use a common RS485‑Modbus‑to‑TCP gateway so the meter is reachable over your LAN. This integration reads voltage, current, power, power factor, frequency, and total active energy, and exposes them as sensors. The total active energy sensor can be used in the Energy dashboard for consumption statistics.

Requirements

• Home Assistant 2025.x or 2026.x (tested on 2026.3.1 / HAOS 17.1)
• Modbus TCP gateway on the same network as Home Assistant (IP and port reachable)
• DDSU666 meter connected to the gateway and configured with a known Modbus slave address (default 1)

Installation

Via HACS (recommended)

1. In HACS, go to Integrations, click the three dots, then Custom repositories.
2. Add this repository URL and set category Integration.
3. Search for DDSU666 Power Meter, install it, then restart Home Assistant.

Manual

1. Download or clone this repository.
2. Copy the custom_components/ddsu666 folder into your Home Assistant custom_components directory.
3. Restart Home Assistant.

Configuration

1. Go to Settings → Devices & services → Add integration.
2. Search for DDSU666 or DDSU666 Power Meter.
3. Enter:
   • Host (IP address): IP of the Modbus TCP gateway (e.g. 172.16.33.254).
   • Port: TCP port (e.g. 9999 or 502).
   • Modbus slave address: Slave/unit ID of the meter (default 1).
4. Click Submit. The integration will test the connection; if it succeeds, the device and sensors are created.

Options (change connection or register addresses)

After the integration is added, you can change the gateway IP, port, slave address, or Modbus register addresses without removing it:

1. Go to Settings → Devices & services.
2. Find the DDSU666 Power Meter integration and open it.
3. Click Configure (or the device → Configure).
4. Update host, port, or slave and submit. A connection test is run before saving.

Register addresses: If your meter uses different Modbus addresses (e.g. another firmware or a similar model), you can set each register in the same Configure screen. Values are in decimal (e.g. 8192 for 0x2000). The default values match the standard DDSU666; leave them unchanged if you are not sure.

Multiple meters (same gateway)

If one Modbus TCP gateway has several DDSU666 meters (different slave IDs), add the integration once per meter:

1. Add the first meter with the gateway IP, port, and its slave address (e.g. 1).
2. Add integration again with the same IP and port but a different slave address (e.g. 2, 3).
3. Each entry becomes one device with its own set of sensors. You can rename devices in the device list for clarity.

Diagnostics

To help with connection or data issues:

1. Go to Settings → Devices & services.
2. Open the DDSU666 Power Meter integration, then open the config entry.
3. Click Download diagnostics (or use the three-dot menu on the device).

The downloaded JSON includes:

• config: Current host (IP may be partially redacted), port, and slave.
• last_update: Time of the last successful Modbus read (ISO format).
• last_error: Last error message if the most recent read failed; otherwise null.
• last_raw: Last successfully read sensor values (for comparison with the meter or manual).

Do not share full diagnostics (especially unredacted IPs) in public places.

Sensors (entities)

Entity	Description	Unit	Use in Energy
Voltage	Instantaneous voltage	V	—
Current	Instantaneous current	A	—
Active power	Instantaneous active power	W	—
Reactive power	Instantaneous reactive power	var	—
Apparent power	Instantaneous apparent power	VA	—
Power factor	Power factor	—	—
Frequency	Grid frequency	Hz	—
Total active energy	Cumulative active energy	kWh	Yes

In the Energy dashboard, add a consumption (or similar) and choose the Total active energy sensor for this device to track electricity usage.

Supported device

• Model: 正泰 DDSU666 (CHNT DDSU666) single-phase power meter
• Communication: Modbus RTU over RS485, exposed via a Modbus TCP gateway (e.g. RS485‑to‑TCP converter) on your network

Development and testing

Unit tests run locally (no Home Assistant required):

pip install -r requirements-dev.txt
pytest tests -v

• Mock tests: float parsing (_read_float_reverse), config/register map (const), and the read_holding_registers wrapper that adapts to different pymodbus APIs (device_id / unit / slave / client.params.unit). The full async_read_all flow is tested with a mock client.
• Real device test (optional): if the meter is reachable (e.g. at 172.16.33.254:9999), run pytest tests/test_real_meter.py -v -s to hit the real meter. Set DDSU666_HOST, DDSU666_PORT, DDSU666_SLAVE to override; set DDSU666_SKIP=1 to skip this test.

License

See LICENSE in the repository root.