ESPHome OpenDTU to SDM630 Component

ESPHome external component that reads Hoymiles microinverters data from OpenDTU and presents it to a hybrid inverter as a Modbus RTU Eastron SDM630 energy meter.

Note: It was developed and tested with Deye, but any Modbus master expecting an Eastron SDM630 (another hybrid inverter, EMS, or data logger) may work if it uses the same register map.

Why this project exists

This component was built for Deye 3-phase hybrid inverters in AC Couple on Load Side mode - when additional Hoymiles microinverters inject PV on the load side, separate from the inverter's own MPPT strings.

In that mode Deye needs an Eastron SDM630 to measure how much power the microinverters inject into the installation. The inverter uses those per-phase values to separate AC-coupled PV generation from grid import/export and to calculate household load correctly. A physical meter is installed on the AC conductors where the microinverter system ties into the grid, with readings delivered over the Meter-485 Modbus port.

Instead of mounting that physical SDM630 on the AC cabling, this bridge:

• Uses OpenDTU for wireless communication with Hoymiles microinverters - no RS485 or extra meter wiring across the site
• Aggregates AC-coupled PV from many microinverters at different coupling points into one emulated SDM630 - Deye exposes only one Eastron meter interface on Meter-485, so you cannot wire a separate meter at each distant feed-in. OpenDTU radio reach plus this bridge can still combine them
• Reads live data from OpenDTU over WebSocket (/livedata) as often as OpenDTU publishes it (up to once per second, depending on the OpenDTU poll interval)
• Maps each microinverter to the correct grid phase (L1/L2/L3)
• Exposes the result as an SDM630 Modbus slave on the Deye Meter-485 port

That lets Deye meter AC-coupled PV generation and calculate household load correctly - without affecting OpenDTU operation. OpenDTU continues to poll and manage all microinverters as before, this bridge only subscribes to the livedata stream. Frequent livedata updates (up to once per second) keep instantaneous power and energy counters aligned with the microinverters. Without correct coupled-PV metering, household load can read as negative or no consumption at all while microinverters are producing - on some Deye firmware/settings negative values are simply clamped to zero rather than displayed.

How it works

flowchart TB
  subgraph feed_l1 ["Grid feed-in L1"]
    mi_l1["MI HMS shed"]
  end
  subgraph feed_l2 ["Grid feed-in L2"]
    mi_l2["MI HMS fence"]
  end
  subgraph feed_l3 ["Grid feed-in L3"]
    mi_l3a["MI HMS garage"]
    mi_l3b["MI HMS roof"]
  end
  odtu["OpenDTU ESP32"]
  bridge["OpenDTU to SDM630 ESP32"]
  deye["Deye hybrid inverter"]
  mi_l1 -->|RF| odtu
  mi_l2 -->|RF| odtu
  mi_l3a -->|RF| odtu
  mi_l3b -->|RF| odtu
  odtu -->|WebSocket livedata| bridge
  bridge -->|Modbus RTU SDM630| deye

Loading

Each microinverter (MI) only needs radio reach to OpenDTU. The bridge sums per-phase active power and current from every mapped inverter into the single SDM630 register image that an inverter polls.

• Parses OpenDTU livedata JSON (inverters[].AC["0"] → voltage, current, power, frequency)
• Maps microinverters to grid phases via microinverter_map (several inverters can share a phase, current and power are summed)
• Inverts current and power sign (OpenDTU reports positive generation, the SDM630 presents export as negative values)
• Serves the full SDM630 input register buffer on slave_address (0x02 for Deye Grid Tie Meter 2), silently ignores Deye queries to 0x01 (main meter address)

Requirements

Current scope: Only single-phase Hoymiles microinverters managed by OpenDTU are supported at this time.

• OpenDTU running and reachable on your network (WebSocket /livedata, dashboard password), with single-phase Hoymiles microinverters
• A second ESP32 for this bridge (separate from the OpenDTU ESP32 in the tested setup)
• RS485-to-TTL converter (no DE/RE pin required in the tested setup)
• ESPHome ≥ 2025.6.0
• Modbus master (e.g. Deye hybrid inverter with Grid Tie Meter 2 / Eastron type) reading Eastron SDM630 over Modbus RTU (9600 8N1)
• Home Assistant is not required - ESPHome alone is enough to build, flash, and run this component

Tested setup

Layer	Details
OpenDTU	tbnobody/OpenDTU v26.3.30, Poll Interval 1 s (DTU Settings), on ESP32 DevKit V1
Microinverters	Hoymiles HMS-2000-4T and HMS-1600-4T, each on a separate grid phase (3-phase supply)
Deye inverter	SUN-12K-SG04LP3-EU, firmware 1172, Grid Tie Meter 2 enabled, energy meter type Eastron (Advanced Settings), polls Grid Tie Meter 2 at fixed address 0x02
This bridge	ESP32 DevKit V1, RS485-to-TTL auto-direction converter, slave_address: 0x02 to match Deye Grid Tie Meter 2

Deye uses fixed Modbus slave addresses - they are not configurable in the inverter menu:

Address	Role
0x01	Main / grid energy meter
0x02	Grid Tie Meter 2 (AC-coupled PV measurement)

For AC Couple on Load Side with Grid Tie Meter 2 enabled, Deye polls 0x02 for per-phase power and energy from the coupled microinverter system. The emulated meter must answer on that address - Deye does not allow choosing a different slave ID. Deye may also scan 0x01 for the main grid-side meter.

Wiring

flowchart LR
  subgraph esp32 ["ESP32 DevKit V1"]
    TX["GPIO17 TX"]
    RX["GPIO16 RX"]
    VCC["3V3"]
    GNDesp["GND"]
  end
  subgraph conv ["RS485 to TTL auto-direction"]
    TXD["TXD"]
    RXD["RXD"]
    VCCc["VCC"]
    GNDc["GND"]
    Aterm["A"]
    Bterm["B"]
  end
  subgraph inv ["Deye Meter-485 RJ45"]
    RS485Pin2["Pin 2 orange - METER-485-A"]
    RS485Pin1["Pin 1 white-orange - METER-485-B"]
  end
  TX --> TXD
  RX --> RXD
  VCC --> VCCc
  GNDesp --> GNDc
  Aterm -->|orange wire| RS485Pin2
  Bterm -->|white-orange wire| RS485Pin1

Loading

Connect the inverter with a standard twisted pair. From the RS485 converter, use only A (orange) and B (white-orange) to the inverter Modbus terminals. Connect ESP32 GPIO17 → TXD, GPIO16 → RXD, 3V3 → VCC, GND → GND on the converter. Some modules label the same pins DI/RO instead of TXD/RXD.

The tested setup uses an auto-direction module - no flow_control_pin needed. If your converter requires DE/RE control, uncomment and set flow_control_pin under the modbus: block in your YAML.

Configuration reference

All options under opendtu_sdm630::

Option	Required	Default	Purpose
host	yes	-	OpenDTU IP address or hostname
password	yes	-	OpenDTU dashboard password (!secret)
modbus_id	yes	-	ESPHome modbus: hub ID (role: server)
microinverter_map	yes	-	Map microinverters to grid phases
port	no	80	OpenDTU HTTP port
path	no	/livedata	WebSocket path
username	no	admin	WebSocket authentication username
slave_address	no	0x02	Modbus slave address of the emulated SDM630
data_timeout	no	15s	Stale-data threshold before fallback values are used
default_voltage	no	230.0	Fallback voltage per phase [V]
default_frequency	no	50.0	Fallback grid frequency [Hz]
publish_sensors	no	true	Publish ESPHome entities for monitoring

microinverter_map

Each entry requires grid_phase (1 = L1, 2 = L2, 3 = L3) and exactly one identifier:

• serial - microinverter serial from OpenDTU livedata (inverters[].serial), stable if you rename the inverter in OpenDTU
• name - microinverter name from OpenDTU livedata (inverters[].name)

serial and name cannot be used in the same entry.

grid_phase is the installation phase (L1/L2/L3) where that microinverter's AC output contributes to coupled PV. Multiple microinverters on the same phase: active current and power are summed, voltage is averaged. Grid frequency is averaged across mapped microinverters, if unavailable, default_frequency is used.

Example:

opendtu_sdm630:
  host: 192.168.1.50
  password: !secret opendtu_password
  modbus_id: modbus_1
  slave_address: 0x02
  microinverter_map:
    - name: "Garage-HMS-2000-4T"
      grid_phase: 1
    - serial: "123456789012"
      grid_phase: 2

Auto-created entities

When publish_sensors: true (default), the component registers:

• L1/L2/L3 voltage, current, and power sensors
• Total power and frequency sensors
• WebSocket Status and WebSocket Data Valid (diagnostic binary sensors)
• Board Restart button and Component Version text sensor (diagnostic)

Set publish_sensors: false if you only need Modbus output and no Home Assistant entities.

Individual sensor names and options can be overridden inside the opendtu_sdm630: block.

Failsafe behaviour

When the WebSocket disconnects, JSON parsing fails, or no fresh data arrives within data_timeout, the bridge reports zero coupled PV - active power and current on all phases are set to 0.0. Voltage falls back to default_voltage and frequency to default_frequency. Phases without a mapped microinverter always report 0.0 for power and current.

Modbus registers

Active input registers (FP32, high word first). All other addresses return 0.0.

Address	Value
0x0000	Voltage L1 [V]
0x0002	Voltage L2 [V]
0x0004	Voltage L3 [V]
0x0006	Current L1 [A]
0x0008	Current L2 [A]
0x000A	Current L3 [A]
0x000C	Active Power L1 [W]
0x000E	Active Power L2 [W]
0x0010	Active Power L3 [W]
0x0034	Total Active Power [W]
0x0046	Frequency [Hz]

secrets.yaml

1. Copy secrets.yaml.example to secrets.yaml in the same directory as your ESPHome YAML.

2. Fill in the four keys:

   wifi_ssid: "YourWiFiSSID"
   wifi_password: "YourWiFiPassword"
   opendtu_password: "OpenDTUDashboardPassword"
   ota_password: "OTAPasswordForDevice"

3. Reference secrets in your YAML with !secret, for example password: !secret opendtu_password.

Never commit secrets.yaml - it is listed in .gitignore.

Using opendtu_sdm630.yaml

opendtu_sdm630.yaml is a reference configuration and a practical starting point. In most cases you will:

• Copy it as-is and adjust host, microinverter_map, and UART pins for your installation, or
• Merge its opendtu_sdm630:, uart:, and modbus: sections into an existing ESPHome device config.

The reference file pulls the component from GitHub:

external_components:
  - source: github://Lewa-Reka/esphome-opendtu-to-sdm630@main
    components: [opendtu_sdm630]

It also includes WiFi, OTA, API, UART (TX=17, RX=16, 9600 baud), Modbus server, and optional diagnostic sensors. You only need to add or change what differs on your site.

For local component development, point external_components to a local path instead:

external_components:
  - source:
      type: local
      path: components
    components: [opendtu_sdm630]

Installation

Home Assistant is optional. You only need ESPHome to compile, flash, and update the firmware.

Method 1: Home Assistant ESPHome add-on

1. Install the ESPHome add-on from the Home Assistant add-on store and open the dashboard.
2. Click + New Device, name the device, select ESP32, and skip the template wizard.
3. Create secrets.yaml in your ESPHome config directory (see above).
4. Edit the new device and replace its content with opendtu_sdm630.yaml, adjusted for your network and microinverters.
5. Click Install, connect the ESP32 via USB, select the serial port, and flash.
6. Wire the RS485 converter to the Deye Modbus port and power the ESP32.

The device will run independently of Home Assistant. HA is only used here as a convenient ESPHome UI.

Method 2: ESPHome CLI

pip install esphome
cp secrets.yaml.example secrets.yaml   # edit before flashing
esphome run opendtu_sdm630.yaml

Useful follow-up commands:

esphome compile opendtu_sdm630.yaml
esphome upload opendtu_sdm630.yaml
esphome logs opendtu_sdm630.yaml

OTA updates work through the ESPHome dashboard or esphome upload over the network after the first flash.

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Copyright Notice

Copyright 2026 Lewa-Reka <lewareka.yt@gmail.com>

Licensed under the Apache License, Version 2.0 (the "License"),
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Third-Party Components

This project uses ESPHome and related components. Please refer to the NOTICE file for additional license information.