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Version: 1.25.0

Connect Modbus TCP/Serial devices (PLCs, meters, inverters)

Modbus is everywhere in industrial and energy hardware - PLCs, energy meters, solar inverters, HVAC controllers. This tutorial shows how to connect Modbus devices to OpenRemote running as a gateway, using the native Modbus agent, mapping registers straight onto asset attributes over Ethernet (Modbus TCP) or serial (Modbus Serial).

Why this matters for OEMs and integrators

The Modbus agent runs inside the OpenRemote Manager - there is no separate gateway application to deploy and operate just to speak an industrial protocol. The same is true for KNX, and SNMP and more, which keeps your industrial IoT architecture simple.

Prerequisites​

  • A running OpenRemote instance - see the Quick Start.
  • A reachable Modbus device: a Modbus TCP slave on your network, or a Modbus RTU device on a serial line accessible to the Manager host.
  • The device's register map (function code, address, data type, scaling).

Step 1 - Create a Modbus agent​

  1. On the Assets page, click + and add a Modbus TCP Agent (or Modbus Serial Agent).
  2. For TCP, set the host/IP, port and the unit/slave ID.
  3. For RTU, set the serial port, baud rate, parity and stop bits, and the unit ID.

See the Modbus agent reference for all parameters.

Step 2 - Create the asset that represents the device​

Create an asset (e.g. an ElectricityMeter or a generic Thing) and add attributes for each value you want to read or write - for example power (Number), voltage (Number), relayState (Boolean).

Step 3 - Link attributes to Modbus registers​

For each attribute, add the Agent Link configuration item and select your Modbus agent, then specify:

  • the register type (coil, discrete input, input register, holding register),
  • the address,
  • the data type (e.g. INT16, UINT32, FLOAT32),
  • the read/write behaviour and a polling interval,
  • the unit ID
note

Writing to a holding register or coil lets you actuate the device (e.g. toggle a relay) straight from an attribute write, the Manager UI, the REST API, or a rule.

Step 4 - Verify live data​

  1. Open the asset and confirm attribute values update on each poll.
  2. After adding the Store data points configuration item to an attribute, the History panel shows attribute values over time.
  3. Test a write by changing a writable attribute and confirming the device responds.

Step 5 - Turn raw values into insight​

Use Flow rules to derive virtual attributes (e.g. compute energy from power), and When-Then rules to alarm on thresholds.

Next steps​