Modbus TCP

Requirements

To activate Modbus TCP you need a smart-me Professional subscription

With Modbus TCP, the measured values of a device can be queried directly via the network connection. No detour via the cloud is necessary.

Supported devices

The following smart-me devices support Modbus TCP:

3-phase meter telstar all versions

Kamstrup module from firmware version 8.0 (Info: This module cannot offer stable Modbus communication without a constant Internet connection.)

Activate Modbus TCP

  1. Log in on the smart-me website or in the smart-me app.

  2. Select the desired device

  3. Click on "edit"

  4. Switch on "Modbus TCP" under the "Advanced Settings"

Find the address of the device

To read a device with Modbus TCP, you need to know the address of this device. The smart-me devices obtain the IP address from the local DHCP server. There are two ways to find the address:

  1. Enable DNS:
    The easiest way to connect to a smart-me device in the local network is to enable the automatic DNS update. More information: Dynamic DNS

  2. Configure DHCP / Router Server:
    Another way to find out the IP address of a smart-me meter is to look it up on your router or DHCP server. Search for an entry with a MAC address which begins with "D0 :".

Modbus TCP Protokoll

TCP Port: 502

Functions

The smart-me Meter supports the following Modbus functions:

  • Read Holding Register (Code 03)

Register Addressing

For historical reasons the address in Modbus is 1 lower than the internal register address. So the start address has to be (Registeraddress - 1)

Register Addressing

Example Modbus Telegram (read serial number)


Request: 00 04 00 00 00 06 01 03 1F FF 00 02

Response: 00 03 00 00 00 07 01 03 04 00 00 18 9F