Modbus TCP

Supported devices

The following smart-me devices support Modbus TCP:

• 3-phase meter telstar

• 3-Phase Meter Telstar CT

• Pico EV-Charger

Limitations

It is not possible to assign a fixed IP address. If this is desired, this setting must be made on the router. The MAC address of the individual devices is not known to smart-me. This can be determined using the instructions below.

Queries should not be made more frequently than every 2 seconds. Increasing the polling frequency can lead to unanswered polls in certain constellations. The device cannot be damaged if the polling interval is < 2 seconds.

Specific information about Pico and Modbus TCP

Modbus TCP can be used with the Pico if:

1. The Pico is not in a load management group.

2. The Pico is in a load management group and the master (determined automatically).

Modbus TCP is deactivated for all slaves in a load management group, as they also do not have their own IP-address. If the Picos in a load management group want to be read or controlled, we recommend to use the Rest API. 

Find the address of the device

The Modbus register of a smart-me device can be read out via DNS or IP address. 

• DNS can be activated in the portal.

• The IP address is assigned by the local DHCP server. The IP address can be determined using the instructions below.

A public IP address or the internal IP address of the device can be selected as the IP address:

Internal IP

This is the local IP address of the smart-me device. This can be used if you are in the same network.

Public IP

The public IP address is used. This is normally the IP address of your router.

Background information

With the dns-me service, it is possible to connect directly to a smart-me device without knowing its IP address. If the DNS address is activated for a smart-me device, its local or public IP address is automatically assigned to a DNS name (e.g. smart-me_123456.dns-me.com).

smart-me uses the dns-me.com service for this.

Determine IP address directly on the router

smart-me does not know the MAC address of the individual devices. Determining the IP address without first activating the DNS service is therefore more complicated. One option is to query all IP addresses with Modbus TCP to check which serial number is returned in response.

Data transmission

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)

Example Modbus

Example with: https://www.modbusdriver.com/modpoll.html

Change Pico Loadmanagement

modpoll.exe -r 0x206E -t 4:int -i -1 -m tcp -p 502 192.168.178.63 16000