How the gateway works
Meters, inverters and other devices with an RS-485 interface mostly speak Modbus RTU. The M-Center has two RS-485 ports for two Modbus RTU lines and reads up to 64 devices through them.
The M-Center then publishes the values to your MQTT broker, locally or in the cloud, with its own topic per device and register, optionally with TLS.
The values read are available via MQTT regardless of the storage setting. In addition, the M-Center stores the registers with «Save in database» enabled in its internal 16 GB memory.
How the devices get into the M-Center
- Connect the devices in a line to one of the two RS-485 lines of the M-Center and terminate the cable at both ends.
- Add the device in the web interface: choose the line, enter the serial number and the Modbus slave address.
- Set baud rate, data bits, parity and stop bit as on the device, plus byte and word order.
- Apply a Modbus driver or create registers: start address (from 1), function code 03 or 04, data type, unit, divisor and OBIS code.
- Activate MQTT: enter broker, port, user and password, prefix, TLS and QoS.
Newly created Modbus registers are not saved automatically. First check that the value is correct, then enable «Save in database». Modbus drivers can be exported as JSON and transferred to other M-Centers.
How the topics are structured
<prefix>/emu/mcenter/<MAC M-Center>/meterreading/<serial number>/byregister/<register number>
<prefix>/emu/mcenter/<MAC M-Center>/meterreading/<serial number>/byobis/<OBIS code>The serial number in the topic is the number you enter when creating the Modbus device, so choose it uniquely. For topics by OBIS code, enter the OBIS code for the registers; active energy import, for example, is then under the same topic ending for every device.
Check the messages with an MQTT client such as MQTT Explorer before processing them further.
Order numbers
| Article number | Description | Shop |
|---|---|---|
| 210.000.00 | EMU M-Center for 20 M-Bus devices | Shop: EMU M-Center 210.000.00 → |
| 210.200.00 | M-Center | Licence RS485 32 devices | |
| 210.200.01 | M-Center | Licence RS485 64 devices | |
| 210.300.03 | M-Center | Licence MQTT |
Order online in the EMU Metering shop.
Licences can be activated later at any time, without changing hardware. M-Bus, RS485, Modbus TCP and all output interfaces run in parallel.