Products/M-Center/RS485 to BACnet IP

M-CenterApplication

RS485 (Modbus RTU) to BACnet IP: gateway with the EMU M-Center

The EMU M-Center reads devices with RS485 (Modbus RTU) and makes their values available to the building management system as BACnet IP devices. No PC in between, in parallel with M-Bus meters and other interfaces.

Key facts

  • Two RS-485 lines, up to 64 Modbus RTU devices depending on the licence (32 or 64).
  • Per device: serial number, slave address, baud rate, parity, stop bit, byte and word order.
  • Each device becomes its own BACnet device object with its own instance number.
  • B-ASC certified, BBMD for access across subnets.
  • Required: M-Center base unit plus licence 210.200.00 or 210.200.01 and licence 210.300.00.
2885.6Professional II RS485Slave 1 · SN 22231100
1412.3Professional II RS485Slave 2 · SN 22231101
3207.9Professional II RS485Slave 3 · SN 22231102
EMU M-CenterModbus RTU master · BACnet IP · 10:2C:EF:02:6C:B9
EMU M-CenterModbus RTU master
Register 6000 · active energy import
Slave 1SN 22231100–
Slave 2SN 22231101–
Slave 3SN 22231102–
BACnet building managementBACnet/IP · UDP 47808
Values in the BMS
Device 1001AI 1 · Import total–
Device 1002AI 1 · Import total–
Device 1003AI 1 · Import total–
Modbus RTU request

The M-Center queries each Professional II on the RS-485 line: slave address, function code 03, register 6000. The meter replies with its meter reading.

Simplified illustration. Serial numbers, addresses and values are examples. In operation, the M-Center reads every 15 minutes by default.

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 provides each device in BACnet as its own device object and the measured values as analog input objects. The M-Center is B-ASC certified and supports BBMD.

The values read are available via BACnet IP 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

  1. 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.
  2. Add the device in the web interface: choose the line, enter the serial number and the Modbus slave address.
  3. Set baud rate, data bits, parity and stop bit as on the device, plus byte and word order.
  4. Apply a Modbus driver or create registers: start address (from 1), function code 03 or 04, data type, unit, divisor and OBIS code.
  5. Activate BACnet IP: set the D-Net number, port and device instance of the M-Center and assign a BACnet instance number to each device.

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.

BACnet IP settings

  • D-Net number, port and device instance of the M-Center
  • Instance number per device, in the device under «BACnet IP»
  • BBMD enabled: access via the BBMD devices entered, using the two-hop broadcast method
  • Continuous reading: the M-Center reads the devices continuously so that the values in BACnet are as current as possible

With «Continuous reading», only the values at the time of the reading interval are stored. BACnet and the other interfaces receive continuously updated values in between.

Order numbers

Article numberDescriptionShop
210.000.00EMU M-Center for 20 M-Bus devicesShop: EMU M-Center 210.000.00 →
210.200.00M-Center | Licence RS485 32 devices
210.200.01M-Center | Licence RS485 64 devices
210.300.00M-Center | Licence BACnet IP

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.

Frequently asked questions

How many RS485 devices does the M-Center read?

Up to 64 Modbus RTU devices on two lines. Licence 210.200.00 covers 32 devices, 210.200.01 covers 64 devices.

Is the M-Center BACnet certified?

Yes, as a B-ASC (BACnet Application Specific Controller). With BBMD, the building management system reaches the M-Center from another subnet as well.

Can I use M-Bus, RS485 and Modbus TCP at the same time?

Yes. All devices appear in the same device lists, and the M-Center provides their values simultaneously via all licensed interfaces, such as BACnet IP, MQTT, Modbus TCP or OPC UA.

How often does the M-Center read the devices?

Every 15 minutes by default. You can choose from 15 minutes to 28 days, also per device.

Read more

SEITEEMU M-CenterProduct SEITEM-Bus to BACnet IPApplication SEITERS-485 / Modbus RTUBasics and bus layout SEITECommissioning the M-CenterGuide

Implementing RS485 to BACnet IP?

Send us the device list with manufacturer and type. We check the registers and name the licences.

Contact us

Phone
+41 (0)41 545 03 00

Technical support
helpdesk [at] emuag.ch
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