Reference · built on requestConnectorIndustrial & building protocols

M-Bus

Heat, water, gas, and electricity meter readouts over wired or wireless M-Bus (EN 13757), through a level converter or gateway.

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About

M-Bus, the Meter-Bus, is the European standard for reading utility meters, published by CEN as the EN 13757 series. Wired M-Bus runs a master and up to 250 slaves on a two-wire cable at 300 to 9600 baud; the master signals with voltage and the meters answer with current, so meters can draw power from the bus. Wireless M-Bus, EN 13757-4, carries the same application layer over radio, and the Open Metering System specification builds on it with AES-128 security profiles.

Through Fibric, a connector polls meters through a level converter or gateway with REQ_UD2 and parses each RSP_UD record by its DIF and VIF fields. An operator watches consumption and proposes configuration changes for your approval.

This is a reference listing. It documents what Fibric would read from M-Bus and what it could propose, based on the vendor's published interfaces. Fibric builds it under a managed deployment when you request it; selecting it here installs nothing.

Inputs

  • Meter readings returned in RSP_UD telegrams, each record coded by a DIF for data type and length and a VIF for unit and multiplier
  • The fixed data header of each meter: identification number, manufacturer ID, version, medium, access number, status, and signature
  • Energy in Wh, volume in m3, temperature, and flow as the VIF tables code them
  • Application status from the status byte, including the busy and error bits
  • Meters discovered by secondary address, searching the 8-digit identification number with wildcard nibbles through address 253
  • Wireless M-Bus telegrams received by an OMS gateway, with physical and link layers per EN 13757-4

Proposed actions

  • Target capability: propose setting a meter's primary address with SND_UD, DIF 01h and VIF 7Ah, for your approval
  • Target capability: propose switching a meter's baud rate with CI codes B8h to BFh; the meter confirms with E5h at the old rate
  • Target capability: propose an application reset with CI 50h on a meter that stops answering

Proposed actions are target capabilities. Every action runs propose-first and needs a validated deployment and the appropriate permissions.

What you can build

  • Submeters that drift from the main meter

    Readouts from each heat or water meter are totaled per riser and compared with the main meter's register. The operator lists meters whose share moves and marks the ones with status errors.

    With Submeter Drift

  • Chargebacks from real registers

    Monthly deltas per meter identification number, in the units the VIF codes, feed a chargeback proposal per tenant with the readings attached.

    With Utility Chargeback

  • A leak that shows at 3 a.m.

    Water flow that never returns to zero overnight is read from the meter's flow record. The operator raises it with the meter's location and proposes a work order.

    With Leak Response

  • Reconcile the utility bill

    Register deltas over the billing period are set beside the invoiced quantity. Gaps larger than your tolerance are flagged with the readings that support them.

    With Bill Reconcile

Requirements

  • A level converter or gateway that acts as the M-Bus master and is reachable over serial or IP from where the connector runs
  • Primary addresses from 1 to 250 assigned, or the identification number, manufacturer, version, and medium of each meter for secondary addressing
  • Bus segments within 350 m from meter to master and 1000 m of total cable, with a repeater beyond that
  • For wireless meters, an OMS gateway holding the meters' AES keys
Authentication
Wired M-Bus has no authentication of its own, so access is the level converter's or gateway's credentials; wireless M-Bus under OMS encrypts with per-meter AES-128 keys in security profiles A through D.

Limits

  • Wired M-Bus is half duplex and master initiated; a meter only answers a request and cannot report on its own
  • Each response carries at most 252 bytes of user data, so a bus of many meters is read in sequence
  • The m-bus.com documentation reflects the specification of the late 1990s; the current EN 13757 parts are sold by standards bodies
  • Manufacturer-specific VIF codes 7Fh and FFh carry data the standard tables cannot decode

Access and pricing

Reference listing. Fibric builds the connector under a managed deployment when you request it. Your quote covers the build, capabilities, usage, and support.

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Questions and answers

How many meters fit on one M-Bus?
The physical layer documentation states a maximum of 250 slaves per segment, addressed 1 to 250. Address 253 selects a meter by secondary address, 254 broadcasts with replies, and 255 broadcasts without replies. Repeaters extend a segment beyond 350 m.
How is a reading decoded?
A RSP_UD telegram holds a fixed data header and data records. Each record starts with a DIF that gives the data type and length, then a VIF that gives the unit and multiplier, then the value. Numbers are often BCD coded.
Is wireless M-Bus encrypted?
Under the Open Metering System specification, yes. Security profile A uses AES128-CBC, profile B adds an 8-byte CMAC, profile C uses TLS 1.2, and profile D uses AES128-CCM. Profiles B, C, and D also require a message counter.
Ask about M-Bus

Ask about the capabilities and requirements in this listing.

For project-specific requirements, contact Fibric.

This connector listing is developed, published, and supported by Fibric. It describes integration with M-Bus through published interfaces. Third-party names and logos identify the systems an integration connects to; they are the property of their respective owners, who are not affiliated with Fibric and do not sponsor or endorse this listing. Trademark policy