What B-GW Is
A BACnet device profile is a standardized capability level: a checklist of things a device must be able to do before it can wear the label. B-GW (BACnet Gateway) is defined in Annex L of ANSI/ASHRAE 135-2024 (clause L.7.2) as a device that presents devices or data from a non-BACnet system as BACnet objects, so a BACnet building system can read and write them as if they were native.
It is a Miscellaneous-family profile, so a device can claim it alongside a profile from another family. This is the profile behind protocol-conversion products: a device that speaks Modbus, LonWorks, M-Bus, or another protocol on one side and exposes that data as BACnet objects on the other. The checklist items are BACnet Interoperability Building Blocks (BIBBs); a device documents its claim in its PICS (Protocol Implementation Conformance Statement).
Where It’s Used
B-GW is the profile for the gateway box that brings a non-BACnet system onto a BACnet network.
- Protocol conversion. A gateway mapping Modbus registers or M-Bus meter data into BACnet objects the BMS reads like any other point.
- Legacy integration. Presenting an older proprietary control system as BACnet without replacing it.
- Multi-protocol front ends. A device aggregating several field protocols and exposing a single BACnet interface upstream.
Required Services
The table below is the service set required by the B-GW BIBBs. Initiates means the device sends the request or notification; Executes means the device receives and acts on it (responding, for confirmed services). BIBB codes encode the same split: a -A BIBB is the initiating side, a -B BIBB the executing side. A - means the profile does not require that direction; a device may still support it.
| Capability area | Service | Required by BIBB | Initiates | Executes |
|---|---|---|---|---|
| Data sharing | ReadProperty | DS-RP-B | - | Yes |
| Data sharing | WriteProperty | DS-WP-B | - | Yes |
| Device and network management | Who-Is | DM-DDB-B | - | Yes |
| Device and network management | I-Am | DM-DDB-B | Yes | - |
| Device and network management | Who-Has | DM-DOB-B | - | Yes |
| Device and network management | I-Have | DM-DOB-B | Yes | - |
| Device and network management | DeviceCommunicationControl | DM-DCC-B | - | Yes |
The defining requirement is how the gateway models the other system. B-GW additionally requires one of two gateway BIBBs: GW-EO-B, which presents the mapped points as BACnet objects on the gateway’s own Device object, or GW-VN-B, which presents the mapped devices as a virtual BACnet network behind the gateway. Both build on the ReadProperty and WriteProperty services above; the choice is about whether downstream devices appear as objects or as a network of virtual devices.
Related Profiles
| Profile | How it relates to B-GW |
|---|---|
| B-RTR | Router: forwards native BACnet traffic between networks, whereas a gateway translates a non-BACnet system into BACnet |
| B-BBMD | Broadcast Management Device: an IP-broadcast function, often present on the same gateway hardware |
| B-BC | Building Controller: a common base profile to stack the gateway function onto |
What Chipkin Provides
The CAS BACnet Stack implements both gateway BIBBs (GW-EO-B embedded objects and GW-VN-B virtual network) and the device-management services the profile requires; presenting non-BACnet systems as BACnet is a core use of the stack and the QuickServer platform. Talk to us about building or integrating a B-GW device on the stack.