Modbus ⇄ BACnet gateway

Need to connect Modbus and BACnet? The Weble WBox routes Modbus ⇄ BACnet natively: one gateway speaks both protocols and maps data points in real time — no PC, no middleware, no cloud dependency.

The protocols

Typical use case

One of the most common retrofits: the BMS speaks BACnet/IP, but chillers, heat-meters, variable-speed drives, inverters and PLCs on site only speak Modbus. Replacing them is out of the question. The WBox integrates that field equipment into the BMS so it shows up as native BACnet — read and written from existing graphics, schedules and trends — and you extend an existing supervision system instead of bolting a second one beside it.

In the field

Weble customers run this routing in production:

How the WBox bridges Modbus and BACnet

Activate the BACnet and Modbus drivers. Modbus holding and input registers map to BACnet objects: measurements to Analog Input/Value, states and commands to Binary Input/Value. The WBox handles scaling, word and byte order, and signed values per register, and exposes the result as discoverable BACnet objects — no per-point setup on the BMS side. Writes from BACnet propagate to Modbus holding registers, and a JavaScript step can clamp, scale or combine values before they cross.

Example mapping

Capacity & limits

• Modbus — Modbus addresses up to 247 slaves per line (RTU or TCP) — about 32 RTU devices per RS-485 segment before a repeater.
• BACnet — BACnet/IP scales to large object counts; BACnet MS/TP carries up to 127 master nodes per segment.

On the WBox, a driver licence enables the whole protocol — there is no artificial per-point tier to unlock. Capacity scales with the gateway model, from the compact S103 to the E413: you are bounded by the field bus, not by your licence.

Frequently asked questions

What you need

One WBox gateway with these two driver licences:

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