Babel Buster BB3-3101 Modbus to BACnet Gateway

Control Solutions’ Babel Buster® BB3-3101 is a BACnet MS/TP client/server device that functions as a Modbus RTU master/slave. A large number of BACnet objects gives you flexibility in mapping Modbus registers to any combination of BACnet objects. Packed Modbus registers may be parsed to multiple BACnet objects when reading. Multiple BACnet objects may be packed into a single Modbus register when writing. All standard Modbus register types are supported.

Input objects will poll their assigned Modbus register at the interval you specify, and provide the Modbus data as the Present Value when read. Commandable Output objects are used to write Modbus registers, and will update the Modbus device each time BACnet is updated. The BB3-3101 supports over 1,000 commandable or non-commandable objects.

Value objects will poll their assigned Modbus register at the interval you specify. The content of the Modbus register will be given as the Present Value of the BACnet object when read. The Modbus register is written each time the BACnet Value object is written. The Value object corresponds to the Modbus Holding register.

The BB3-3101 is most often used as a Modbus master, but it can operate as a slave while MS/TP operates as a client (master). This makes it possible to put MS/TP devices on a Modbus network (but does still require an understanding of BACnet). MS/TP data in remote devices is queried and saved locally. The local data may then be accessed by another Modbus master.

The BB3-3101 configuration tool connects to the MS/TP network using the MTX002 MS/TP to USB adapter (if not using a BACnet IP router). This intelligent adapter plugs into your PC's USB port, and offloads the MS/TP token passing from the PC to make it more reliable. The MTX002 allows you to connect your PC to an MS/TP network running at 76800 baud, something not possible with a generic RS-485 port adapter.

The MTX002 functions as an MS/TP device itself. The combination of the MTX002 and configuration tool running on your PC will appear on the network as a discoverable BACnet device. The diagnostic pages in the configuration tool can be used to read and write any objects in any MS/TP device on the network. The configuration pages provide templates for reading and writing the multiple properties per BACnet object that define its Modbus mapping. All configuration parameters exist as properties of BACnet objects which are accessible to any BACnet client. The Control Solutions configuration tool simpy provides a user friendly template for accessing those properties.

The BACnet Gateway Configuration Tool is the most user friendly BACnet gateway configuration tool to date. Connect the gateway to your laptop via a USB to MS/TP adapter (MTX002) or via a BACnet IP router.

Import Modbus register lists formatted as CSV files. Create your register list using any standard spreadsheet program, save as CSV, then import. The tool will then automatically create and assign BACnet objects. You can also start with a BACnet object list, saved as a CSV file, and import the object list. The tool will automatically assign Modbus registers. Or you can specify the complete mapping of BACnet objects to Modbus registers in a CSV file and import that.

You do not need to start with a CSV list. The user friendly tool provides templates to build a complete configuration from scratch. The configuration tool also provides the means to allocate the gateway's object pool to Analog, Binary, or Multi-state type objects, as Inputs, commandable Outputs, or Value objects.

Isolated Modbus Port Option Available

Troublesome ground loops can be created when the Modbus network and MS/TP network ground points are connected together. This loop is broken by using isolated transceivers. The standard BB3-3101 provides 500V isolation between the MS/TP port and gateway common. The gateway power/ground and Modbus port share a common ground.

The BB3-3101-ISO provides additional optional isolation of the Modbus port. There is then 3-way isolation. Both MS/TP and Modbus RTU are isolated from each other and from the power supply input of the BB3-3101-ISO. If the gateway will be powered from a supply that is common to other MS/TP devices, then you will want to use the BB3-3101-ISO so that Modbus RTU is isolated from MS/TP.

BB3-3101 Features

• Read/Write Modbus registers via BACnet objects
     • 1024 BACnet objects, commandable or non-commandable
     • Object allocations are user configurable
• AI, AO, AV, BI, BO, BV, MSI, MSO, MSV objects
• State text string support for binary, multistate objects
• COV subscription support
• BACnet slave is Modbus RTU master or vice versa
• Bidirectional communication between BACnet and Modbus
• Supports Modbus “coils”, input registers, holding registers
• Single or double Modbus registers
• Signed, unsigned, IEEE 754, single bit
• Modbus register mapping configured via object properties
• Modbus registers may be scaled
• Modbus (master) polling interval configurable per point
• Commandable BACnet objects implement priority array
• Standard Isolated EIA-485 transceiver for MS/TP
• Standard Hardened EIA-485 transceiver for Modbus RTU
• Optional Isolated EIA-485 transceiver for Modbus RTU
• Optional EIA-232 transceiver for Modbus RTU
• MS/TP baud rates: 9600, 19200, 38400, 76800
• Modbus RTU baud rates: 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200
• Powered by 10-30VDC or 12-24VAC 50/60 Hz
• Power Consumption: 0.1A @ 24VDC
• DIN rail mounting, 100mm H x 70mm W x 60mm D
• Pluggable screw terminal blocks
• Operating temperature -40°C to +85°C
• Humidity 5% to 90% non-condensing
• Listed to UL 916 and (Canadian) C22.2 No. 205-M1983
• BTL Certified, FCC, CE Mark