Introduction to PI Connector for BACnet

PI Connector for BACnet (Building Automation and Control Networks) records data from BACnet/IP compliant devices (such as HVAC equipment) to the PI System. The connector models an installation by creating the elements in PI Asset Framework (PI AF) and PI points in Data Archive, then populates the PI AF elements and PI points with data sent from the source devices.

BACnet is a communication protocol that is developed and maintained by ASHRAE. The connector adheres to ANSI/ASHRAE Standard 135-2012.

PI Connector for BACnet communicates with any device using BACnet/IP, and devices that conform to other BACnet protocols using a BACnet gateway or router. The BACnet devices and routers do not need to be on the same subnet as the connector. A sample hardware diagram is illustrated below:

Sample hardware diagram

Currently, the connector supports the following BACnet object types:

• Accumulator

• Analog input

• Analog output

• Analog value

• Binary input

• Binary output

• Binary value

• Device

• Multi-state input

• Multi-state output

• Multi-state value

Operational overview

When PI Connector for BACnet is configured to collect data, it performs the following operations:

• Network communication

• Network inventory

• Asset creation

• Data collection

Network communication

PI Connector for BACnet uses UDP to perform all request and response communication with BACnet devices on the network.

Network inventory

The connector first performs a network inventory by sending Who-Is messages. When I-Am responses are received from devices, subsequent ReadProperty and/or ReadPropertyMultiple requests are sent to each device discovering all objects and properties.

If a device does not respond to Who-Is messages, you can manually specify the complete device configuration. By specifying the device configuration manually, you configure the communication, inventory, and data collection information about devices that do not respond to Who-Is messages.

By default, new Who-Is messages are sent out every 24 hours to discover any new devices on the network or to see if existing devices have changed. Rediscovery can be disabled by changing the RediscoveryFrequency setting to 0 in the data source configuration.

Asset creation

From the results of the inventory, the connector creates PI AF elements and attributes. BACnet devices and objects are represented as PI AF elements, and properties are represented as PI AFattributes.

Data collection

By default, data is collected at a poll interval of 60 seconds for the Present_Value and Status_Flags properties. Optionally, if a data selection file is used (see Selection of devices or objects) the connector can be configured to poll BACnet objects at different scan intervals or subscribe to Change Of Value (COV) services supported by the device.