Pi bacnet Interface

PI Point Configuration

The PI point is the basic building block for controlling data flow to and from the PI Server. A single point is configured for each measurement value that needs to be archived.

Point Attributes

Use the point attributes below to define the PI Point configuration for the Interface, including specifically what data to transfer.

Tag

The Tag attribute (or tagname) is the name for a point. There is a one-to-one correspondence between the name of a point and the point itself. Because of this relationship, PI documentation uses the terms “tag” and “point” interchangeably.

Follow these rules for naming PI points:

• 
  The name must be unique on the PI Server.
  
• 
  The first character must be alphanumeric, the underscore (_), or the percent sign (%).
  
• 
  Control characters such as linefeeds or tabs are illegal.
  
• 
  The following characters also are illegal: * ’ ? ; { } [ ] | \ ` ‘ "
  

Length

Depending on the version of the PI API and the PI Server, this Interface supports tags whose length is at most 255 or 1023 characters. The following table indicates the maximum length of this attribute for all the different combinations of PI API and PI Server versions.

PI API	PI Server	Maximum Length
1.6.0.2 or higher	3.4.370.x or higher	1023
1.6.0.2 or higher	Below 3.4.370.x	255
Below 1.6.0.2	3.4.370.x or higher	255
Below 1.6.0.2	Below 3.4.370.x	255

If the PI Server version is earlier than 3.4.370.x or the PI API version is earlier than 1.6.0.2, and you want to use a maximum tag length of 1023, you need to enable the PI SDK. See Appendix B. PI SDK Options for information.

PointSource

The PointSource is a unique, single or multi-character string that is used to identify the PI point as a point that belongs to a particular interface. For additional information, see the /ps command-line parameter and the “PointSource” section.

PointType

Typically, device point types do not need to correspond to PI point types. For example, integer values from a device can be sent to floating point or digital PI tags. Similarly, a floating-point value from the device can be sent to integer or digital PI tags, although the values will be truncated.

Float16, float32, float 64, int16, int32, digital, and string point types are supported. For more information on the individual PointTypes, see PI Server manuals.

Location1

Location1 indicates to which copy of the interface the point belongs. The value of this attribute must match the /id startup parameter.

Location2

Location2 indicates the direction of data flow.

Inputs

Location2 = 0

Defines a tag as an input tag (data goes from BACnet device to PI).

Input points can be scan-based or unsolicited. See the Location4 attribute description for details about how to configure the update method for input tags.

Outputs

Location2 = 1

Defines a tag as an output tag (data goes from PI to BACnet device).

Output point updates are event-triggered. See the section Output Points below for additional configuration information.

Location3

Location3 is not used by this interface.

Location4

Scan-based Inputs

For interfaces that support scan-based collection of data, Location4 defines the scan class for the PI point. The scan class determines the frequency at which input points are scanned for new values. For more information, see the description of the /f parameter in the Startup Command File section.

Unsolicited Inputs and Outputs

Location 4 should be set to zero for these points.

Location5

Location5 is not used by this interface.

InstrumentTag

Length

Depending on the version of the PI API and the PI Server, this Interface supports an InstrumentTag attribute whose length is at most 32 or 1023 characters. The following table indicates the maximum length of this attribute for all the different combinations of PI API and PI Server versions.

PI API	PI Server	Maximum Length
1.6.0.2 or higher	3.4.370.x or higher	1023
1.6.0.2 or higher	Below 3.4.370.x	32
Below 1.6.0.2	3.4.370.x or higher	32
Below 1.6.0.2	Below 3.4.370.x	32

If the PI Server version is earlier than 3.4.370.x or the PI API version is earlier than 1.6.0.2, and you want to use a maximum InstrumentTag length of 1023, you need to enable the PI SDK. See Appendix B for information.

The Instrument Tag contains the communication parameters for BACnet. The following parameters can be used in the InstrumentTag.

• 
  /DeviceIP – IP Address of a BACnet Device
  
• 
  /ObjectID – BACnet Object ID
  
• 
  /ObjectType – BACnet Object Type.
  
• 
  /ObjectProperty – BACnet Object Property
  
• 
  /COV(optional) – Indicating COV processing for an object
  
• 
  /COVIncrement(optional) – Specifying the amount of change that a value must change by before the BACnet controller will send the value to the PI BACnet Interface. The COVIncrement parameter is optional. If the tag is to get values from the BACnet controller using COV and COVIncrement is not specified, then the PI tag attribute excdev will be used as COVIncrement.
  
• 
  /RouterDeviceID(optional) – BACnet Device ID of a BACnet router
  
• 
  /DeviceID(optional) – BACnet Sub-device ID behind a BACnet router
  
• 
  /DeviceMAC(optional) – BACnet Sub-device ID as MAC address behind a BACnet router. It is in the format of xxx-xxx-xxx-xxx-xxx-xxx, where each xxx is the decimal representation of the MAC address byte number.
  
• 
  /LocalIP(optional) – IP Address of the interface node to be used for communication with the BACnet device, if more than one IP address exists. Refer to Principles of Operation for details.
  

Each parameter should be listed with an “=” separating the parameter identifier and the value with no spaces in between, except for /COV which is specified using only the parameter identifier and no value. Each parameter should be separated by a space.

Examples of the InstrumentTag attribute:

/DeviceIP=192.168.4.229 /ObjectID=12 /ObjectType=ANALOG_INPUT /ObjectProperty=PRESENT_VALUE
/DeviceIP=192.168.4.229 /ObjectID=31 /ObjectType=ANALOG_VALUE /ObjectProperty=PRESENT_VALUE /COV /COVIncrement=0.5
/DeviceIP=192.168.4.184 /ObjectID=186 /ObjectType=ANALOG_INPUT /ObjectProperty=PRESENT_VALUE /RouterDeviceID=500 /DeviceID=3

ExDesc

ExDesc is not used for this interface except for Performance Points.

Length

Depending on the version of the PI API and the PI Server, this Interface supports an Extended Descriptor attribute whose length is at most 32 or 1023 characters. The following table indicates the maximum length of this attribute for all the different combinations of PI API and PI Server versions.

PI API	PI Server	Maximum Length
1.6.0.2 or higher	3.4.370.x or higher	1023
1.6.0.2 or higher	Below 3.4.370.x	80
Below 1.6.0.2	3.4.370.x or higher	80
Below 1.6.0.2	Below 3.4.370.x	80

If the PI Server version is earlier than 3.4.370.x or the PI API version is earlier than 1.6.0.2, and you want to use a maximum InstrumentTag length of 1023, you need to enable the PI SDK. See Appendix B. PI SDK Options for information.

Performance Points

For UniInt-based interfaces, the extended descriptor is checked for the string “PERFORMANCE_POINT”. If this character string is found, UniInt treats this point as a performance point. See the section called Performance Counters Points.

Scan

By default, the Scan attribute has a value of 1, which means that scanning is turned on for the point. Setting the scan attribute to 0 turns scanning off. If the scan attribute is 0 when the interface starts, a message is written to the pipc.log and the tag is not loaded by the interface. There is one exception to the previous statement.

If any PI Point is removed from the interface while the interface is running (including setting the scan attribute to 0), SCAN OFF will be written to the PI Point regardless of the value of the Scan attribute. Two examples of actions that would remove a PI Point from an interface are to change the point source or set the scan attribute to 0. If an interface specific attribute is changed that causes the tag to be rejected by the interface, SCAN OFF will be written to the PI point.

Shutdown

The Shutdown attribute is 1 (true) by default. The default behavior of the PI Shutdown subsystem is to write the SHUTDOWN digital state to all PI points when PI is started. The timestamp that is used for the SHUTDOWN events is retrieved from a file that is updated by the Snapshot Subsystem. The timestamp is usually updated every 15 minutes, which means that the timestamp for the SHUTDOWN events will be accurate to within 15 minutes in the event of a power failure. For additional information on shutdown events, refer to PI Server manuals.

Note: The SHUTDOWN events that are written by the PI Shutdown subsystem are independent of the SHUTDOWN events that are written by the interface when the /stopstat=Shutdown command-line parameter is specified.

SHUTDOWN events can be disabled from being written to PI when PI is restarted by setting the Shutdown attribute to 0 for each point. Alternatively, the default behavior of the PI Shutdown Subsystem can be changed to write SHUTDOWN events only for PI points that have their Shutdown attribute set to 0. To change the default behavior, edit the \PI\dat\Shutdown.dat file, as discussed in PI Server manuals.

Bufserv and PIBufSS

It is undesirable to write shutdown events when buffering is being used. Bufserv and PIBufSS are utility programs that provide the capability to store and forward events to a PI Server, allowing continuous data collection when the Server is down for maintenance, upgrades, backups, and unexpected failures. That is, when PI is shutdown, Bufserv or PIBufSS will continue to collect data for the interface, making it undesirable to write SHUTDOWN events to the PI points for this interface. Disabling Shutdown is recommended when sending data to a Highly Available PI Server Collective. Refer to the Bufserv or PIBufSS manuals for additional information.