Pi bacnet Interface

Object Reports

BACnet Object reports can be generated by right clicking on a BACnet Device, BACnet Object Type or BACnet Object in the Object Explorer and then selecting View Report. This will cause a window to pop up with the report output in a textbox.

You may save the report to a text file by clicking the Save To File button. If the object list is too long for the textbox, it will prompt to save the report to file directly instead of writing it to the textbox.

The following properties will be included with each BACnet Object (except for Object Type DEVICE) in the report.

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  Instance Number
  
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  OBJECT_NAME
  
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  DESCRIPTION
  
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  OBJECT_IDENTIFIER
  
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  OBJECT_TYPE
  
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  PRESENT_VALUE
  
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  MIN_PRESENT_VALUE (if applicable)
  
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  MAX_PRESENT_VALUE (if applicable)
  
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  COV_INCREMENT (if applicable)
  
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  UNITS (if applicable)
  

The following properties will be included with the BACnet Device when the DEVICE Object is chosen for a report.

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  Instance Number
  
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  OBJECT_IDENTIFIER
  
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  OBJECT_NAME
  
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  OBJECT_TYPE
  
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  SYSTEM_STATUS
  
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  VENDOR_IDENTIFIER
  
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  VENDOR_NAME
  
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  MODEL_NAME
  
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  FIRMWARE_REVISION
  
• 
  APPLICATION_SOFTWARE_VERSION
  
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  DESCRIPTION
  
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  PROTOCOL_VERSION
  
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  PROTOCOL_REVISION
  
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  PROTOCOL_SERVICES_SUPPORTED
  
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  PROTOCOL_OBJECT_TYPES_SUPPORTED
  
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  MAX_APDU_LENGTH_ACCEPTED
  
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  SEGMENTATION_SUPPORTED
  
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  APDU_TIMEOUT
  
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  NUMBER_OF_APDU_RETRIES
  
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  DATABASE_REVISION
  
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  LOCAL_DATE
  
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  LOCAL_TIME
  

COV Subscription Tests

For BACnet Devices that support COV (Change of Value) Subscriptions, you may perform a COV Test by right clicking on a BACnet Property in either the Object Explorer or Query View and then selecting COV Test. This will cause a window to pop up where the COV Test can be requested.

In the Property Info section, the selected BACnet Device ID, BACnet Object Type, BACnet Object ID and BACnet Property will be displayed.

There are two parameters that can be adjusted before initializing the subscription.

• 
  COV Lifetime – Specify the COV Lifetime in seconds. The COV lifetime is the amount of time before a COV subscription expires. For COV testing, the COV lifetime is limited to a range between 1 and 600 seconds.
  
• 
  COV Increment – Specify the amount a value must change before a COV Update Notification is generated by the BACnet Device. A value of zero indicates all changes should generate updates. The COV Increment is not used for non numeric BACnet Properties.
  

If the COV Subscription is successfully initialized, updates will be automatically displayed in the Subscription Data section.

Query Settings

Because the UDP protocol is used for synchronous communication, there are several timing and performance options that can be configured to help communicate properly with the BACnet devices. These settings can be saved to the registry so that they persist between Query sessions. However, the sessions can be tweaked within each session without saving to the registry to allow for testing with committing the settings.

To get to the BACnet Advanced Settings screen, click on the BACnet menu on the menu bar. Then choose the Query Settings menu item.

To save the values to the registry, be sure to check the Save Values to Registry? checkbox. Click the Submit button to save the values.

The Query Settings screen has 2 major sections:

Alternative Query Settings

These settings apply to alternative BACnet communications which are used to query BACnet Device that does not support Segmenation or Read Multiple Property requests. The alternative methods of communications are slower and may require adjustments to achieve the desired performance and reliablity with the queries.

Simultaneous Query Settings

Because of the delays involved, performing the UDP operations would take considerable time, especially when retrieving a large number of objects and/or properties. These settings will determine how many simultaneous requests will be sent to the BACnet Device for each of the query types. The higher the number of simultaneous requests will increase speed but also puts more of load on the BACnet Device and can possibly cause delayed and/or missed responses. The recommended range is between 5 and 25, with a default of 10.

Delay Between Burst Reads

These settings specify how long to wait (to reduce load on the BACnet device) between each set of simultaneous reads. The delays are specified in milliseconds. The recommended range is between 100 and 500 ms, with a default of 100 ms.

Query Retries

If the UDP communications fail, these settings specify how many times to retry acquiring the Device Property, Object Listing or Object Property. The recommended range is between 1 and 5, with a default of 5.

General Settings

These settings apply to general BACnet communications.

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  BACnet Port Number – Specify the port # used for BACnet communications. The default is 47808.
  
• 
  Device Query Delay – Specify how long to wait between requests sent to a BACnet Device. This helps reduce device load. This delay is specified in milliseconds. The recommended range is between 1 and 5 ms, with a default of 2 ms.
  

Response Read Delays

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  These delays are all specified in milliseconds.
  
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  Who IS Broadcast - Specifies how long to wait before attempting to read the messages received from the WhoIS Broadcast. The recommended range is between 500 and 2500 ms, with a default of 1000 ms.
  
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  Object List Query - Specifies how long to wait before attempting to read the message received from the EPICS Unicast. The recommended range is between 250 and 1000 ms, with a default of 500 ms.
  
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  Object Property Query - Specifies how long to wait before attempting to read the message received from the Read Property Unicast. The recommended range is between 250 and 1000 ms, with a default of 250 ms.