Device

The Device object describes the BACnet device itself: who made it, what it supports and which objects it holds. Every device has exactly one. Clients read it first to learn what they are talking to, then read its Object_List to find the rest.

Typical uses

• Identify the vendor and model
• List every object the product exposes
• Check which services the device supports
• Detect that the configuration changed
• Read the device’s local date and time

Key properties

Property	What it holds
Object_List	Every object in the device. Clients read it to discover the device’s points.
Vendor_Identifier	The number ASHRAE assigned to the manufacturer.
Protocol_Services_Supported	Which BACnet services the device accepts.
Protocol_Object_Types_Supported	Which object types the device can hold.
Database_Revision	Changes whenever the object list or object names change. Clients use it to know when to re-read.
System_Status	Whether the device is operational, in a backup or restore, or otherwise limited.

How it behaves

The standard defines no event algorithm for a Device. Clients cannot create or delete a Device object.

With the CAS BACnet Stack

Call BACnetStack_AddDevice once, before any other setup call. A second call is rejected. Add further logical devices with BACnetStack_AddDeviceToVirtualNetwork. The stack keeps Object_Identifier, Object_Type, Object_List, System_Status and Device_Address_Binding, and updates Database_Revision as objects are added. It also holds the segmentation properties, which you set with BACnetStack_SetSegmentationEnabled. Your callbacks serve the rest: Vendor_Name and Model_Name through the callback you register with BACnetStack_RegisterCallbackGetPropertyCharacterString, and Vendor_Identifier through the BACnetStack_RegisterCallbackGetPropertyUnsignedInteger callback. Until they answer, the stack serves the defaults in the table below, which name Chipkin, so serve your own. APDU_Timeout and Number_Of_APDU_Retries default to 10000 ms and 3 unless you serve them. The standard applies no event algorithm to a Device and the stack serves no event state for it, so there is nothing to arm: BACnetStack_SetAlarmsAndEventsForObjectEnabled accepts the object but changes nothing a client can see.

Related object types

Network Port, File, Notification Class, Calendar

Properties

The properties ASHRAE 135-2024 clause 12.11 defines for this object type.

How to read the table:

• Conformance is what the standard asks of every object of this type: R is required, W is required and writable by a client, O is optional. A digit after the letter marks a condition in the standard that decides when the property is present or writable, such as support for intrinsic reporting.
• Present by default: yes means the stack presents the property as soon as you add the object; no means it is optional and you turn it on with BACnetStack_SetPropertyEnabled. This is the stack’s starting setup, so it can differ from the conformance code.
• Writable is whether a client can write the property by default. Change it with BACnetStack_SetPropertyWritable.
• not in profile means the stack does not offer this property for this object type.
• Value when your callback does not answer: “Held by the stack” means the stack stores and serves the value itself and does not ask your callbacks. Otherwise it is the value the stack answers when your callback declines or is not registered.

Property	Datatype	Conformance	Present by default	Writable	Value when your callback does not answer
Object_Identifier	BACnetObjectIdentifier	R	yes	no	Held by the stack.
Object_Name	CharacterString	R	yes	no	"Chipkin BACnet Device"
Object_Type	BACnetObjectType	R	yes	no	Held by the stack.
System_Status	BACnetDeviceStatus	R	yes	no	Held by the stack.
Vendor_Name	CharacterString	R	yes	no	"Chipkin Automation Systems"
Vendor_Identifier	Unsigned16	R	yes	no	389
Model_Name	CharacterString	R	yes	no	"CAS BACnet Stack"
Firmware_Revision	CharacterString	R	yes	no	The stack version as four numbers, such as "6.0.0.0".
Application_Software_Version	CharacterString	R	yes	no	"v1"
Location	CharacterString	O	no	no	""
Description	CharacterString	O	no	no	""
Protocol_Version	Unsigned	R	yes	no	1
Protocol_Revision	Unsigned	R	yes	no	30, the stack’s protocol revision.
Protocol_Services_Supported	BACnetServicesSupported	R	yes	no	Computed from the services that are enabled.
Protocol_Object_Types_Supported	BACnetObjectTypesSupported	R	yes	no	Computed from the object types that are supported.
Object_List	BACnetARRAY[N] of BACnetObjectIdentifier	R	yes	no	Held by the stack.
Structured_Object_List	BACnetARRAY[N] of BACnetObjectIdentifier	O	no	no	No default: the read fails.
Max_APDU_Length_Accepted	Unsigned	R	yes	no	1476
Segmentation_Supported	BACnetSegmentation	R	yes	no	Held by the stack: 0 (segmented-both) in a build with segmentation, otherwise 3 (no segmentation). Change it with BACnetStack_SetSegmentationEnabled.
Max_Segments_Accepted	Unsigned	O1	yes in a build with segmentation, which a default device supports (Table 12-13 footnote 1); no when the device is set to no segmentation	no	Held by the stack: 16 in a build with segmentation, otherwise not served. Change it with BACnetStack_SetSegmentationEnabled.
VT_Classes_Supported	BACnetLIST of BACnetVTClass	O2	no	no	0
Active_VT_Sessions	BACnetLIST of BACnetVTSession	O2	no	no	No default: the read fails.
Local_Time	Time	O3,4,12	no	no	No default: value-not-initialized until a callback or a client write supplies one.
Local_Date	Date	O3,4,12	no	no	No default: value-not-initialized until a callback or a client write supplies one.
UTC_Offset	Integer	O4	no	no	0
Daylight_Savings_Status	Boolean	O4	no	no	false
APDU_Segment_Timeout	Unsigned	O1	yes in a build with segmentation, which a default device supports (Table 12-13 footnote 1); no when the device is set to no segmentation	no	Held by the stack: 5000 (ms) in a build with segmentation, otherwise not served. Change it with BACnetStack_SetSegmentationEnabled.
APDU_Timeout	Unsigned	R	yes	no	10000 (ms)
Number_Of_APDU_Retries	Unsigned	R	yes	no	3: a confirmed request is sent up to four times. Serve 0 to send it once.
Time_Synchronization_Recipients	BACnetLIST of BACnetRecipient	O5	no	yes	Held by the stack.
Max_Manager	Unsigned(0..127)	O6	no	no	0
Max_Info_Frames	Unsigned	O6	no	no	0
Device_Address_Binding	BACnetLIST of BACnetAddressBinding	R	yes	no	Held by the stack.
Database_Revision	Unsigned	R	yes	no	Held by the stack; a Get callback that answers wins.
Configuration_Files	BACnetARRAY[N] of BACnetObjectIdentifier	O7	no	no	Held by the stack.
Last_Restore_Time	BACnetTimeStamp	O7	no	no	Held by the stack.
Backup_Failure_Timeout	Unsigned16	O8	no	yes	Held by the stack.
Backup_Preparation_Time	Unsigned16	O13	no	no	Held by the stack.
Restore_Preparation_Time	Unsigned16	O13	no	no	Held by the stack.
Restore_Completion_Time	Unsigned16	O13	no	no	Held by the stack.
Backup_And_Restore_State	BACnetBackupState	O7	no	no	Held by the stack.
Active_COV_Subscriptions	BACnetLIST of BACnetCOVSubscription	O9	no	no	Held by the stack.
Last_Restart_Reason	BACnetRestartReason	O10	no	no	0
Time_Of_Device_Restart	BACnetTimeStamp	O10	no	no	No default: the read fails.
Restart_Notification_Recipients	BACnetLIST of BACnetRecipient	O14	no	no	No default: the read fails.
UTC_Time_Synchronization_Recipients	BACnetLIST of BACnetRecipient	O5	no	yes	Held by the stack.
Time_Synchronization_Interval	Unsigned	O5	no	yes	0
Align_Intervals	Boolean	O5	no	yes	false
Interval_Offset	Unsigned	O5	no	yes	0
Serial_Number	CharacterString	O11	no	no	""
Property_List	BACnetARRAY[N] of BACnetPropertyIdentifier	R	yes	no	Held by the stack.
Status_Flags	BACnetStatusFlags	O15	no	no	Built by the stack from your callbacks.
Event_State	BACnetEventState	O15	no	no	0
Reliability	BACnetReliability	O15	no	no	0
Event_Detection_Enable	Boolean	O15,16	no	no	false
Notification_Class	Unsigned	O15,16	no	no	0
Event_Enable	BACnetEventTransitionBits	O15,16	no	no	An empty bit string.
Acked_Transitions	BACnetEventTransitionBits	O15,16	no	no	An empty bit string.
Notify_Type	BACnetNotifyType	O15,16	no	no	0
Event_Time_Stamps	BACnetARRAY[3] of BACnetTimeStamp	O15,16	no	no	No default: the read fails.
Event_Message_Texts	BACnetARRAY[3] of CharacterString	O16	no	no	""
Event_Message_Texts_Config	BACnetARRAY[3] of CharacterString	O16	no	no	""
Reliability_Evaluation_Inhibit	Boolean	O17	no	no	false
Active_COV_Multiple_Subscriptions	BACnetLIST of BACnetCOVMultipleSubscription	O18	no	no	Held by the stack.
Audit_Notification_Recipient	BACnetRecipient	O19,20	no	yes	No default: the read fails.
Audit_Level	BACnetAuditLevel	O21	not in profile	not in profile	No default: the read fails.
Auditable_Operations	BACnetAuditOperationFlags	O21	not in profile	not in profile	No default: the read fails.
Device_UUID	OctetString (Size(16))	O22	no	no	An empty octet string.
Authorization_Server	BACnetAuthorizationServer	O23	no	no	No default: the read fails.
Authorization_Status	BACnetAuthorizationStatus	O23	no	no	No default: the read fails.
Authorization_Policy	BACnetARRAY of BACnetAuthorizationPolicy	O	no	no	No default: the read fails.
Authorization_Scope	BACnetARRAY of BACnetAuthorizationScopeDescription	O	no	no	No default: the read fails.
Authorization_Cache	BACnetLIST of BACnetAccessToken	O24	no	no	No default: the read fails.
Authorization_Groups	BACnetARRAY of Unsigned	O	no	no	0
Max_Proxied_I_Ams_Per_Second	Unsigned	O25	no	yes	0
Device_Address_Proxy_Table	BACnetLIST of BACnetDeviceAddressProxyTableEntry	O26	no	no	No default: the read fails.
Tags	BACnetARRAY[N] of BACnetNameValue	O	no	no	No default: the read fails.
Profile_Location	CharacterString	O	no	no	""
Deployed_Profile_Location	CharacterString	O19	no	yes	""
Profile_Name	CharacterString	O	no	no	""