Lighting Output

A Lighting Output object controls and reports one dimmable light or lighting load. A client sets a level, ramps, fades or steps it with a lighting command. The object also tracks the level the light has reached. It suits dimmable luminaires and lighting controllers.

Typical uses

• Dim a ceiling light to 40 percent
• Fade a corridor light up over several seconds
• Step brightness up or down from a wall control
• Report the actual level and power draw of a luminaire

Key properties

Property	What it holds
Present_Value	The requested brightness level as a percent. It is commandable.
Lighting_Command	A structured command: set a level, fade, ramp, step, warn or stop. Writing it is the main way to control the light.
Tracking_Value	The level the light has actually reached while a fade or ramp runs.
In_Progress	Shows whether a fade, ramp or step is running.
Default_Fade_Time	The fade time used when a command does not give one.
Default_Ramp_Rate	The ramp rate used when a command does not give one.

How it behaves

A Lighting Output is always commandable, with a priority array of 16 levels. The standard applies no event algorithm to it; where reporting is supported, it only reports faults through Reliability, which then shows in Event_State.

With the CAS BACnet Stack

Enable it with the STACK_OPTION_OBJECT_TYPE_LIGHTING_OUTPUT build option and add each object with BACnetStack_AddObject; it is always commandable. Present_Value is a Real: the stack reads the priority array through the callback you register with BACnetStack_RegisterCallbackGetPropertyBool (is the slot empty) and the BACnetStack_RegisterCallbackGetPropertyReal callback (the slot value), and writes through the BACnetStack_RegisterCallbackSetPropertyReal callback, as the BACnetStack_AddObject page describes. Supply Lighting_Command with BACnetStack_RegisterCallbackGetPropertyLightingCommand and accept writes to it with BACnetStack_RegisterCallbackSetPropertyLightingCommand; a Lighting Output needs both to be conformant. Serve Object_Name with the BACnetStack_RegisterCallbackGetPropertyCharacterString callback. To report faults, enable them with BACnetStack_SetAlarmsAndEventsForObjectEnabled, which attaches the NONE event algorithm; Event_State then shows FAULT while a Reliability fault is held.

Related object types

Binary Lighting Output, Channel, Color, Color Temperature

Properties

The properties ASHRAE 135-2024 clause 12.54 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	"Object <type>,<instance>", such as "Object 0,1" for Analog Input 1.
Object_Type	BACnetObjectType	R	yes	no	Held by the stack.
Present_Value	Real	W	yes	yes	Built by the stack from the priority array your callbacks serve, or Relinquish_Default when every slot is empty.
Tracking_Value	Real	R	yes	no	0.0
Lighting_Command	BACnetLightingCommand	W	yes	yes	No default: the read fails.
In_Progress	BACnetLightingInProgress	R	yes	no	0
Description	CharacterString	O	no	no	""
Status_Flags	BACnetStatusFlags	R	yes	no	Built by the stack from your callbacks.
Event_State	BACnetEventState	O1	no	no	0
Reliability	BACnetReliability	O	no	no	0
Out_Of_Service	Boolean	R	yes	no	false
Blink_Warn_Enable	Boolean	R	yes	no	false
Egress_Time	Unsigned	R	yes	no	0
Egress_Active	Boolean	R	yes	no	false
Default_Fade_Time	Unsigned	R	yes	no	0
Default_Ramp_Rate	Real	R	yes	no	0.0
Default_Step_Increment	Real	R	yes	no	0.0
Transition	BACnetLightingTransition	O	no	no	0
Feedback_Value	Real	O	no	no	0.0
Priority_Array	BACnetARRAY[16] of BACnetOptionalReal	R	yes	no	Built by the stack from your callbacks.
Relinquish_Default	Real	R	yes	no	No default: value-not-initialized until a callback or a client write supplies one.
Power	Real	O	no	no	0.0
Instantaneous_Power	Real	O	no	no	0.0
Min_Actual_Value	Real	O2,15	no	no	0.0
Max_Actual_Value	Real	O2,15	no	no	0.0
Lighting_Command_Default_Priority	Unsigned	R	yes	no	0
COV_Increment	Real	O3	no	no	0.0
Event_Detection_Enable	Boolean	O1,4	no	no	false
Notification_Class	Unsigned	O1,4	no	no	0
Event_Enable	BACnetEventTransitionBits	O1,4	no	no	An empty bit string.
Acked_Transitions	BACnetEventTransitionBits	O1,4	no	no	An empty bit string.
Notify_Type	Boolean	O1,4	no	no	0
Event_Time_Stamps	BACnetARRAY[3] of BACnetTimeStamp	O1,4	no	no	No default: the read fails.
Event_Message_Texts	BACnetARRAY[3] of CharacterString	O4	no	no	""
Event_Message_Texts_Config	BACnetARRAY[3] of CharacterString	O4	no	no	""
Reliability_Evaluation_Inhibit	Boolean	O5	no	no	false
Property_List	BACnetARRAY[N] of BACnetPropertyIdentifier	R	yes	no	Held by the stack.
Current_Command_Priority	BACnetOptionalUnsigned	R	yes	no	Built by the stack from your callbacks.
Value_Source	BACnetValueSource	O6,8,10	no	no	No default: the read fails.
Value_Source_Array	BACnetARRAY[16] of BACnetValueSource	O7,9	no	no	No default: the read fails.
Last_Command_Time	BACnetTimeStamp	O7,9	no	no	No default: the read fails.
Command_Time_Array	BACnetARRAY[16] of BACnetTimeStamp	O9	no	no	No default: the read fails.
Last_On_Value	Real	R	yes	no	0.0
Default_On_Value	Real	R	yes	no	0.0
Audit_Level	BACnetAuditLevel	O11	not in profile	not in profile	No default: the read fails.
Auditable_Operations	BACnetAuditOperationFlags	O11	not in profile	not in profile	No default: the read fails.
Audit_Priority_Filter	BACnetOptionalPriorityFilter	O11	not in profile	not in profile	No default: the read fails.
Color_Reference	BACnetObjectIdentifier	O12	no	no	No default: the read fails.
Color_Override	Boolean	O13	no	yes	false
Override_Color_Reference	BACnetObjectIdentifier	O13	no	no	No default: the read fails.
High_End_Trim	Real	O	no	no	0.0
Low_End_Trim	Real	O	no	no	0.0
Trim_Fade_Time	Unsigned	O14	no	no	0
Tags	BACnetARRAY[N] of BACnetNameValue	O	no	no	No default: the read fails.
Profile_Location	CharacterString	O	no	no	""
Profile_Name	CharacterString	O	no	no	""