BACnetStack_SetIntrinsicFloatingLimitAlgorithm

bool BACnetStack_SetIntrinsicFloatingLimitAlgorithm(
  const uint32_t deviceInstance,
  const uint16_t objectType,
  const uint32_t objectInstance,
  const float setpoint,
  const float lowDiffLimit,
  const float highDiffLimit,
  const float deadband,
  const bool enableLowLimit,
  const bool enableHighLimit,
  const uint32_t timeDelay,
  const bool useTimeDelayNormal,
  const uint32_t timeDelayNormal,
  const bool enable);

Enables the Intrinsic Floating Limit Algorithm (135-2024 cl. 13.3.5) for an object.

The object must exist before calling this function. The monitored Present_Value (REAL) is compared against a moving setpoint rather than fixed limits: the normal range is [setpoint - lowDiffLimit, setpoint + highDiffLimit], so the offnormal region tracks setpoint as it changes.

The object must exist and have alarms and events enabled by BACnetStack_SetAlarmsAndEventsForObjectEnabled(…, enabled=true) - an Event Enrollment object carries its own and needs no such call; otherwise this returns false.

lowDiffLimit/highDiffLimit are INDEPENDENT - cl. 13.3.5 defines pLowDiffLimit and pHighDiffLimit as two separate parameters (the amount the monitored value may fall below/rise above the setpoint before LOW_LIMIT/HIGH_LIMIT), so an asymmetric band - the common case in practice, where overshoot and undershoot have different tolerances - can be expressed directly. Pass the same value for both for a symmetric band.

BACnet reference: ANSI/ASHRAE 135-2024 clause 13.3.5 (FLOATING_LIMIT Event Algorithm).

Parameters

Parameter	Direction	Description
`deviceInstance`	in	The instance number of the device that owns this object.
`objectType, objectInstance`	in	The object for alarms and events: one BACnet Object Identifier, carried as two parameters (see the API conventions).
`setpoint`	in	The reference value the monitored Present_Value is compared against.
`lowDiffLimit`	in	The allowed deviation BELOW setpoint before the low limit is exceeded.
`highDiffLimit`	in	The allowed deviation ABOVE setpoint before the high limit is exceeded.
`deadband`	in	The margin by which the value has to come back inside the exceeded limit before the event state returns to normal. A NaN or infinite deadband fails the call and changes nothing.
`enableLowLimit`	in	Ignored: cl. 13.3.5 has no pLimitEnable, so both limits always apply. Kept for the ABI.
`enableHighLimit`	in	Ignored, as enableLowLimit.
`timeDelay`	in	How long, in seconds, an offnormal condition has to persist before the event state changes to offnormal.
`useTimeDelayNormal`	in	Whether to use a different time delay value for the timeDelayNormal, or just use the timeDelay value.
`timeDelayNormal`	in	How long, in seconds, a normal condition has to persist before the event state returns to normal.
`enable`	in	Initial inhibit state, inverted - NOT a remove. true arms the algorithm; false leaves it armed but INHIBITED through the object’s Event_Algorithm_Inhibit property (or Reliability_Evaluation_Inhibit for a fault algorithm). Both of those properties are made WRITABLE by BACnetStack_SetAlarmsAndEventsForObjectEnabled(), so a remote client can change the state afterwards. To genuinely remove an armed algorithm, disable the object with BACnetStack_SetAlarmsAndEventsForObjectEnabled(…, enabled=false). Recommended value: true

Returns

True on success; false if the device or object does not exist, the object type does not support this algorithm, or Alarm-and-Event support was not compiled (STACK_OPTION_ALARMS_AND_EVENTS).

Topic: Alarms and events. Declared in CASBACnetStackDLL.h.