BACnet.Protocol.EventAlgorithms.CommandFailure (bacstack v0.0.1)

View Source

Implements the BACnet event algorithm CommandFailure.

The CommandFailure event algorithm detects whether the monitored value and the feedback value disagree for a time period. It may be used, for example, to verify that a process change has occurred after writing a property.

For more specific information about the event algorithm, consult ASHRAE 135 13.3.4.

Summary

Types

t()

Representative type for the event algorithm.

Functions

execute(state)

Calculates the new state for the current state and parameters. Prior to this function invocation, the state should have been updated with update/2, if any of the properties has changed.

new(monitored_value, params)

Creates a new algorithm state.

update(state, params)

Updates the state using the given parameters (monitored_value, parameters, status_flags).

Types

t()

@opaque t()

Representative type for the event algorithm.

Functions

execute(state)

@spec execute(t()) ::
  {:event, new_state :: t(),
   BACnet.Protocol.NotificationParameters.CommandFailure.t()}
  | {:delayed_event | :no_event, new_state :: t()}

Calculates the new state for the current state and parameters. Prior to this function invocation, the state should have been updated with update/2, if any of the properties has changed.

:delayed_event helps identifying whether the algorithm needs to be called periodically in order to overcome the time_delay and trigger a state change. As soon as :event or :no_event is given as flag, it means the caller can go back to event orientated calling.

The status_flags field of the notifications parameters is updated from the state with the correct in_alarm state, however to ensure the Status Flags have an overall correct status, the user has to make sure all bits are correctly.

ASHRAE 135:

The conditions evaluated by this event algorithm are:

(a) If pCurrentState is NORMAL, and pFeedbackValue is not equal to pMonitoredValue for pTimeDelay, then indicate a transition to the OFFNORMAL event state.

(b) If pCurrentState is OFFNORMAL, and pMonitoredValue is equal to pMonitoredValue for pTimeDelayNormal, then indicate a transition to the NORMAL event state.

new(monitored_value, params)

@spec new(
  BACnet.Protocol.ApplicationTags.Encoding.t(),
  BACnet.Protocol.EventParameters.CommandFailure.t()
) :: t()

Creates a new algorithm state.

The encoding field of Encoding structs is ignored.

update(state, params)

@spec update(t(), Keyword.t()) :: t()

Updates the state using the given parameters (monitored_value, parameters, status_flags).