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Events.md

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Events

The framework provides a composition-based event system built on top of TcEventLogger. Events are decoupled from the components that raise them, and the three-interface design (I_EventClass, I_EventArguments, I_EventReaction) keeps components independent of any specific event infrastructure.

I_EventClass

The primary interface for raising, clearing, and binding events.

Member Type Description
RaiseEvent(EventId) Method Raise a specific event by ID
ClearEventById(EventId) Method Clear a specific event by ID
Arguments(EventId) Method → I_EventArguments Access the argument builder for an event
SetEvent(EventId, Trigger, AutoReset) Method Bind a POINTER TO BOOL to an event; raises automatically when TRUE, optionally clears when FALSE
ResetBySeverity(Severity) Method Clear all events at or below the given severity
IsResettable BOOL (Get) TRUE when at least one trigger-bound event is raised but its trigger is currently FALSE

I_EventArguments

Adds context strings to an event before raising it. Supports method chaining.

Member Type Description
AddString(Value) Method → I_EventArguments Append a string argument to the event
Clear() Method Remove all arguments from the event

I_EventReaction

Maps event severities to machine reactions (e.g., stop, abort).

Member Type Description
SetEventReactions(...) Method Assign a reaction for each severity level
GetHighestActiveEventReaction() Method → reaction Returns the most severe active reaction

TcEventClass

Concrete implementation of I_EventClass that integrates with TcEventLogger.

Setup

Step 1 — Create a TcEventClass in the TwinCAT type system.

Add all desired events for the component to this class. Placeholders {0}..{x} in event text are filled by I_EventArguments.

TcEventClass editor

Step 2 — Instantiate and generate events during module initialization.

VAR
    ModuleEvents : TcEventClass;
END_VAR

IF NOT Module.Initialized THEN
    ModuleEvents.GenerateTcEvents(Module.Name, ADR(TC_Events.TestComponent), SIZEOF(ST_TestComponent));
END_IF

Usage

Manual raise and clear:

ModuleEvents.RaiseEvent(E_TestComponent.CriticalEvent);
ModuleEvents.Reset();

Trigger-bound with auto-reset (recommended):

// In FB_Init or initialization sequence — bind a BOOL to an event.
// The event raises automatically when TRUE and clears when it returns to FALSE.
ModuleEvents.SetEvent(E_TestComponent.CriticalEvent, ADR(bFaultCondition), AutoReset := TRUE);

Reset button pattern using IsResettable:

IF ModuleEvents.IsResettable THEN
    // One or more trigger-bound events are raised but trigger is FALSE — safe to reset.
    ModuleEvents.Reset();
END_IF

Adding arguments to an event:

ModuleEvents.Arguments(E_TestComponent.Warning).AddString('Axis 1').AddString('Torque limit');
ModuleEvents.RaiseEvent(E_TestComponent.Warning);

Trace

Global utility for debug logging and diagnostics. Messages are broadcast to TcEventLogger and AdsLogger (both rate-limited to MaxTraceMessagesPerScan). Additional transports can be registered as subscribers.

Trace.LogMessage(Key := 'SourceName', Value := 'Message text');

Key is the source label; Value is the message body. Output format: Value: Key.

Custom logger (file logging, MQTT, or other transports):

Trace.Subscribe(myCustomLogger); // myCustomLogger implements I_TraceLogger