Events and Callbacks

Execute functions triggered by specific events

You can enhance the power and flexibility of your OPC application by using event callbacks. An event is a specific occurrence that can happen while an OPC Data Access client object is connected to an OPC server. The toolbox defines a set of events that include starting, stopping, or acquiring records during a logging task, as well as events for asynchronous reads and writes, data changes, and server shutdown notification.

Functions

`opccallback`	Event information for OPC callbacks
`cleareventlog`	Clear event log, discarding all events
`showopcevents`	Event log summary for OPC events

Properties

`ErrorFcn`	Callback function file to execute when error event occurs
`EventLog`	Event information log
`EventLogMax`	Maximum number of events to store in event log
`ShutDownFcn`	Callback function file to execute when OPC server shuts down
`TimerFcn`	Callback function file to execute when predefined period passes
`TimerPeriod`	Period between timer events
`CancelAsyncFcn`	Callback function file to execute when asynchronous operation is canceled
`DataChangeFcn`	Callback function file to execute when data change event occurs
`ReadAsyncFcn`	Callback function file to execute when asynchronous read completes
`RecordsAcquiredFcn`	Callback function file to execute when `RecordsAcquired` event occurs
`RecordsAcquiredFcnCount`	Number of records to acquire before `RecordsAcquired` event occurs
`StartFcn`	Callback function file to execute immediately before logging starts
`StopFcn`	Callback function file to execute immediately after logging stops
`WriteAsyncFcn`	Callback function file to execute when asynchronous write completes

Topics

Use the Default Callback Function
Learn the basics of events and callbacks.
Retrieve Event Information
Access the information generated with each event.
Create and Execute Callback Functions
Write a callback function and associate it with an event callback.
Event Types
Learn all the event types supported by the toolbox.

Featured Examples

View the OPC Event Log

Examine the OPC event log after a logging task.

Open Script

Monitor Logging Progress with Callbacks

Use callbacks to monitor an OPC Data Access logging task.

Open Script

Update MATLAB Plots While Logging OPC Data

Use a custom callback to plot data acquired during an OPC logging task.

Open Script