Analog Output (Data Acquisition Toolbox)

Data Acquisition Toolbox

Recording and Retrieving Event Information

For some of the events listed above, certain information is automatically stored in the EventLog property. EventLog is a structure that contains two fields: Type and Data. The Type field contains the event type. The event types that are logged for analog output objects are start, stop, trigger, runtime error, and out-of-data events. Data-output events and timer events are not stored in EventLog.

The Data field contains the event-specific subfields shown below.

**Table 5-8: EventLog Subfields**
Events	Data Subfield	Description
`All events`	TimeStamp	The absolute time the event occurred.
`All events`	SampleStamp	The number of samples acquired when the event occurred. The sample count begins when the `start` function is issued.
Trigger	Trigger	The trigger number
`Out-of-data`	Channel	The channels(s) that experienced an out-of-data condition

The example below illustrates how you can retrieve event information.

Example: Retrieving Event Information

Suppose you want to examine the events logged for the example on page 5-26. You can do this by accessing the EventLog property.

events = AO.EventLog

By examining the contents of the Type field, you can list the events that were recorded while the data was output.

{events.Type}
ans = 
    'Start'    'Trigger'    'Stop'

Note:
Unless a runtime error occurs, all data acquisition sessions must have a start event, a trigger event, and a stop event.

The Data field of the trigger event recorded the absolute time the trigger occurred, the number of samples output from when the start event occurred and the trigger occurred, and the trigger number.

trigdata = events(2).Data
trigdata = 
      TimeStamp: 7.3001e+005
    SampleStamp: 0
        Trigger: 1

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