Data Acquisition Toolbox

How Many Triggers Occurred?

For analog output objects, only one trigger can occur. You can determine if the trigger event occurred by returning the value of the TriggersExecuted property. If TriggersExecuted is 0, then the trigger event did not occur. If TriggersExecuted is 1, then the trigger event occurred. Event information is also recorded by the EventLog property. A convenient way to access event log information is with the showdaqevents function.

For example, suppose you create the analog output object ao for a sound card and add one channel to it. ao is configured to output 8,000 samples using the default sampling rate of 8000 Hz.

• ao = analogoutput('winsound');
  addchannel(ao,1);
  data = sin(linspace(0,1,8000))';
  putdata(ao,data)
  start(ao)
  

TriggersExecuted returns the number of triggers executed.

• ao.TriggersExecuted
  ans =
        1
  

You can use showdaqevents to return information for all events that occurred while ao was executing.

• showdaqevents(ao)
     1 Start               ( 10:43:25, 0 )
     2 Trigger             ( 10:43:25, 0 )
     3 Stop                ( 10:43:26, 8000 )
  

For more information about recording and retrieving event information, refer to Recording and Retrieving Event Information.

Executing the Trigger

When Did the Trigger Occur?