User manual

Chapter 3 Software Overview
© National Instruments Corporation 3-9 NI-DAQ User Manual for PC Compatibles
4. Start an asynchronous data acquisition or generation operation.
5. When the selected event occurs, the
GeneralDAQEventn_Fire
procedure is called. You can perform the necessary event processing
within this procedure, such as updating a global count variable, or
toggling digital I/O lines.
The
GeneralDAQEventn_Fire
procedure is prototyped as follows:
Sub GeneralDAQEventn_Fire
(DoneFlag As Integer, Scans As Long)
The parameter DoneFlag equals 1 if the acquisition was over when the
DAQ Event fired. Otherwise, it is 0. Scans equals the number of the scan
that caused the DAQ Event to fire.
For a detailed example of how to use the General DAQ Event control in a
Visual Basic program, please see the General DAQ Event example at the
end of the NI-DAQ Events in Visual Basic for Windows section.
Analog Trigger Event
Use the Analog Trigger Event control to configure and enable an analog
trigger.SeetheEvent Message Functions section earlier in this chapter for
a definition of the analog trigger.
Table 3-2 lists the properties for the Analog Trigger Event control.
Table 3-2. Analog Trigger Event Control Properties
Property Allowed Property Values
Name
GeneralDAQEventn (default)
Board
1–n (default)
ChanStr
See
Config_DAQ_Event_Message
in the
NI-DAQ Function Reference Online Help file
Level
Single (voltage)
WindowSize
Single (voltage)
Slope
0—Positive (default)
1—Negative
TrigSkipCount
Long
PreTrigScans
Long
PostTrigScans
Long