Справочник Пользователя для National Instruments Image Acquisition Software

Chapter 3

Programming with NI-IMAQ

3-14

©

 National Instruments Corporation

Figure 3-6.  Signal I/O Function Programming Flowchart

You can use low-level functions or combine high-and low-level functions 
for more advanced programming techniques, including snap, grab, 
sequence, ring, and color image acquisitions.

The 

LLSnap.c 

example demonstrates how to perform a snap acquisition 

using low-level calls. The example sets up a single-frame acquisition to a 
buffer allocated by NI-IMAQ. The program retrieves the acquisition 
window width of the selected camera and aligns it on a 32-bit boundary. 
You must align both the acquisition window width and rowPixels on a 
32-bit boundary to ensure that your image is acquired properly. The 
software does not perform this alignment for you unless you select a scaling 
option. Although the IMAQ Configuration Utility performs this alignment 

imgSessionTriggerDrive

 

configures the session

so that RTSI trigger line 3 will be driven high when the
acquisition has completed.

imgInterfaceOpen

imgInterfaceOpen

 opens and configures the 

interface according to the file set up by the 
IMAQ Configuration Utility

.

imgSessionOpen

 

opens a session that

will be used for an acquisition.

User-specific image processing.

imgClose

 closes the session and interface.

imgSessionOpen

imgSessionTriggerConfigure

 

c

onfigures the 

session so that an acquisition will not occur until a trigger
is received on external trigger line 1.

imgSessionTriggerConfigure

imgSnap

 starts the acquisition. The actual snap will 

not occur until the trigger is received.

imgSnap

imgSessionTriggerDrive

User-Specific Functions

imgClose

UM.book  Page 14  Monday, July 13, 1998  9:49 AM