National Instruments Image Acquisition Software - Manual (Page 23)

Chapter 3 Programming with NI-IMAQ
© National Instruments Corporation 3-3 NI-IMAQ User Manual
Before you can acquire image data successfully, you must open an interface
by using the
imgInterfaceOpen function. imgInterfaceOpen requires
an interface name and returns a handle to this interface. NI-IMAQ then uses
this handle to reference this interface when using other NI-IMAQ
functions.
To establish a connection to the first board in your system, use the
following program example:
INTERFACE_ID interfaceID;
if (imgInterfaceOpen(“img0”, &interfaceID) == IMG_ERR_GOOD)
{
… user code …
imgClose(interfaceID, FALSE);
}
This example opens an interface to img0 . When the program is finished
with the interface, it closes the interface using the imgClose function.
For a complete list of the available interface functions, refer to the
NI-IMAQ Function Reference Manual.
Session Functions
Use session functions to configure the type of acquisition you want
to perform on a particular interface. After you have established a
connection to an interface, you need to create a session and configure it
to perform the type of acquisition you require.
To create a session, call the imgSessionOpen function. This function
requires a valid interface handle and returns a handle to a session.
NI-IMAQ then uses this session handle to reference this session when using
other NI-IMAQ calls.
To create a session, use the following example program:
INTERFACE_ID interfaceID;
SESSION_ID sessionID;
if (imgInterfaceOpen(“img0”, &interfaceID) == IMG_ERR_GOOD)
{
if (imgSessionOpen(interfaceID, &sessionID) == IMG_ERR_GOOD)
{
… user code …
imgClose(sessionID, FALSE);
}
imgClose(interfaceID, FALSE);
}
UM.book Page 3 Monday, July 13, 1998 9:49 AM