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Chapter 3 101
Programming Examples
C Programming Examples using VTL
The session returned from viOpenDefaultRM must be used in the sesn parameter
of the viOpen function. The viOpen function then uses that session and the
device address specified in the (resource name) parameter to open a device
session. The vi parameter in viOpen returns a session identifier that can be used
with other VTL functions.
Your program may have several sessions open at the same time by creating
multiple session identifiers by calling the viOpen function multiple times.
The following summarizes the parameters in the previous function calls:
sesn This is a session returned from the viOpenDefaultRM
function that identifies the resource manager session.
rsrcName This is a unique symbolic name of the device (device address).
accessMode This parameter is not used for VTL. Use VI_NULL.
timeout This parameter is not used for VTL. Use VI_NULL.
vi This is a pointer to the session identifier for this particular
device session. This pointer will be used to identify this device
session when using other VTL functions.
The following is an example of opening sessions with a GPIB multimeter and a
GPIB/VXI scanner:
ViSession defaultRM, dmm, scanner;
.
.
viOpenDefaultRM(&defaultRM);
viOpen(defaultRM, “GPIB0::22::INSTR”, VI_NULL,
VI_NULL, &dmm);
viOpen(defaultRM, “GPIB-VXI0::24::INSTR”, VI_NULL,
VI_NULL, &scanner);
.
.
viClose(scanner);
viClose(dmm);
viClose(defaultRM);