Technical data

616 Agilent N8201A Performance Downconverter Synthetic Instrument Module, 250 kHz to 26.5 GHz
28 Programming Fundamentals
Programming in C Using the VTL
The programming examples that are provided are written using the C programming
language and the Agilent VTL (VISA transition library). This section includes some basic
information about programming in the C language. Note that some of this information may
not be relevant to your particular application. (For example, if you are not using VXI
instruments, the VXI references will not be relevant).
Refer to your C programming language documentation for more details. (This information is
taken from the manual “VISA Transition Library”, part number E2090-90026.) The following
topics are included:
• “Typical Example Program Contents" on page 616.
• “Linking to VTL Libraries" on page 617.
• “Compiling and Linking a VTL Program" on page 617.
• “Example Program" on page 618.
• “Including the VISA Declarations File" on page 619.
• “Opening a Session" on page 619.
• “Device Sessions" on page 620.
• “Addressing a Session" on page 621.
• “Closing a Session" on page 622.
Typical Example Program Contents
The following is a summary of the VTL function calls used in the example programs.
visa.h This file is included at the beginning of the file to provide the function prototypes
and constants defined by VTL.
ViSession The ViSession is a VTL data type. Each object that will establish a
communication channel must be defined as ViSession.
viOpenDefaultRM You must first open a session with the default resource manager with
the viOpenDefaultRM function. This function will initialize the default resource
manager and return a pointer to that resource manager session.
viOpen This function establishes a communication channel with the device specified. A
session identifier that can be used with other VTL functions is returned. This call must be
made for each device you will be using.
viPrintf viScanf These are the VTL formatted I/O functions that are patterned after
those used in the C programming language. The viPrintf call sends the IEEE 488.2
*RST command to the instrument and puts it in a known state. The viPrintf call is
used again to query for the device identification (*IDN?). The viScanf call is then used
to read the results.