National Instruments NI-VXI

Chapter 2 Introduction to the NI-VXI Functions

9 NI-VXI User Manual

Using NI-VXI

This section presents a general overview of the more commonly used

class of functions available in NI-VXI. Additional information

summarizes how you can use the functions to perform certain tasks and

further describes the general structure of NI-VXI programming.

Header Files

Although nivxi.h is the only header file you need to include in your

program for NI-VXI, the software distribution actually includes several

additional header files along with nivxi.h. Some of these files have

type definitions and macros that can make using NI-VXI easier, and

make the code more portable across different platforms. The three main

files of interest are datasize.h, busacc.h, and devinfo.h.

The datasize.h File

The datasize.h file defines the integer types for use in your

program. For example, INT16 is defined as a 16-bit signed integer, and

UINT32 is defined as a 32-bit unsigned integer. Using these types

benefits you by letting you apply specific type sizes across platforms.

Using undefined types can cause problems when porting your

application between platforms. For example, an int in DOS is a 16-bit

number but a 32-bit number in Solaris or LabWindows/CVI.

In addition to the integers, datasize.h defines several types for other

uses such as interrupt handlers. For example, NIVXI_HVXIINT is an

interrupt handler type. Merely defining a variable with this type is

sufficient to create the function prototype necessary for your interrupt

handler. Also, different platforms require different flags for use with

interrupt handlers. To simplify this problem, datasize.h defines

NIVXI_HQUAL and NIVXI_HSPEC, which are used in the handler

definition and take care of the platform dependencies. See the

Interrupts and Signals section later in this chapter and your read me

file for more information. In addition, refer to Chapter 3, Software

Overview for specific information.