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Chapter 1

Using the NI-DAQ Functions

NI-DAQ FRM for PC Compatibles

1-4

©

 National Instruments Corporation

The previous example describes a parameter that can accept an array of 
signed integers or an array of floating-point numbers.

Apart from the data type differences, there are a few language-dependent 
considerations you need to be aware of when you use the NI-DAQ API. 
Read the following sections that apply to your programming language.

When you pass arrays to NI-DAQ functions using Borland Delphi in 
Windows, you need to pass a pointer to the array. You can either declare an 
array and pass the array address to the NI-DAQ function, or you can 
declare a pointer, dynamically allocate memory for the pointer, and pass 
the pointer directly to the NI-DAQ function. For example,

var

buffer : array [1..1000] of Integer;

bufPtr : ^Integer;

status := DAQ_Start (device, chan, gain, @buffer, count, 

timebase, sampInterval);

or

(* allocate memory for bufPtr first using AllocMem or 

New *)

status := DAQ_Start (device, chan, gain, bufPtr, count, 

timebase, sampInterval);

When you pass arrays to NI-DAQ functions using Visual Basic for 
Windows, you need to pass the first element of the array by reference. For 
example, you would call the 

DAQ_Start

 function using the following 

syntax:

status% = DAQ_Start (device%, chan%, gain%, buffer%(0), 

count&, timebase%, sampInterval%)