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Chapter 3 Software Overview

NI-DAQ User Manual for PC Compatibles 3-44 ni.com

Basic Waveform Generation with Pauses

The application skeleton described in this section is nearly identical to

the basic waveform generation application skeleton. The difference is that

the description in this section includes the pause and resume operations.

Figure 3-16 illustrates the ordinary series of calls for a basic waveform

application with pauses.

The first step of Figure 3-16 calls

WFM_Group_Setup

.The

WFM_Group_Setup

function assigns one or more analog output channels

to a group.

The second step is to assign a buffer to the analog output channels using the

calls

WFM_Scale

and

WFM_Load

.The

WFM_Scale

function converts

floating-point voltages to integer values that produce the voltages you want.

The

WFM_Load

function assigns a waveform buffer to one or more analog

output channels.

The next step is to assign an update rate to the group of channels using the

calls

WFM_Rate

and

WFM_ClockRate

.The

WFM_Rate

function converts a

data output rate to a timebase and an update interval that generates the rate

you want. The

WFM_ClockRate

function assigns a timebase, update

interval, and delay interval to a group of analog output channels.

Notice that there are restrictions for using the

WFM_ClockRate

function to

specify delay rate. Refer to the

WFM_ClockRate

function description in the

NI-DAQ Function Reference Online Help file for further details.

Your application is now ready to start a waveform generation. Call

WFM_Group_Control

(operation=

START

) to start the waveform

generation in the background.

WFM_Group_Control

will return to your

application after the waveform generation begins.

The next step in Figure 3-16 is an application decision to pause the

waveform generation. The application uses a number of conditions for

making this decision, including status information returned by

WFM_Check

Pause the waveform generation by calling

WFM_Group_Control

(operation=

PAUSE

stops the waveform generation and maintains

the current waveform voltage at the channel output.