error 'DAQmxErrorSamplesWillNeverBeGenerated'

[I_B]

The error 'DAQmxErrorSamplesWillNeverBeGenerated' is generated when attempting to use the DAC on the 6225 to output a signal. A description of how to replicate the problem is provided below. I would appreciate any comments/suggestions that will help correct the problem.

Thanks

Ian





My application is written using Micrsoft Net VC++ compiler under WinXP PRO. The application is designed to output a square wave, 2 or more times, via the DAC. The duration of each square wave is 10ms and the time between them is 1 to 10 seconds.

The code provided below illustrates how the problem can be replicated. The signal is successfully output a first time. However, the error occurs when the function 'DAQmxWriteBinaryI32' is executed the second time. The error code produced is 'DAQmxErrorSamplesWillNeverBeGenerated' and the corresponding text message is:

"Attempted to write a sample beyond the final sample generated.
The generation has stopped, therefore the sample specified by
the combination of position and offset will never be available.
Specify a position and offset which selects a sample up to,
but not beyond, the final sample generated. The final sample
generated can be determined by querying the total samples
generated after a generation".

The following code illustrates how to replicate the problem. Note, this is not the actual code I use but it does illustrate the actual function calls, function arguments and calling function sequence used.

int32 aiData[10] = { 0, 32000, 32000, 32000, 32000, 32000, 32000, 32000, 32000, 0 };
int ictSamples = 10;

TaskHandle hAO; // handle for analog output
VERIFY( DAQmxCreateTask( "AO", &hAO ) == 0 );
VERIFY( DAQmxCreateAOVoltageChan( hAO, "6225a/ao0", "", -10, 10, NULL ) == 0 );

float64 fSamplingRate = 1000.0; // 1000Hz signal
for( int ix = 0; ix < 10; ++ix ) {
VERIFY( DAQmxCfgOutputBuffer( hAO, ictSamples ) == 0 );
VERIFY( DAQmxCfgSampClkTiming( hAO, "", fSamplingRate, DAQmx_Val_Rising,
DAQmx_Val_FiniteSamps, ictSamples ) == 0 );

// error occurs the second time (i.e. ix == 1) that the following function is executed
int32 ictSamplesWritten;
int32 iStatus = DAQmxWriteBinaryI32( hAO, 1000, TRUE, 10.0, DAQmx_Val_GroupByScanNumber,
aiData, &ictSamplesWritten );
VERIFY( 0 == iStatus );
VERIFY( ictSamplesWritten == ictSamples );

// wait before presenting next square wave
::Sleep( 1000 + (rand() % 9000) );

}

... cleanup and shut down code ...

[I_B]

Please note the following correction:
DAQmxWriteBinaryI32( hAO, 100, ...

should be changed to:
DAQmxWriteBinaryI32( hAO, ictSamples, ...

[sergesl]

hello I B,

Two suggestions for you:
1- Do not configure the output buffer. "NI-DAQmx automatically configures the buffer when you configure sample timing" I took this quote directly out of the NI-DAQmx C Reference Help.

2- Start the task and only stop it once you are done.

Hope this helps.

[I_B]

Hello Serge,

1. The documentation states, "If you do not configure the buffer size using DAQmxCfgOutputBuffer, NI-DAQmx automatically configures the buffer when you configure sample timing". So the buffer can be manually allocated using 'DAQmxCfgOutputBuffer'. The error still occurs regardless of whether the buffer is manually/automatically allocated.

2. The task is supposedly automatically started/stopped by passing the argument 'AutoStart=TRUE' to the function 'DAQmxWriteBinaryI32'. I will try your suggestion of manually starting/stopping the task.

Ian

[sergesl]

OK Ian,

Let me know how it goes.

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@I B wrote:
Hello Serge,

1. The documentation states, "If you do not configure the buffer size using DAQmxCfgOutputBuffer, NI-DAQmx automatically configures the buffer when you configure sample timing". So the buffer can be manually allocated using 'DAQmxCfgOutputBuffer'. The error still occurs regardless of whether the buffer is manually/automatically allocated.

2. The task is supposedly automatically started/stopped by passing the argument 'AutoStart=TRUE' to the function 'DAQmxWriteBinaryI32'. I will try your suggestion of manually starting/stopping the task.

Ian

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