Error with pulse train generation (PCI-6111)

[hanking3]

DAQmxCreateTask("",&AOtaskHandle);
DAQmxCreateTask("",&COtaskHandle);

CounterFrequency = 611;

DAQmxCreateAOVoltageChan(AOtaskHandle,"Dev1/ao0","",-10.0,10.0,DAQmx_Val_Volts,NULL);
DAQmxCreateCOPulseChanFreq(COtaskHandle,"Dev1/ctr0","",DAQmx_Val_Hz,DAQmx_Val_Low,0.0,CounterFrequency, 0.5);

DAQmxCfgDigEdgeStartTrig(COtaskHandle,"ao/SampleClock", DAQmx_Val_RisingSlope);
DAQmxCfgImplicitTiming(COtaskHandle,DAQmx_Val_FiniteSamps,512);

AORate = CounterFrequency/512*1000;

DAQmxCfgSampClkTiming(AOtaskHandle,"",AORate,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,2000);
DAQmxWriteAnalogF64(AOtaskHandle,2000,0,10.0,DAQmx_Val_GroupByChannel, pdAOBuffer, NULL, NULL);

While loop

{ 

DAQmxStartTask(COtaskHandle);

DAQmxStartTask(AOtaskHandle);

DAQmxWaitUntilTaskDone(AOtaskHandle, 2);

DAQmxStopTask(COtaskHandle);

DAQmxStopTask(AOtaskHandle);

}

Question: 

If CounterFrequency >= 611, then pulse train handled by COtaskHandle works fine. Otherwise I cannot see any pulse.

I will appreciate it very much if you can give me a solution.

I am using PCI-6111.

[Jordan F]

Hi,

The PCI-6111 should be able to output digital pulses at a frequency less than 611.  If you take out the analog output code do you see pulses being output?  You would need to add a waituntildone for the counter task (I do not think that you need this though with the analog task because it will always be longer than the counter task).  I would recommend to try out some examples to see if you can get the two tasks to work separately.

DAQmx C Examples
Start>>Programs>>National Instruments>>NI-DAQ>>Text Based Code Support

Do you see any errors when you select a sample rate of less than 611Hz (even 610Hz) for your counter task or is there just no ouput?  After looking at your code I do not see anything that stands out currently.  Also, after calculating the sample times you are under the 2 second timeout limit in the DAQmxWaitUntilTaskDone function.