Please help me on error -200284 for usb6008 data A/D

Question

Hi,
I am working on the A/D using usb6008, I program in visual c++.  I create a dialog to test the function of sample program: contAcquireNChan.c               in  NI-DAQmx Base.  I just changed the mode to DAQmx_Val_FiniteSamps and each time I just want to get several data. I used a button to start the a/d. The following is the code. The problem is very strange that while I click the start button for the sixth time, this error -200284 will occur when calling this function:
 DAQmxErrChk (DAQmxBaseReadAnalogF64taskHandle,pointsToRead,timeout,DAQmx_Val_GroupByScanNumber,data,2,&pointsRead,NULL));
The discription of this error is:
"Some or all of the samples requested have not yet been acquired.
To wait for the samples to become available use a longer read timeout or read later in your program. To make the samples available sooner, increase the sample rate."
I do not know what happened. And how to solve this problem. Please help me.
The following is the code:
void CBTTest001Dlg:nStart()
   // Task parameters
    int32       error = 0;
    TaskHandle  taskHandle = 0;
    char        errBuff[2048]={'\0'};
    time_t      startTime;
    bool32      done=0;
    // Channel parameters
    char        chan[] = "Dev1/ai0";
    float64     min = -10.0;
    float64     max = 10.0;
    // Timing parameters
    char        clockSource[] = "OnboardClock";
    uInt64      samplesPerChan = 2;
    float64     sampleRate = 2000.0;
    // Data read parameters
    #define     bufferSize (uInt32)1000
    float64     data[bufferSize * 5];
    int32       pointsToRead = bufferSize;
    int32       pointsRead;
    float64     timeout = 10.0;
    int32       totalRead = 0;
 index++;
 if(index==6)
    int a =0;
 m_bWorkFlag = true; 
  double a1= data[0];
  double a2= data[1];
  double a3= data[2];
  double a4= data[3];
  DAQmxErrChk (DAQmxBaseCreateTask("",&taskHandle));
  DAQmxErrChk (DAQmxBaseCreateAIVoltageChan(taskHandle,chan,"",DAQmx_Val_RSE,min,max,DAQmx_Val_Volts,NULL));
  DAQmxErrChk (DAQmxBaseCfgSampClkTiming(taskHandle,clockSource,sampleRate,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,samplesPerChan));
  DAQmxErrChk (DAQmxBaseCfgInputBuffer(taskHandle,2000)); //use a 100,000 sample DMA buffer
  DAQmxErrChk (DAQmxBaseStartTask(taskHandle));
  DAQmxErrChk (DAQmxBaseReadAnalogF64(taskHandle,pointsToRead,timeout,DAQmx_Val_GroupByScanNumber,data,2,&pointsRead,NULL));
 //    printf("\nAcquired %d total samples.\n",totalRead);
  m_fAnalog1 = data[0];
  m_fAnalog2 = data[1];
  m_fAnalog3 = data[2];
  m_fAnalog4 = data[3];
  m_fAnalog5 = data[4];
  UpdateData(false);
  if(taskHandle != 0) {
//   DAQmxBaseStopTask (taskHandle);
   DAQmxBaseClearTask (taskHandle);
 return;
Error:
    if( DAQmxFailed(error) )
        DAQmxBaseGetExtendedErrorInfo(errBuff,2048);
    if( DAQmxFailed(error) )
        printf("DAQmxBase Error: %s\n",errBuff);

Answer 1

Dear Neal,
Thank you so much !!
"DAQmx Base was designed for use on operating systems other than Windows". Maybe that's the reason why I always met problems.  I am using windows now !! The only reason for me to use DAQmx Base is that it comes with the USB6008 device so that I think NI recommend to use it ! I also downloaded DAQmx from NI but I did not tried it (in fact it took me several hours to switch the firmware back to DAQmx Base ). I will try It now and tell you the result.
"You say that you thought you solved the issue but did you not?"
Yes.
" Did you add the stop task function before and that is what you thought solved the issue? "
Yes.
I started from the example and do some modifications. First I met -200284 error and I found it is the caused by wrong number of data to be read. I changed to finite namber data read.
Then I met sixth reading problem, at that time I use a button clicking to read the data.when I read for the sixth time, It will occur (I forgot the phenomena). I added a  stop task function and I thoought I solved the problem. I knew for a finite number data reading, stop function is not needed, but I do not have any other method so I tried it. "sixth reading problem" solved, but When I move the data reading function to ontimer function recently. The program will halt -- take 99% of CPU time after 30 second of reading (sometime several minutes, sometimes several seconds). If I move the start task back to OnInitialUpdate() function and cancel stop function, halt error will not occur but the data I read in not correct. That is the whole thing. The following is the code relative to the data read.
Initialization;
void Ctest2Dlg:nInitialUpdate()
   DAQmxErrChk (DAQmxBaseCreateTask("",&taskHandle));
  DAQmxErrChk (DAQmxBaseCreateAIVoltageChan(taskHandle,chan,"",DAQmx_Val_RSE,min,max,DAQmx_Val_Volts,NULL));
  DAQmxErrChk (DAQmxBaseCfgSampClkTiming(taskHandle,clockSource,sampleRate,DAQmx_Val_Rising,DAQmx_Val_ContSamps ,samplesPerChan));
Data read
void Ctest2Dlg:nTimer(UINT nIDEvent)
  if(taskHandle != 0)
     DAQmxErrChk (DAQmxBaseStartTask(taskHandle));
   DAQmxErrChk (DAQmxBaseReadAnalogF64(taskHandle,pointsToRead,timeout,DAQmx_Val_GroupByScanNumber,data,100,&pointsRead,NULL));
   DAQmxBaseStopTask (taskHandle);