DAQmxGetTaskNumChans

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• Undefined function DAQmxSetAIADCTimingMode

  I have a creative process, installation, read and stop of typical task in VB6 code. The acquisition part is shown below. This code fails to compile when I include the call of synchronization (in bold). Sub or Function not found. If I remove the line in bold code runs correctly and acquires data. However, the default mode is HighResolution and I want HighSpeed.

  Note that all the functions and Mode Timing constants appear in NIDAQmx.h, and I can actually get this device work in high resolution or high speed mode using python. However I prefer not having to rewrite the entire VB6 application following a single function call if I can avoid it.

  So why this function is not? BTW - I use DAQmx 14.2 on Windows XP 32-bit

  ' create task

  DAQmxErrChk DAQmxCreateTask("", taskHandle)

  'Add an input thermocouple analog channel to the task.
  DAQmxErrChk DAQmxCreateAIThrmcplChan(taskHandle, "cDAQ-9214/ai:0", "", minTemp, maxTemp, DAQmx_Val_TemperatureUnits1_DegC, _)
  DAQmx_Val_ThermocoupleType1_J_Type_TC, DAQmx_Val_CJCSource1_BuiltIn, 25, "")

  ' set timing
  DAQmxErrChk DAQmxSetAIADCTimingMode (taskHandle, Ksystem.txtAIDev.Text, DAQmx_Val_HighSpeed)

  "Configure the task for the acquisition of the finished sample and read in the data."
  DAQmxErrChk DAQmxCfgSampClkTiming (taskHandle, "OnboardClock", frequency, DAQmx_Val_Rising, DAQmx_Val_AcquisitionType_FiniteSamps, numSampsPerChannel)

  "Set up needed memory space
  DAQmxErrChk DAQmxGetTaskNumChans (taskHandle, numChannels)
  arraySizeInSamps = numSampsPerChannel * numChannels
  ReDim data (arraySizeInSamps)

  "Start the task and to read the data.
  DAQmxErrChk DAQmxStartTask (taskHandle)
  DAQmxErrChk DAQmxReadAnalogF64 (taskHandle, numSampsPerChannel, timeout, fillMode, data (0), arraySizeInSamps, sampsPerChanRead, ByVal 0 &)

  "Call the StopTask module to shut down the DAQmx task.
  DAQmxErrChk DAQmxStopTask (taskHandle)
  DAQmxErrChk DAQmxClearTask (taskHandle)

  I managed to solve this problem and put the solution here in case its value to anyone.

  I ended up declaring the function and the call of the NIDAQmx (nicaui.dll) dll directly as follows. Worked a treat with a synchronization mode.

  Statement at the top of the form code

  ' original function header and enumerations can be found in NIDAQmx.h
  ' int32 __CFUNC DAQmxSetAIADCTimingMode (TaskHandle taskHandle, const char [channel], data int32);
  '
  Private Declare Function DAQmxSetAIADCTimingMode Lib "" nicaiu. "» DLL"(ByVal taskHandle As Long, ByVal channel As String, ByVal Val As Long) As Long
  Const DAQmx_Val_HighSpeed As Long = 14712
  Const DAQmx_Val_HighResolution As Long = 10195

  Function call

  "See the function DAQmxSetAIADCTimingMode in the top declaration
  DAQmxErrChk DAQmxSetAIADCTimingMode (taskHandle, myChannel, DAQmx_Val_HighSpeed)

• How to run the DAQmxGetTaskChannels command

  I'm reading the attributes of task of MAX by using various DAQmx with VB6 controls.  I found that a simple task of load (DAQmxLoadTask) generates a valid taskhandle of a known in MAX taskname that can be used to get the measurement data using the analog in the command "Read" (DAQmxReadAnalogF64).  The results seem to be already scaling according to my setup in MAX. What I want to do is read the names of the configuration tasks in MAX, select a VB and then read the names of channel and the ways of treatment of MAX and measurement data. I tried the following commands without error but still see a result null in the output string variable.

  DAQmxGetTaskName

  DAQmxGetTaskChannels

  DAQmxGetAICustomScaleName

  Curiously, the command, DAQmxGetTaskNumChans, book with success the number of channels in the setup of MAX.  With this information, I can get the measurement data, but I don't have the engineering units or the names of custom channel for my header output file to include with my measured data.

  I was wondering if the problem is related to incompatibility with newer versions of daqmx? Or maybe another reason?

  I use Windows XP, with service pack 6, a NOR-DAQmx 9.2.2 VB6 and NI DAQPAd-6015.

  Hi hutchins2,

  Thanks for posting, click on the link below that seems to be the reason for our problem:

  Textual DAQmx Device Information functions will return a NULL result

  Eric NOR

• How to exit properly ChangeDetection thread?

  I call the function ChangeDetection of the NI USB-6525 with C in a C++ program code:

  DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
  
  DAQmxErrChk (DAQmxCreateDIChan (taskHandle, "Dev1/port1/$line0", "", DAQmx_Val_ChanPerLine));
  
  DAQmxErrChk (DAQmxCfgChangeDetectionTiming(taskHandle,"Dev1/port1/line0","Dev1/port1/line0",DAQmx_Val_FiniteSamps,1));
  
  DAQmxErrChk (DAQmxRegisterSignalEvent(taskHandle,DAQmx_Val_ChangeDetectionEvent,0,ChangeDetectionCallback,));
  
  DAQmxErrChk (DAQmxGetTaskNumChans (taskHandle, & numLines));
  
  DAQmxErrChk (DAQmxStartTask (taskHandle));

  As far as I understand, this creates a separate thread that defines the USB box - 6525 ChangeDetection mode. When the unit detects a signal change, the C++ program calls a function (called ChangeDetectionCallback() in this case), which runs in its own thread (or perhaps the same thread, but in any case not the thread used to call the above code). It is explained here and is due to the argument of '0' in DAQmxRegisterSignalEvent().

  What I want to know is: while this thread is running (either one created by one of the above functions or whoever runs ChangeDetectionCallback() in), it is ok to quit the program? It could be any problem resulting from resources unfreed, for example? Are there measures should I take to make sure that everything completes successfully, as making sure always to call DAQmxStopTask() and DAQmxClearTask() before you quit the program?

  Hello

  If you click Exit, you must release all resources and the sons who have served in your program.

  You mentioned the right features, if you work with DAQmx, you must stop and cancel the task. If you work with threads (Thread Safe queue for example), it must be released, too. If you opened the file for playback of /writing, you must close them to provide the means and the free memory again.

  brinmr wrote:

  I call the function ChangeDetection of the NI USB-6525 with C in a C++ program code:

  DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
  
  DAQmxErrChk (DAQmxCreateDIChan (taskHandle, "Dev1/port1/$line0", "", DAQmx_Val_ChanPerLine));
  
  DAQmxErrChk (DAQmxCfgChangeDetectionTiming(taskHandle,"Dev1/port1/line0","Dev1/port1/line0",DAQmx_Val_FiniteSamps,1));
  
  DAQmxErrChk (DAQmxRegisterSignalEvent(taskHandle,DAQmx_Val_ChangeDetectionEvent,0,ChangeDetectionCallback,));
  
  DAQmxErrChk (DAQmxGetTaskNumChans (taskHandle, & numLines));
  
  DAQmxErrChk (DAQmxStartTask (taskHandle));

  As far as I understand, this creates a separate thread that defines the USB box - 6525 ChangeDetection mode. When the unit detects a signal change, the C++ program calls a function (called ChangeDetectionCallback() in this case), which runs in its own thread (or perhaps the same thread, but in any case not the thread used to call the above code). It is explained here and is due to the argument of '0' in DAQmxRegisterSignalEvent().

  What I want to know is: while this thread is running (either one created by one of the above functions or whoever runs ChangeDetectionCallback() in), it is ok to quit the program? It could be any problem resulting from resources unfreed, for example? Are there measures should I take to make sure that everything completes successfully, as making sure always to call DAQmxStopTask() and DAQmxClearTask() before you quit the program?

  Best regards, Fabian