DAQmx task is accessing a line it was never configured for?

[CurtisHx]

      using (NationalInstruments.DAQmx.Task writeClockTask = new NationalInstruments.DAQmx.Task("Write Clock Task"))
      {
        writeClockTask.DOChannels.CreateChannel("PXI1Slot6/Port3/Line5", "Clock", ChannelLineGrouping.OneChannelForEachLine);
        writeClockTask.Timing.ConfigureSampleClock("", 20000, SampleClockActiveEdge.Rising,
          SampleQuantityMode.FiniteSamples, digitalSampleCount);

        DigitalSingleChannelWriter clockWriter = new DigitalSingleChannelWriter(writeClockTask.Stream);
        clockWriter.SynchronizeCallbacks = true;

        readDataTask = new NationalInstruments.DAQmx.Task("Read Data Task");
        readDataTask.DIChannels.CreateChannel("PXI1Slot6/Port3/Line3", "Data", ChannelLineGrouping.OneChannelForEachLine);
        readDataTask.Timing.ConfigureChangeDetection("PXI1Slot6/PFI5", "PXI1Slot6/PFI5", SampleQuantityMode.FiniteSamples, 16);
        readDataTask.DigitalChangeDetection += (s, e) =>
        {
          Console.WriteLine("Digital change detection detected.");
        };
        //dataReader = new DigitalSingleChannelReader(readDataTask.Stream);
        //dataReader.SynchronizeCallbacks = true;
        //dataReader.BeginReadWaveform((digitalSampleCount - 1) / 2, new AsyncCallback(CallBack), readDataTask);
        readDataTask.Start();

        clockWriter.WriteWaveform(true, clockWaveform);
        writeClockTask.WaitUntilDone();
      }

I have the above code, where I'm trying to simultaneously write a waveform on PXI1Slot6/Port/Line5, and sample data on PXI1Slot6/Port3/Line3.  However, the event handler for readDataTask.DigitialChangeDetection is throwing a DaqException:

NationalInstruments.DAQmx.DaqException was unhandled
  Error=-201020
  HResult=-2146233087
  Message=Lines specified do not support change detection.

Select lines that support change detection.

Channel: port4/line5

Task Name: Read Data Task

Status Code: -201020
  Source=NationalInstruments.DAQmx

Notice that the channel is port4/line5.  Why?  I haven't configured the tasks for go after port4/line5, so why is that causing this code to throw an exception?

I'm using a PXIe-6535 digital IO module 

[CyanRyan]

CurtisHx,

in your configure line you specify a PFI line to use for the rising and falling edges.  

readDataTask.Timing.ConfigureChangeDetection("PXI1Slot6/PFI5", "PXI1Slot6/PFI5", SampleQuantityMode.FiniteSamples, 16);

The fuction itself is actually looking for a specific line call such as when you created the channel earlier.

"PXI1Slot6/Port3/Line5"

Odds are its getting to this line and is not sure how to use PXI1SLOT6/PFI5 so it is just assigning it to port4/line5.

I cannot find a text text based example that shows this, but using the example at the bottom of the link below shows some of the fommating for the ConfigureChangeDetection function. 

http://www.ni.com/white-paper/4102/en/

Hopefully this helps you out,

CyanRyan