output Digitalwaveform

[dknovick]

Running in Windows 7 64bit

Compiling in Visual Studio 2008 Professional Edition

using the NI PXIe-6363 card

I can create the Digital waveform no problem.  My problem arises when I try to use BeginWriteWaveform to put the writing of the waveform in the background.

All of this in the attached zip, but I'll reproduce it here, I'm setting up 2 channels to output some digital pulses.

Here's how I set up the task:

        private const string TRIGGER_CHANNEL = "PXI1Slot2/port0/line0";
        private const string TTL_A_CHANNEL = "PXI1Slot2/port0/line1";
        private const string TTL_B_CHANNEL = "PXI1Slot2/port0/line2";


           signalTask = new Task();

           signalTask.DOChannels.CreateChannel(
                TRIGGER_CHANNEL,
                "Signal",
                ChannelLineGrouping.OneChannelForEachLine);

            signalTask.DOChannels.CreateChannel(
                TTL_A_CHANNEL,
                "TTL_A",
                ChannelLineGrouping.OneChannelForEachLine);

            signalTask.Timing.ConfigureSampleClock(
                "",
                signalClock,
                SampleClockActiveEdge.Rising,
                SampleQuantityMode.FiniteSamples);

            signalTask.Control(TaskAction.Verify);

            signalTask.Stream.WriteRegenerationMode = WriteRegenerationMode.DoNotAllowRegeneration;
            
            signalWriter = new DigitalMultiChannelWriter(signalTask.Stream);
            signalWriter.SynchronizeCallbacks = true;

            signalCallback = new AsyncCallback(SignalCallback);

and here is how I output the waveform:

        private void btn_Start_Click(object sender, EventArgs e)
        {
            Int32 signals = signalTask.DOChannels.Count;
            DigitalWaveform[] wave = new DigitalWaveform[signals];
            int pulse = (int)numE_pulse.Value;
            int samples = pulse * 4;

            for (int i = 0; i < signals; ++i)
            {
                wave[i] = new DigitalWaveform(samples, 1, DigitalState.ForceDown);

                for (int j = 0; j < pulse; ++j)
                {
                    wave[i].Signals[0].States[j + i*2] = DigitalState.ForceUp;
                    wave[i].Signals[0].States[(j + 2*pulse) + i * 2] = DigitalState.ForceUp;
                }
            }
            
            signalTask.Timing.ConfigureSampleClock(
                "",
                signalClock,
                SampleClockActiveEdge.Rising,
                SampleQuantityMode.FiniteSamples,
                samples);

            btn_Start.Enabled = false;


            signalWriter.BeginWriteWaveform(
                true,
                wave,
                signalCallback,
                null);


/*
            signalWriter.WriteWaveform(true, wave);
            signalTask.WaitUntilDone();
            signalTask.Stop();

            btn_Start.Enabled = true;
*/

If I comment out the section where I BeginWriteWaveform(), and uncomment out the section where I WriteWaveform(), WaitUntilDone(), and Stop(), I get the proper digital signal out.  So I know I'm creating the wafeform correctly.

If I do the reverse, and try to use the BeginWriteWaveform(), I don't get the proper digital signal out.  Usually one of the lines goes high, and never returns to zero.

Is there anything I'm missing?

[Michael-B]

Hello dknovick,

Have you been able to successfully run the shipping examples?  Do you see any strange behavior when running those?

[dknovick]

Thanks for the reply.

Can you point me to an example that might be similar?  These are the samples that were installed:

ContWriteDigChan_Burst - uses burst mode

ContWriteDigChan_PipeSampClk - interfaces to the NI 6536/7

ContWriteDigChan_PipeSampClokwHshk -  interfaces to the NI 6536/7

ContWriteDigPort_ExtClk - uses .WriteMultiSamplePort()

WriteDigChan - uses .WriteSingleSampleMultiLine()

WriteDigChan_ExtClk - uses .WriteWaveform()

WriteDigChan_WatchdogTimer - doesn't use a DigitalWaveform

WriteDigPort - uses .WriteSingleSamplePort()

-Dave

[Matt.M]

Hi Dave,

Do you know if your BeginWriteWaveform is finishing and calling SignalCallback?  I took a look at your code, and you seem to be calling everything properly, and if WriteWaveform works, then the async call should work also.

Regards, 

Matt

[dknovick]

---

@Matt.M wrote:

Hi Dave,

Do you know if your BeginWriteWaveform is finishing and calling SignalCallback?  I took a look at your code, and you seem to be calling everything properly, and if WriteWaveform works, then the async call should work also.

Regards, 

Matt

---

Thanks for double checking things.  I was pretty sure it was being called, since I disble the button before BeginWriteWaveform and enable it inside SignalCallback (one of my own tests to see if it was being called).  Just to be sure, I added a  1sec sleep inside SignalCallback before I enable the button.  And sure enough, with the code section around BeginWriteWaveform running, the button is disable, and then 1 sec later, it's enable again.

I was able to get this to work by creating my own asynchronous task.  I created a sendDigitalWaveform() function and a delegate function as well.  Then inside btn_Start_Click(), I create a new delegate, and then BeginInvoke().

Inside the function, I'm still doing:

WriteWaveform()

WaitUntilDone()

Stop()

...

Not very elegant.

-Dave