Share reference clock between different tasks?

[lcm0]

I can't really find helpful information about how the sample clock is internally used/blocked. For example I configured a task to continuously read von Dev1/port0/line7 via the SampleClock event

var myTask = new NationalInstruments.DAQmx.Task("Emergency stop button task");
var diChannel = myTask.DIChannels.CreateChannel(
    device.DeviceID + "/port0/line7",
    "",
    ChannelLineGrouping.OneChannelForEachLine);
diChannel.DigitalFilterEnable = true;
diChannel.DigitalFilterMinimumPulseWidth = 10.24e-6;
myTask.Timing.ConfigureSampleClock(
    "",
    1000.0,
    SampleClockActiveEdge.Rising,
    SampleQuantityMode.ContinuousSamples
);
myTask.SampleClock += myTask_SampleClock;
var myReader = new DigitalSingleChannelReader(myTask.Stream);

...

void emergencyStopButtonTask_SampleClock(object sender, SampleClockEventArgs e)
{
    bool val = myReader.ReadSingleSampleSingleLine();
    Console.WriteLine(val);
}

This works just fine. Now I want create a second task, that waits for rising edges on Dev/port0/line6. The code is as follows

var mySecondTask = new NationalInstruments.DAQmx.Task("Proximity switch task");
mySecondDIChannel = mySecondTask.DIChannels.CreateChannel(
    device.DeviceID + "/port0/line6",
    "",
    ChannelLineGrouping.OneChannelForEachLine
);
mySecondDIChannel.DigitalFilterEnable = true;
mySecondDIChannel.DigitalFilterMinimumPulseWidth = 10.24e-6;
mySecondTask.Timing.ConfigureChangeDetection(
    device.DeviceID + "/port0/line6",
    "",
    SampleQuantityMode.ContinuousSamples
);
mySecondTask.SynchronizeCallbacks = true; 
mySecondTask.DigitalChangeDetection += new DigitalChangeDetectionEventHandler(mySecondTask_DigitalChangeDetection);

...

void proximitySwitchTask_DigitalChangeDetection(object sender, DigitalChangeDetectionEventArgs e)
{
	Console.WriteLine("Change event detected");
}

If I try to execute the code, I get the error "Specified route cannot be satisfied, because it requires resources that are currently in use by another route." I guess it's about the sample clock that is blocked by the first task. Why cant the second task use another clock? Can I share the clock between the tasks?

I mean it should be quite simple...!? But I have no clue where to find the informations to understand/solve the problem on my own. I found this http://digital.ni.com/public.nsf/allkb/3D99C0ECBCC9FA9C862576E800556235 but I can't apply this to .NET/C#.

Edit: I can't even set the clock source for the digital change detection. How do I do so because ConfigureChangeDetection() won't let me.

[JGoebel]

Hi Icm0,

what type of Device are you currently using? And what do you need the changedetection-path for?

I wouldn't be sure, that its about the sample clock, because you dont use a sampleclock with a change detection timing. The "sampleclock" for Changedetection is the Signal you are trying to detect changes in.

Regards,

Jan Göbel

Applications Engineer

[JGoebel]

*changedetection-task (not path 😉

[JGoebel]

Hi Icm0,

i have to correct myself. The Changedetection-Task does need a SampleClock. I assume you are using a cDAQ-Chassis with a DI-Module. Usually cDAQs only have one di/sampleclocktimebase. This means you can only specify one di/sampleclock. So you can only use one timed DI-Task with the whole device (even if you got 2 modules).

My approach would be, to do a normal timed DI-Task with all channels you want to monitor, and to realize the changedetection within your Program.

Best Regards,

Jan Göbel

Applications Engineer