Mutithreading

[Software_Monkey]

Hi,

Is the NiDAQ software threadsafe? I have created a task handle in one thread but when I try to use it in another thread it complains that the handle is invalid.

Is there a way round this?

Thanks

[Seth_B.]

NI-DAQmx is both thread-safe and capable of multithreading.

Traditional NI-DAQ is thread-safe, but is not capable of multithreading as every call blocks every other call.

NI-DAQmx Base is not thread-safe.

What application development environment are you using? (LabVIEW, C# in Visual Studio 2008, etc)

Does your application deterministically guarantee that the task will be created before the handle is used elsewhere?

Regards,

[Software_Monkey]

Hi,

Thanks for the reply. I am using VC++ 6.0.

I create the task in the main thread, then set up a windows multimedia timer (which of course works in another thread) to do stuff with the task handle. I have assumed that the task it fully created and ready upon return from DAQmxStartTask(). It is after this call that I set up the timer.

The code is similar to this (edited)

	if(DAQmxCreateTask("", &anaTaskHandle) < 0)
	{
		DebugOut("Error:Failed to create analogue input task\n");
		return FALSE;
	}
	
	DebugOut("Info:Analog input task created for PCI6220\n");
	if(DAQmxCreateAIVoltageChan(anaTaskHandle, "Dev1/ai0:7", "", DAQmx_Val_Cfg_Default, -10.0, 10.0, DAQmx_Val_Volts, NULL) < 0)
	{
		DebugOut("Error creating analog input channels\n");
	}

	DAQmxStartTask(anaTaskHandle);
	
	// Set up the digital outputs
	if(DAQmxCreateTask("", &digTaskHandle) < 0)
	{
		DebugOut("Error:Failed to create digital output task\n");
	}

	DebugOut("Info:Digital output task created for PCI6220\n");

	if(DAQmxCreateDOChan(digTaskHandle, "Dev1/port0:1", "", DAQmx_Val_ChanForAllLines) < 0)
	{
		DebugOut("Error creating digital output channels\n");
		return FALSE;
	}

	DAQmxStartTask(digTaskHandle);	// Start the task running

	bool bTimerStatus = StartTimer(1);
	DebugOut("Timer resolution is %d\n", wTimerRes);
	DebugOut("Info:InitialiseHardware() succeeded\n");

 

I get the same invalid handle error each time the timer fires.

I hope this helps, I am a newbie to NiDAQmx.

Thanks

Tony