Clear task handle

hi
My application needs to clear the existing task handle
before creating another task.
i need acheive this, how can i find the task handle "id"
and clear that.
do let me know.
regards
rags

DAQmxClearTask
int32 DAQmxClearTask (TaskHandle taskHandle);
Clears the task. Before clearing, this function stops the task, if necessary, and releases any resources reserved by the task. You cannot use a task once you clear the task without recreating or reloading the task.
If you use the DAQmxCreateTask function or any of the NI-DAQmx Create Channel functions within a loop, use this function within the loop after you finish with the task to avoid allocating unnecessary memory.
The task handle is the same value of type TaskHandle you used when you created the task
Elijah Kerry
Senior Product Manager, LabVIEW
Follow my Software Engineering for LabVIEW Blog

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Global tasks (handler)

I have programmed legacy DAQ cards like the 6024 using LabWindows CVI for 15 years. Now I have to use a USB 6218 and DAQmx. I want to use a counter to measure my loop time. If I start a task (like start the counter) in one subroutine call I can not call that same task in another subroutine call (like read the counter). The task handler ID seems to only be a local variable. The task or taskhandler can not be made a global variable. If the create, start, read, stop, and clear tasks are all in the same subroutine, everything works. I hope I am stating this problem correctly, I am an engineer who knows some programming, not a pure programmer.

RobertoBozzolo,
First of all, thank you kindly for your quick response and help. I think you are onto the source of my problem. I have attached some information to explain the code. The program is very large. I thought I have defined the Task Handler at the system level with a static definition. But when I compile the code, I get a message that the task handler is undefined.
I hope I have explained my code in the attachecment well enough for you to see the problem.
I have to share with you that I have never used task handlers. Somehow, since CVI was started I have gotten by without out it. Right now I am not a fan of the DAQmx approach to data acquisition and control. I used to be able to use simple easy IO or legacy library routines that were very straight forward and used a minimum of code. I also tried defining the tasks in Measurement and Automation Explorer, but I could not get those to work also. I thought it was just me but I talked to two other engineers who also dabble in programming and they too are not happy with the improvement.
I think the issue is that we have to be better programmers. Instead of just engineers who use the CVI tool.
Again, I want to thank you for any help that you can offer.
Mike
Attachments:
Taskhandler issue.docx ‏22 KB

Several DAQmx Channels with Start and Clear Task VI's

Hi,
I'm trying to read in several DAQmx channels in a while loop. When I just place the channels within the while loop and connect them directly to the read VI's, everything is fine. But I read in the help, that this will slow down my system, because it's opening and closing the task each cycle. So I used Start Task and Clear Task VI's to open and clear them before and after the loop. But now it's only reading one of my channels in, although I wired all of them in exactly the same manner. Anyone has an idea, what I did wrong?
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Attachments:
Save&Stop DAQ.JPG ‏87 KB

You would have seen the error if you had wired up and error indicator.
You cannot run multiple tasks of the same type (i.e. an analog input) at the same time. What you read about stopping and closing tasks is correct but it was the only way your program could work. What you don't realize is that you can have multiple channels with a single task. If you used a physical channel constant, it would be something like 'dev1/ai0:2' if you had consecutive channels or 'dev1/ai0, dev1/ai2' for non-consecutive. Global channels are done in a similar fashion. You would have 'FSR1, FSR2, Knee Angle', etc.

How to get running Daqmx task handles

HI,
We are creating a TestStand module using CVI 8.5, in that module we have to close all the running Daqmx tasks, please provide help on how to get running Daqmx task handles. We could not find any API function which can return list of running Daqmx task handles so that we can close one by one.
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I just had a similar issue. Stumbled on this forum in the hopes of getting an answer and found no reply to the original message. I think this is what we are both looking for DAQmxGetSysTasks.
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Clear Task Error

Hi,
i use DAQmx Create Channel.vi's to create 3 Channels: one of them as differential- so i have 2 (later maybe 3) tasks. Problem is, when i start my VI, i get error how some task resources are reserved, but i use Clear task?!?
Here is my application.
p.s.: Why not DAQmx Assistent Express? Because i need to change the sampling rate online.
Thanx in advance
Vedran D.
Attachments:
Uff_10_05.vi ‏119 KB

Dear vedran,
You have to combine measurements of the same type into one task.
To understand better please have a look at the following links:
Why Do I Get Error -50103 When Using Multiple DAQ Assistant Express VIs?:
http://digital.ni.com/public.nsf/websearch/04BEDD9E9E91ED3486256D180048116D?OpenDocument
NI-DAQmx: Creating an Analog Input Task with Multiple Measurement Types:
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=CA272F2D99585A8AE034080020E74861&p_node=200509&p_source=External
I slightly modified your VI (attached). Now it should work but with your card you're not able to change the sample rate of these measurements seperatly.
Best regards
Attachments:
Uff_10_05(modified).vi ‏101 KB

Stand-Alone application with LabView 7.0 getting error can't find DAQmx clear task.vi

I have attempted to create a stand alone vi with the Build Application or Shared Library(dll) in LabVeiw 7.0
When I put it on another PC to test it I get the error "can't find DAQmx clear task.vi"
the other PC has Labview 7.0 and DAQmx 8.1 also.
I believe my problem is in the source tab where you are supposed to add support and dynamic vi's I have search the forums and Ni's data base and have not found a solution.
Solved!
Go to Solution.

Hi LabTech09,
When you run the executable on the other computer is when you get this error? Do you have the exact same versions of LabVIEW and DAQmx on both computers? Does the dialog allow you to navigate to the DAQmx clear task.vi? If so, you can find these VIs in C:\Program Files\National Instruments\LabVIEW 7.0\vi.lib\DAQmx\configure\task.llb. Does the executable work on the development machine (the machine it was compiled on)?
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Jim Schwartz

Does performing a DAQmx Clear Task on a PCI-4474 card change the state of the IEPE current?

Does performing a DAQmx Clear Task on a PCI-4474
card change the state
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settle if I make a new Task and start a new measurement--is this
correct?
Thank you in advance for your help.
Ken

DAQmx Clear Task should not turn off IEPE current. You will have to explicity set IEPE current to On (for that channel) whenever you use any of the AI channels on your 4474 in order to keep the IEPE On because the IEPE for all channels in the AI subsystem will be set to the default state (Off) unless explicitly configured. That said, if you clear a task that had IEPE On, and then initialize a new task and set IEPE On, the IEPE will be uninterrupted and there should be no need to wait for the IEPE to settle. Other components of your measurement system might need time to settle if their state was changed between tasks (DUT, sensor, AC coupling, etc.)
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Disable J2EE Local Auth Task Handler in policy agent 2.2

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Is there a way of disabling the j2ee local authentication handler for a policy agent 2.2 running in filter mode ALL ?
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Hi Gurus,
Need your help on the following queries:
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Hi,
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Sonny:
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Task handler faults

I'm in the process of migrating my 10.1.2 beta 3 sources to the GA version but have encountering faults associated with human workflow. I'm experiencing the error with migrated tasks and newly created ones. I still haven't retrieved the referenced patch as I'm working on metalink access.
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initiateTaskActionHandler (faulted)
[2005/05/24 10:44:41] "{http://schemas.oracle.com/bpel/extension}bindingFault" has been thrown. less
<bindingFault xmlns="http://schemas.oracle.com/bpel/extension">
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</part>
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Could you please mail me your Beta project files at [email protected] (zip it and rename to .zipr). And do let me know the steps to replicate.

EJB3 long running task handling

Dear all,
Please help me on this,
We developed application using struts2 ejb3webservice.runing on jboss5.
This is a hotel reservation system. User make a request to get the hotel listing that is available, ejb3 Stateful get the connection to the web service and retrieve the hotels and process with the pricing then send back to the struts to display it to user. This happens only once for a search. The problem here is the EJB processing takes lots of time if it is more hotels available.
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Is this correct solution? If so how can I implement such a thing using EJB? any suggestion please?
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I am not a struts expert but I think that if you want a background processing you should use a Message Driven Bean.
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How do I get the Handle of an Existing Task?

I'm using a National Instruments board with Matlab. This is allowing me to perform interactive command-line development. But, I've run into an interesting problem. I can create a task and forget the handle. Now I cannot use the task (forgot the handle), but it is still allocated and I cannot re-use the task name (until I stop & restart Matlab). I realize this is sloppy programming and simply a result of me typing in DAQ commands one at a time from a command line, but - is there any way to return a task handle if the task name is known? I've searched for a function int32 __CFUNC DAQmxGetTask(const char taskName[], TaskHandle *taskHandle) but it doesn't seem to exist. Any chance you guys could write one and add it to the library? It would make interactive development through Matlab easier.

Hello bsimon,
It's been a while since I've programmed in Matlab and I've never used DAQmx in Matlab (in my experience, LabVIEW, CVI, C/C++, any of the .NET languages and even VB, though I hate it, would seem to be vastly superior ADEs because the DAQmx API actually supports these languages). In spite of my stated inexperience, if you are just making C function calls from the command-line, can't you just 1) directly access whatever variable you are currently passing in for *taskHandle OR 2) explicitly create a TaskHandle *taskHandle at the command line and just access this variable?
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DE For Life!

Problem clearing a task

Hello,
Thanks to a few of the members here, I am able to control the opening and closing of two digital water nozzles with DAQ hardware timing.
The way the application works is basically a 2-D array of boolean values is created based on the desired period and high time. The nozzle will open when the boolean value is true while it closes when the boolean value is false.
The only problem remain is that if the application stops when the last boolean value is "true", the water nozzle will remain open indefinitely. I believe that I am not using "clear Task" correctly. This is the most obvious when i set the high time = period so that the duty cycle is 100%. this way the array contain only "true" values. No matter how i stop the application, the nozzles won't turn off.
I have attached the application here and let me know if there are something wrong with the way I am ending the tasks.
I tried to keep this brief so if there are something I'm missing please ask.
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Attachments:
microsecond_nozzle2.vi ‏209 KB

With outputs, they will always retain the last value sent to them. Clearing the task does not reset them.
What you will need to do is write a set of all Falses to the task before you clear the task and end the program.
By the way, your use of the select function does nothing. (If true select true, if false select false). You can use the wire as is and eliminate the Select function and the true and false constants.
Message Edited by Ravens Fan on 09-09-2008 02:12 PM
Attachments:
microsecond_nozzle2[1]_BD.png ‏4 KB

TimeCapsule and CLEAR: I want TC to handle DCHP

I've seen this post on how to set up the TC as a bridge and let CLEAR handle DHCP: https://discussions.apple.com/message/11093142?messageID=11093142
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You don't want the TC to handle DHCP unless you can first configure the Clear modem as a "bridge". The reason is that you don't want to have two devices both handling DHCP on a network.....that will create even more problems.
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Clear task handle

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