Root Loop, Time/Date Browse and DAQmx Watchdog

I've just run into the issue where the time/date browse calendar control blocks execution of my system. See here for discussion about this problem.
I've got a data aquisition loop running that uses the DAQmx watchdog, and opening that browse window is causing my watchdog to starve, thus causing my application to shut down. Curiously, when I open drop down menus, as Jack illustrates in the aforementioned thread, I do not see the same behavior. It's not really clear to me what is causing it to block, but the dropdowns don't.
I'm wondering if anyone has any further explanations, or suggestions for workarounds.
Tim Elsey
LabVIEW 2010, 2012
Certified LabVIEW Architect
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One solution I did in the past to solve this was to create my own Data/Time dialog in LabVIEW and hide the native button and add a normal button to the front panel which invoked this dialog. Since that makes the dialog a normal VI the root loop problem is not present with that. There is a VI in resource/dialog/picktime.vi that looks like the dialog used in the date/time picker but it isn't since making changes to this VI won't appear in the native dialog. LabVIEW seems to use an internal C implemented dialog which is the root cause of the root loop being blocked since the dialog message handler is running in the same thread as the root loop.
Creating a copy of this VI in your own project and adding it through your own custom time browse button should solve the problem.
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Similar Messages

Detect if time/date browse button was used

Hi,
I have a position control vi for indexing elements inside array and displaying corresponding time and date. I have large number of control signals inside my block, but I have removed all irrelevant blocks and signal for this discussion. I have replaced all unnecessary controls with constant values, so don't waste time analyzing it.
If you take a look at my vi, you will see Star/Stop control, Position control and a time stamp indicator (Waveform time) with a time/date browse button from another time stamp control. I have all desired functionalities, but I have problem when using browse button for setting up time. I can't set my time two times in a row at same value because I'm comparing "Last entered time stamp" value with current one just entered. I would not like to completely change my blocks because I'm using a lot of property nodes and variables inside my project. I'm just looking for a way to figure out if time/date browse button has been pressed so I could jump to desired point in my recorded waveform.
Solved!
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Attachments:
position_control_lite.vi ‏16 KB

I can't change Waveform Time Indicator to a Control because that would make other controls much complex (not shown in attached vi)
I have modified my block to the simplest form. I have changed some control names.
There is now only one problem - how can I detect if user has pressed time/date browse button? I'm not interested at this point which value has been entered.
I need to replace User has entered value in Jump to time/date with some kind of Boolean logic or event case.
Message Edited by _thomas on 11-17-2009 09:23 AM
Attachments:
position_control_lite_lv8.6.vi ‏14 KB
position_control_lite_lv8.0.vi ‏19 KB
position_control.png ‏33 KB

Change language of time/date browse button

Hi. How I can change the language of time/date browse button. For example,
i want to change the caption of button "Set time to Now", to the "Time"? Is it possible?
Thanx.
Solved!
Go to Solution.

The dialog is a VI that is part of the LabVIEW package.
You can make a copy of this VI and edit the button text as you want.
look for picktime.vi in your \resource\dialog\ subdirectory of your LabVIEW installation.
Now is the right time to use %^<%Y-%m-%dT%H:%M:%S%3uZ>T
If you don't hate time zones, you're not a real programmer.
"You are what you don't automate"
Inplaceness is synonymous with insidiousness

How can I open the 'time date browse button'?

Hello!
How can I open the 'time date browse dialog' from the time stamp control in my block diagram? I tryed it with the property node but couldn't find this item to open the 'time/date browse dialog'!
Thanks in advance for your help

There is no way to programitically bring up the dialog window for the timestamp control. I recommend building your own dialog window VI that will work by opening when you want the user to set the time and when it closes, it can programatically update the timestamp control. It will not be as pretty but it will be just as functional.

Slow loop times with 6024E and LV2009

Hello all,
I have searched the forums back and forth, in addtion to the knowledge base, but I am still confused as to the slow loop times I am experiencing. I have a 6024e PCMCIA DAQ card with a very simple VI created in LV 2009. I am using the DAQ Assistant to collect 1 thermocouple channel on a SCXI Chassis 32 channel thermocouple module.
The problem is that the loop times in labview is about 3 seconds. The DAQ Assistant acquisition mode is set to "on demand". The target sample rate is about 1 to 2 samples per second. I have read in previous posts that the repeated creation of the task using the DAQ Assistant with the acquisition mode set to "on-demand" can slow things down.
What really has me confused is that using this exact same method of setting the DAQ Assistant acquisition mode to "on-demand" has worked fine on the same hardware when using one of the earlier v8 versions of LabView. I don't understand what has changed and why the loop times are so much slower. I planned to pull the newest LV2009 off the computer and put a previous v8 version on just to confirm my observations. In addition, I pulled up a copy of the VI that was written in one of the v8.x versions and it used the DAQ Assitants with the acquisition mode set to "on-demand" and had a loop time of 0.100 seconds.
Any help would be appreciated. I have been working on this all day today with no sucess.
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H_baker,
I did have the patch applied at the time I was experiencing the problems. The DAQmx driver version was the version that was supplied on the DVD that we received for LV2009. I believe the actual version number was something like 8.9.5.
The loop time was determined as follows:
A simple vi I was written in a while loop. The data acquisition was conducted using the DAQ assistant sampling 1 channel on the SCXI thermocouple module in a SCXI 1000 chassis. Inside the loop of the vi the getdatetime function was placed and wired to an indicator on the screen. The vi was then ran. Observation showed that the loop time was typically 3 seconds and sometimes 6 seconds by keeping track of the datetime indicator on the front panel.
The problem appears to be resolved now. I had pulled off the LV2009 installation and put back on the 8.6 installation. Recreated the vi and everything worked fine. As a sanity check I went ahead and reinstalled LV2009. Recreated the vi again and everything works fine now. The only real difference between the two installations is that I am using the latest NIDAQmx drives (I believe version 9.0.5). It could have been just some sort of transient issue that resolved itself either by reinstallation or by rebooting. Not sure. I was just initially very concerned given that another posting had mentioned loop times of 3 seconds just like I was experiencing.
Thanks,
Steve

SIT Real-time data logging and passing data

Hello all,
I am pretty new to LabView real-time, so I just want to confirm a few things. I am also using the Simulation Interface Toolkit.
Let's take the Sinewave.vi from the SIT examples. I have modified it to use sinewave.dll, and run on PXI-8101. If my understanding is correct, when I click "Play", the entire Sinewave.vi is deloyed into PXI-8101, and therefore the entire VI is running at the same pace. The front panel I see on my desktop is slower snapshots of what is actually happening?
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Attachments:
Sine Wave.vi ‏104 KB

Hi Bladhart,
When running the in the Development Environment (pressing the run button on the Real-Time vi) there will be an extra thread to handle the front panel you see. This thread will be handled just like any other thread in Real-Time and will take processor time, thus slowing down your entire application to a certain extent.
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<Brian A | Applications Engineering | National Instruments>

Different loop times

Hi,
I have a timed loop with 500ms loop time for Counters and Analog
Buffered reads. The control loop has a 20ms loop time. Is it possible
to read from the buffer, using DAQmx Read in these two loops, without
altering the current read position in the buffer?
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Roger Isaksson, Damill AB

Hello Roger!
I believe this question is under control now after the last e-mail conversation we had!
Good luck with your project!
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Applications Engineer, National Instruments
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I noticed that along the top bar, my date was not reading the way it should. Instead of 5/4/2010, it reads 3 5 4 (with the spaces there). So, I right click on the time/date and select time & date preferences, and instead of opening, it takes me to a 'system preferences quit unexpectedly' where I have 3 choices, 'show details' which opens a long data screen, with a space for me to type in what I supposed happened, an 'ok' button, that just closes the error screen, and a 'reopen' button which takes me to the system prefs page, and if I click on the date/time icon there, it just takes me back to the **** quit unexpectedly screen. So? HELP!
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Best way to capture data every 5 ms (milli-seconds) in the .vi diagram when using "Time between Points, and Small Loop Delay tools" ?

- Using LabView version 6.1, is there anyway to change the "Time Between Points" indicator of (HH.MM.SS) to only (mm.ss), or to perhaps only (.ss) ?
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I have no idea what "Time between Points, and Small Loop Delay tools" is. If this is some code you downloaded, you should provide a linke to it. And, if you want to acquire analog data every 5 milliseconds from a DAQ board, that is possible with just about every DAQ board and is not related to the version of LabVIEW. You simply have to set the sample rate of the DAQ board to 200 samples/sec. If it's digital data, then there will be a problem getting consistent 5 msec data.

Continuous data acquisition and analysis in real time

Hi all,
This is a VI for the continous acquisition of an ECG signal. As far as I understand the DAQmx Analog read VI needs to be placed inside a while loop so it can acquire the data continously, I need to perform filtering and analysis of the waveform in real time. The way I set up the block diagram means that the data stays int the while loop, and as far as I know the data will be transfered out through the data tunnels once the loop finishes executing, clearly this is not real time data processing.
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Any advice would be appriciated.
Solved!
Go to Solution.

You have two options:
A. As you mentioned, you can place code inside your current while loop to do the processing. If you are clever, you won't need to place another while loop inside your existing one (nested loops). But that totally depends on the type of processing you are doing.
B. Create a second parallel loop to do the processing. This would decouple the processes to ensure that the processing does not hinder your acquisition. See here for more info.
Your choice really depends on the processing that you plan to perform. If it is processor-intensive, it might introduce delays as you mentioned.
I would reccomend you first try to place everything in the first loop, and see if your DAQ buffer overflows (you can monitor the buffer backlog while its running). If so, then you should decouple the processes into separate loops.
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Send analog trigger every time data is acquired and saved

I am currently writing a program that acquires and calibrates data from 32 channels of force plates. Once the data is acquired and calibrated it is saved to a file. I need to send a pulse to another computer running labview once every time data is acquired and saved. I have written several versions of this code that send a continuous pulse train while data is being saved. I need to modify the code so that it does not send a continuous pulse, but an individual pulse that is a set frequency every time I acquire data. I believe that I need to use a software trigger to control the pulse, but I can't seem to find a way to have the hardware send a pulse only when I want it to.
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Actually after tinkering with it for several hours I managed to figure out a way to solve my problem. I'll explain it in case anyone else has a problem.
What the software does: The software is an acquisition loop that outputs a square wave pulse of finite frequency to another acquisition system at the beginning of each acquisition iteration while data is being saved. This is so that the data from the two systems can be synchronized later.
The program flow is this Send Single Synchronization Pulse-> Acquire Data->Calibrate Data->Save Data to file->Repeat
The pulse is triggered once data begins saving, but the device begins acquiring data on execution of the software.
To do this I set up the DAQmx Channl configuration to CO Pulse frequency. I then set the timing up to be finite iterations and the number of iterations to 1. Inside the acquisition loop I enclosed the whole acquisition process in a flat sequence. In the first sequence, if the program is saving data it turns the pulse on, if not saving the task passes through. The acquisition occurs in the middle sequence and in the final sequence if saving the task is turned off. If not saving the task passes through. This allowed me to send one pulse of a finite frequency every time the loop is run.
Thank you very much for your response though. If anyone else runs into a problem like this I can post a screenshot for future reference when I get a chance. Thanks again.

Root Loop, Time/Date Browse and DAQmx Watchdog

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