Stopping at two simultaneously while loops in a sequence

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• Problem running two parallel while loops

  Hello world

  I'm new to Labview and is actually my first attempt. I intend to acquire data from two rockers simultaneously through two different ports. When I run my program attached with execution has highlighted, the second loop gets higher priority. How to prevent this? Also, I'm getting error codes when running arrives at the stage where Visa read data are passed to sweep of string function. Please suggest corrections to correct these problems.

  PS: I have not yet plugged on devices, that's why the properties of connection for the two Ports are the same at the moment.

  Kind regards

  Avi0111

  
  

• No simultaneous while loops

  Right, I have a two part program. The first generates a sine wave and exporting to an external device. The second part takes a camera input and performs calculations on the data and exports it in a spreadsheet.

  The problem I have is that the data is not saved with the frame rate of the camera (17fps), but at the level of the loop the first loop (10 per second). When I run the program separately camera part, I get the full 17 per second.

  I wish that both parties in a VI.

  So my question is, how can I get loops to run at the same time no?

  I would include my VI there a lot of complicated functions that do support any sense, but I think my question is fairly general. I'll be happy to give more details.

  Thanks to anyone who can give me some advice on this.

  James

  
  

• Start stop while loop with tab control

  I want to be able to start and stop a while loop by entering and leaving a tab.  I use a structure of the event to do so, but it seems not elegant or the right way to do it.  The only way I could get to the kind of work is by unchecking the lock front panel in case of structure.  I have attached a sample vi of what I have so far.

  The problem is that you can't even stop the program by pressing the stop button until you exit the tab, which is not a user friendly interface.

  The event should just manage basic user events.  Any given event does not take a lot of time to run.  While you are in the diagnostics tab, your code is stuck in this while loop.  Although the setting of the front panel of the lock allows you to do other things, the LabVIEW is just put on hold all these other events of the UI (like Stop button value change) and cannot handle them inside while the loop stops and allows outside while loop to go through again.

  You should have a parallel while loop to manage waveform graph.  You can use notifiers or queues or a motor of action FGV (see Ben Action Engine Nugget) to switch the starting or stopping of the update of the chart of waveform until the parallel of while loop.

• 2 parallel while loops with functional overall to share data

  Hello

  I'm having a problem with the sharing of functional with globals data between two parallel while loops:

  1. One of the loop (bottom) generates a random number periodically and write the total functional sample.
  2. Another loop (above) has a structure of event and when it expires, he would read the functional global and intrigue, a chart data point.

  The problem is sometimes the functional overall seems to be 'locked' and the output becomes zero constant. It also seems that whenever I first open the VI, it works fine. But for the second time running, he begins to have the problem.

  

  You must initialize your VI stop FGV FRONT of your lower loop begins.  Even if you use a global variable that is functional, you have a race condition.  FGV is read in the lower loop until it had a chance to be initialized with a value of false in the upper loop.  Functional global variables do not forget their data between executions of the VI.  So it is always set on stop the last time that you ran the VI.  This works your VI the first time it's because VI does not have in memory, so when it loads, it loads with the default value False in the shift register.

• Sharing of Boolean values across while loops

  I'm new to Labview and I try to use an angular encoder as a type of switch.

  I want to take measures continuously from the angle of the encoder and turn on an analog output signal, each time comes in a certain angle. When the encoder drops from this angle, I need the signal to turn off.

  To do this, I try to run two parallel while loops. We measure the angle of the encoder, while the latter creates the output signal. What I want to do is to put a logical statement in the measurement loop that will record 'true' if the maximum angle is reached. I try to get that 'real' statement in the loop of generation of signals as a trigger to turn on (using a case structure and the "DAQmx Start Task.vi") output. The question I have, is that the 'real' statement cannot exit the loop to measure up to the end of the loop. But since I'm running it continuously, the loop ends. Thank you.

  Create a local variable of the Boolean in anxiety.  Right-click on the local area and select change reading.  Put this inside the loop else local.  If you have a loop that writes to the Boolean value and a loop that reads from the local.  Now you can remove the wire that comes from a single loop and feeds on the other.  Then your curls will work in parallel (if there is no other dependencies of data between the two loops).

  As an alternative to local variables, you can use a queue to transfer data from one loop to the other.  A loop (the producer) will write to the queue.  The other loop (consumer) reads from the queue.  See the examples on the architecture of producer-consumer for more information.

• Data dependence isn't the only thing to stop while loops to run simultaneously?

  I write code to turn two stepper motors with various functions. This is my first program, so I don't know it's terrible, but I'm very interested in getting this work. I checked for the data depenecy and followed some suggestions to use local variables to solve the problem. It did not work, so now I'm trying to understand this.

  I know that all features were able to simultaneously run, but after a few changes (including put everything in a while loop to keep the program running until someone clicks the exit button), no function can currently work simultaneously.

  I'll post my code in case someone has the time to watch it (I'd really appreciate it if someone did), but I am also looking for any other problem that might be the source of the problem.

  Really, any help is greatly appreciated.

  Thanks in advance

  
  

• Code Golf: stop two while loops with guaranteed ratio iteration

  Proposal

  In the vein of the tradition of Perl, I would like to see if there is any interest to solve a few puzzles programming in LabVIEW. Can someone post a problem and define the rules to solve.

  Here's a question for beginning/intermediate to sharpen your "palette".

  Description

  With a user action, how you would stop two while loops such as the relationship between iterations is the still the same? Concrete to view this situation is to take action: both instruments use the same source of synchronization to take measures, but second divides the clock down so that it is a little slower than the first whole factor. For example, if the slower instrument is four times slower, then at the end of the VI, the slower instrument takes 100 measures the fastest instrument took 400.

  Rules

  • You can use vi.lib
  • You cannot include any other subVIs
  • Your solution should pass for loop1 interval as low as 25 ms

  Model (joint in LabVIEW 2009)
  

   

  If people are interested in this, then we will find a way to improve future problems. Please post your suggestions and criticisms, but only if you also post a presentation ;-)

  MacNorth wrote:

  [..]

  If we choose the first suggestions, the VI has yet to recover the data at different speeds. You can dedicate a loop for each instrument to disassociate a jitter and latency introduced by their connectivity or the inner workings. This adds a margin of safety when there is a conflict of thread and the pilot. You can also implement a simple counting as altenbach loop and renounce the multiloop complexity.
  [..]

  It is a very good point. But I wanted to make sure, you should / need to discuss the benefits, but also the disadvantages of the design. Implementation of an application is most often a process of 'special cases '. If a framework/design for a single application model does not necessarily correspond to another application.

  Designs are always strongly according to the requirements and constraints. What gives here designs will result in educational services, of course, but not necessarily as reference models for specific applications.

  Advantage of simple loop:

  • No synchronization between several loops required
  • Can easily implement any whole factor between services (quotent & function remains for a case structure

  Disadvantage of simple loop:

  • Take advantage of the multi core systems (at least not much)
  • Can easily run out of the time constraints (material not "not responding" enough, fast manipulation of data takes too long,...)
  • Code will accumulate within the structures of the case, where the readability could suff

  The advantage of multiple loops:

  • See essentially the disadvantages of single loop (several loops solve those)

  Disadvantage of multiple loops:

  • More complex, especially for the sync switch (not beginner friendly, requires a more/better design)
  • May contain easily questions source such as race conditions and locks

  A little side note:

  Even if the equipment works different acquisition rate, this does not necessarily that the software must use different rates for data extraction. You can use the same model of an hour, but get X times more values for the task faster than the slower running. The 'only' thing to care of are the sizes of buffers and bottlenecks in the data transfer.

  MacNorth wrote:

  [..] The best advice published OR shutter multiple while loops (https://www.google.com/search?q=labview+stop+multiple+while+loops) are laughable (and the 'solution' in my model). [..]

  No, it's not laughable. For many applications, this approach to shutter at the same time several loops running is OK. The constraint: only for simple parallel running loops.

  More complex loops (producer/consumer and similar) with the more complex data relationship ships require more valiant approaches such as queues, declaring events or user.

  My 5 cents only,

  Norbert

• Stopping at two while loops, running with queuing

  Hi all

  I'm using labview 8.2.

  I have two while loops in my code (called the main loop and the other average loop - seen on the screenshot file).  I just want to stop both the while loop at the same time (it's ok it the average loop takes a bit longer).  I use global variables to stop (as I have tried the local one, but I don't think that LabView sees in the middle of the subroutine).

  Please give me some suggestions on this.

  Is attached a screenshot and my labview code

  Using a ' functional global' is almost identical with a "global" variable Indeed, before the existence of "global variables", a functional overall, it is how people have this feature.

  The usual way to stop a loop containing a "wait for queue ' is to destroy the queue and use the error on the terminal of the 'expectation of queue' directly in the terminal of the judgment. In this way, you don't have to queue up some kind of end the command to stop it.

  Add a queue to destroy after the stops 'main while loop. Delete the global variable and the error from the stop "waiting in the queue" in the loop "average" it is wire terminal.

  General advice, always try to avoid using local and global variables.

• What is READ the array returned by the DAQmx meter? How can I know the two functions DAQmx READ data stream in the same WHILE loop?

  I have a question about the order of execution.  In the WHILE loop, I have two things to measure, period and tension using the DAQmx READ functions for voltage and the meter.  In the end, I want to collect these data as points almost simultaneously as possible, as a pair and then send them together to another piece of code (not shown here) which them will result in some sort of command for an engine.  It would be run, and then I want to perceive the tension and the period at a time later and do the same thing.

  (1.) I'm a little confused on what the meter of the READ function is back because it's a table.  What is a picture of?  I thought that it was up to the value of the individual periods between rising edges.  The output of the counter 1 DBL d's a table. How many elements in this table, and what determines the size of this table?  Are the elements of the array the individual delays between the edges?  How many values are stored in the array by executing?   We take the AVERAGE of the last 15 items, but do not know if we are throwing some of the data or what.  How to understand the composition of this painting?  How can I change the composition of this painting?  Is it possible to measure only one period at a time, for example the time between TWO edges?

  2.) Will this WHILE loop execute as it gathers tension and a "period table ' (remains to be understood by me) by TIME running in a loop?  In particular, we want that the value of the tension associated with the value of the AVERAGE of the period "array", so we can use two data items to create orders of next control every time that the two values are reported.  The structure for the delivery of vi will be attached data in pairs like this?  I understand that one of the READING functions run not before the other function of READING in the WHILE loop.  I want that the period "means" and "strain (Volt) collected at the same pace. This vi will he?

  Thank you

  Dave

  Hi David,

  I suggest including the DAQmx Start Task function. If it does not start before the loop, it starts the loop and work very well, but it is not as fast and efficient. In the model of task status, task wiill go to run the checked each iteration of the loop and then back the time checked running when it restarts.

  The status of the task model: http://zone.ni.com/reference/en-XX/help/370466V-01/mxcncpts/taskstatemodel/

  Kind regards

  Jason D

  Technical sales engineer

  National Instruments

• problems of operation of two while loops in a VI

  Hi forum,

  I am developing a project for the acquisition of data continuously for two types of signals (voltage and temperature), each consisting of 20 channels. The sampling frequency is different so I used two call loops of different period to take account of the sampling frequency. It is within the VI that is deployed to the target device. On the host VI, I have two loops while put each containing a VI write_to_measurement express so I can connect the data to two different filepaths. However when I run the program, that a signal is registered correctly while the signal remains would have only one row of data. Looks like one of the while loop is only on the iteration while the other is running smoothly. This is an example of the famine of memory? How can I solve this problem! Any help greatly appreciated! Thank you!

  Vincent

  What asked Fan Ravens is why do you use static variable to stop the loop?  You do something remotely?  Simply use a local variable in your second while loop to stop him.  You need to change the action of the button stop, but that would be the way to do it.  Stop buttons are perfect for debugging and development, but generally I will use one other mechanism to stop the program runs outside the environment of LV.

• stop another WHILE loop

  I have two while loops running independently.

  The first has a Structure of the event that controls the STOP button for a user by clicking.

  The second series a bed to a port.

  When I get an error messages entering the serial port, I want to provoke the other WHILE loop stop.

  What is the best way to do it?

  Connect a case structure wire to the error and write to a signaling value property of the button stop in the case of error.

• Stop the multiple while loops in the acquisition of Vision

  Hi, I want to close multiple while loops with a STOP. I use the software for the Acquisition of the Vision for the recording of multiple cameras and I would like to finish this record from all cameras simultaneously. I don't know how to do this since I am knew to LABView. I would add my VI here and maybe someone can help me.  Thank you!

  A local variable should be sufficient for your application. Read the following article:

  Parallel stop, while loops in LabVIEW with a stop switch

• Stop a while loop with outdoor table

  Hello

  I have a problem to stop the execution of a vi that uses a while loop and outside a table with two values of time intervals. I would like to stop the VI when the different values of the array are passed. I have attached here the code if you want to help me please, thank you in advance.

  
  

• While loop, wait for the function and the stop button!

  Hello

  I have a while loop and a stop button. Inside my While loop - I have a 'Wait (x ms)' function. If I press the stop button, it does not block the program immediately, he expects ms x then stops the program. How can I get rid of this?

  Thanks in advance for the help!