While loop inside a timed loop

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• Timed loop versus While loop

  Most of the machine control software I design have the following structure:

  1. There's a HAND that takes place inside a TIMED LOOP with synchronization of 50ms and priority of 100. His only job is to read / write data from / to DAQMx IO cards.

  2. the MAJOR can call several SUBs based on the choice of the user, and once a submarine is called FP MAIN is closed and the FP SUB opens. All submarines have a States Queued Machine running within a TIMED LOOP with 50ms timing but with priority to 50.

  3. data transfer between HAND / SUB is through function globals - there are many of them based on past data.

  4. all woks fine so far. No need to any RTOS. and platform of WIN7 is alomost standard. I even ran with a timing of 20ms without anything crashing...

  Problem: When there are a lot of file i/o operations in a SUB partciluar, then I have the chance to see several missed iterations. Perhaps the TIMED LOOP is hogging resources.

  What I want to do: convert both TIMED in asnd SUB HAND loops simple while loops.  But I am concerned by the priority - since the MAIN interacts with HW there priority. But with LOOP WHILE how can I ensure this?

  Or is there any replacement / effective way of doing what I do now?

  Rama wrote:

  .... FGV should be thrown out the window...

  Well used for a while, based on many articles in the KB. One of them is locked... and it does not represent the engine of the Action or of the FGV as a villain to avoid.

  The driving force is one of the largest buildings in LabVIEW.  The FGV who does nothing but Get and Set (or writing and reading) is useless and a waste of resources.  Why?  It does nothing to fix possible race conditions (does not protect critical sections) and it is much slower than just using a global variable.  See this example I put in place to see what I mean: an overview of the race Conditions.

  Rama wrote:

  So in the sample that I had attached, what do you think would happen if I just replaced the two loops with the SAME timed in MAIN and SUB wait value ms. is there a work order then?

  When things are at the same time, there is no such thing as the order of execution.  But as I said, it seems that your loop is quite slow, so it's something I would not worry.  Just make sure that you do not have a loop that uses all the CPU.

• convert loop timed to normal while loop

  How convert a while loop time normal while loop with exact same properties and performance?

  I have donot need to worry about the exact date. But it takes the timed loop time will be run similar to loop.

  And also, is there any issue encountered when we use Timed loop? problems such as that crashing exe?

  Hello

  1 kHz is the used base clock. Then, you decide to use 10 as period (dt) which is 10 ms.

  The clock is selectable in real-time systems, you can use the 1 MHz clock, giving resolution µs

  But for your needs, using 1 kHz clock with dt = 10 and using a ms of waiting with 10 connected to it is exactly the same.

• How to have a while loop inside a structure of matter?

  Hi all

  I would like to know how to control a while loop by using the structure of the case? I would like the person to check if the object has is in its original position or not.

  If this is the case, go...

  The object must then do its job, as mentioned in the while loop... as up and down 10blocks...

  Later, when she returns to its original position, the entire process must stop...

  I checked the forums on this http://forums.ni.com/t5/LabVIEW/How-to-stop-while-loops-inside-a-case-structure/m-p/591259

  It is the closest, I can have... but can someone tell me how to program for this? How logic should be?

  
  

• Sequence structure flat inside the timed loop and execution order

  I have some problems trying to implement a flat sequence structure when you use a loop timed on a target of cRio VI

  I tried with or without the while loop around the structure of sequence flat, and I also tried to replace the 'Non-deterministic loop' with a timed loop

  The problem is that the program seems to run only once, then get stuck somewhere

  I am writing a program that performs the following operations as soon as possible:
  1. read the Pos_MC of entry on the FPGA
  2 send the value of Pos_MC to the VI target (on cRio CPU)
  3. calculate a value of output based on Pos_MC with a PID block ("exit PID')
  4. send 'PID output' to the FPGA
  5 write "PID output" analog output "MOOG".

  In addition, I want the program to return the measured value "Pos_MC" to a host VI for the recording of data

  So that the output of PID is calculated and sent to the FPGA as quickly as possible, I placed a flat sequence structure to ensure that it happens before you send the output to the nondeterministic loop for recording data

  Also, I want the digital input 'Stop' to be able to stop the loop deterministic (the timed loop)

  I read much more entries than that and the help of several PID and exit, but I rewrote the code for a single entry and exit to make it easier to illustrate

  Screenshot of the code is shown in 'target code.png' and 'fpga code.png.

  The VI themselves are attached in the next post (cannot attach files of more than 3)

  Question 1:
  Any advice on how to get this race? Thank you!

  Question 2:
  Is also my correct understanding in that, using this structure, each 0.9ms (fpga loop time) comes the following:
  1. the input ("Pos_MOOG") is read on the fpga
  2. the production of PID is calculated on the cRio with some delay to computation (for example 0.1ms)
  3. the output of PID is then written for analog output "MOOG" in all about 0, 1 - 0.2ms
  4. the FPGA program then waits until 0.9ms spent and repeat the process

  As opposed to the next pass whenever performing a loop is started on the FPGA:

  1. the FPGA reads the input and written on the output (the output of the execution of the previous loop PID)

  2. then the entry is sent the cRio, PID output is calculated and sent to the FPGA

  3. the new release of PID is maintained until the next time through the loop

  Thank you!

  PHG wrote:

  Thanks for the input guys, any advice as to how I could get the feature in scenario 1?

  I still say that the best route is just putting all the logic of the control in the FPGA.

  Other alternatives include 1) the use of DMA FIFO sedn data back or 2) use interruptions so that the FPGA code can not read the output level until the RT.

  DMA FIFOs are usually very limited, and I would not use them in this situation since I belive said it this code to do for the many outputs.

• dispplaying data on the graph of waveform inside/outside while loop

  I create a vi using the random number generator, entering the number in the function(express>>arithmateic>>maths>>trig>>sine) fishing and connect the output of the function sine waveforms. Table of waveform show no problem. If I replace the with graphic waveform table, I get an error that the source type is differenct type of sink. I then put waveform chart outside loop everything hoping that tunnel would act as a table, but still I get the same error. I then put build table palette between all border and loop waveform graph which is placed outside the while loop. I get no error, but no data is displayed on the graph of a waveform. Theoretically, if I press stop I would see a distorted sine wave on the waveform graph, but this doesn't seem to be the case. I am wondering how to view data on the graph of a waveform in such cases!

  Thank you in advance for reading and help!

  See you soon

  First of all, you can take a part of the basis of LabVIEW tutorials.

  Since you need to work with a chart and it is the preferred method to display data point by point, I don't know why you try to use a chart. In any case, you cannot use all simply a table of generation because that would be just the result of the last iteration and your graph indicates it is a single point. If you activate autoindexing, then you get all the values, but not before the end of the loop. If you were to use a shift register and the build dashboard, you might place the graphic inside the loop, but then you would face performance issues that the table would grow uncontrollably.

• stop the loop inside while loop

  Hi all

  Is there a way to stop a loop within a while loop? Error-free program will stop running when you press the stop button, but I want to while loop continues to run in and only for the loop stops when the condition is met.

  Thank you!

  Hi TayAus 1.

  If you want to run the execution once? Maybe something like below? The code inside the structure of events can only run when the event source is triggered. For example, the code in the digital works only when it detects a change in the numerical value (just an example).

  

  When the button is selected, it should raise the event to stop as shown below:

  

  If you want to create the event source, create the structure of the event > right-click on the frame and select edit events dealing with this... > This should open Edit events.

  The example below is that I put the event source for the change in the value of x and x 2.

  

  So when x or x 2 value is changed, executes the code in the sous-schema event shown below.

  

  Warm greetings,

  Lennard.C

• How to run a while loop continuously without iterate loop inside the fi, a condition is met

  I enclose a VI that once the answer 28 comes the loop must stop and loop should continue an iteration. Can you show me a way for her

  You can stop the loop when a certain condition occurs: http://zone.ni.com/reference/en-XX/help/371361H-01/lvhowto/add_cond_to_for_loop/

  Add a register to offset for the while loop and to implement the feature as below:

  

• How to make a graphic inside a while loop to maintain the previous values

  At first I tried to use a the VI Express XY graphics to create a track of points.  However, the chart is a trace linear between the first point in the new line and the last point of the previous line.  It then creates the new line as you wish.

  I tried to use a loop with group a cluster for the chart, but the chart resets the plot at each iteration (as expected) and I can't find a way to maintain the previous data.  I tried using shift registers, but was unable to find a way to do it, and I tried also the cluster of a painting company, but can not find a way to make the cluster to a 1 d of a cluster of 2 elements array.

  One option is to have is to find a way to maintain the previous data, but the preferred option is to create a new path to each iteration to see the color change for each new parcel.

  I take stabbed it because I don't know exactly what you want. But I think that's what I've shown here. You must use a shift on your outside register while loop, as I showed. Your image where you tried to use a shift register shows a misunderstanding of the shift registers and how well they work, then I'd take a peek at these tutorials.

  

• While loops inside while loops, how to stop?

  Hey, I'm confused with a simpler question to multiple while loops. My goal: stop or pylone2, just jump out of the small loop and stay in the big one. and if I click on stop 3. the entire program would cease... How can I do this? The following script does not at all... Thanks in advance!

  Yes you are completely right Mike... now, I solved the problem with another structure of the event and the Boolean variable local... Thank you very much!

• How to add the unique element (inside the while loop) to itself

  I have only digital output element that is in the while loop. Its value changes in each time the loop iteration. If lets say I want to adds the values of the ten first in iterations of the loop of this variable.  How can I do that.

  See attach image for more precision.

  Thank you

  JK

  

  Hi Joseph,.

  THINK THE STREAM!

  As the values are stored in the son and the shift registers (and NOT in any kind of variables), you must use these fundamentals of LabVIEW:

  

• Structure of the event inside while loop

  I'm still fairly new to Labview and this may seem a simple question.  I'm doing a Subvi to display, edit, and create configuration files.  I use a ListBox to list all sections of a config file and structure of the event to update the values in each section, when they are clicked.  The problem is that the structure of the event seems to be a break the while loop so that the buttons do not work until the event has executed.  What I would like is the while loop to run continuously and the event to run only when I click in the listbox control.  I hope this makes sense.  There is a peak in the diagram below. Thank you

  There are a number of issues with your code that could cause problems:

  1. You must use the FP. Open method to open the front panel of a VI and of the public Service. Close method to close. I don't remember exactly the problem, but starting with the 7 worm nor indicated that these methods were the preferred way to perform these tasks.
  2. Based on what seems to be the code, the event for the control of Presets of wood should be a change the value - not a mouse down event. After changing the type of event, use the event data NewVal to drive the indexer table index entry.
  3. The buttons Ok and cancel them should be handled in their own events to change the value. The value change event Cancel would exit the loop, while passing the output error (which indicates that cancel was pressed) and default values for the other 4 outputs. The change of the value Ok event would leave the loop by passing the values that the operator had concluded the 4 controls on the front panel.
  4. An event of timeout with a very short time (1 msec) would stop loop if an error has occurred, or the output of the gate AND is set to true.
  5. The wait function is not necessary, as is the case outside the loop structure.

  Mike...

• void / vi... read vi inside while loop

  Hello

  I'm new to Labview... My main Vi keep reading data from serial port and parks (in words) in a table (put all in a while loop)...

  The table is also inner while loop... Now I still want to analyze this (element by elemnt) table and create an another VI who takes this array running as input... so the new VI should simply have this table entry... but the problem is that I can't see the data running in new vi... .any suggestions... ??

  ebuckbuck wrote:

  Thanks Apok...

  I'm not sure hoiw reference books here as when I create refernce of table VI main (24 sep... (VI)... it does not produce yet of any substance in following VI (who called)... Attached are my two files... .and I just want my main VI as for the output as array2 Terminal...

  Thank you very much

  ebuckbuck

  in this example, we want to move an indicator (main.vi) digital of the second loop (sub.vi)...

  

• How to increase code efficiency in a while loop (using PXI5105 for sampling outside signal digitalizer)

  Theoretically, we want the PXI-5105 (digitizer) have 302 record with each record has a 1260 sample (the save operation is inside a while loop) in approximately 30ms, however we have found that for each period (30ms), the PXI5105 only perform about 10 records. It is so wired. I wonder if the operations inside the while loop consume more time (for example 3MS), so that he cannot have 302 records even the PXI-5105 have 60 M/s speed of sampling. Is it true, you can find my labview code and if possible can you give me some suggestion in the most short time of operation of the loop.

  

  Please find attached labview code.

  Hi g_l_g_s,

  The digitizer PXI-5105 acquires data at the speed that you specify and stores the data in its memory embedded (up to 512 MB). The data is then sent to your computer when the Multi Fetch Cluster.vi is called. In VI that you posted, you are only fetch record during each while the loop iteration. If you want to retrieve 302 records you will need to specify 302 files in the horizontal Timing.vi to configure. For more information about scanners, you might find the DevZone, hereuseful.

  To determine the amount of time it takes for each while the loop iteration, you can consider using the structure of code in the example comparison community calendar, which is located here.

• While loop within a while loop

  Just a general question, is a timed, while that while loop the loop inside of a timed bad design practice?

  Any feed back on why it shouldn't be done is appreciated.

  mhaque

  Yes, it's very bad design.

  The outer timed loop cannot complete its iteration unless the timed inner loop ends. This means that its target of time cannot be carried out unless it is guaranteed to be much longer than the total time of the execution of the inner loop. Too late!

  What are you actually trying to do with all this?