Timed loop first iteration to fast

Similar Questions

• "timing" on the first iteration of bad

  Hi people!

  I have a problem with a timer, which gives me a wrong result (only) on the first iteration (see code below).  This test code is assumed to measure time, the loop should iterate x times.

  I expect to get always the same time (i.e. difference  ('period' = 10 (msec) if the settings used in the screenshot) but in fact, the results of the first iteration allways in a smaller number.

  but each iteration after the first gives a good result.

  Thanks a lot for your help in advance!

  Luke

  As I said, at the first iteration, the code that runs to check the time that happens in parallel with the code that makes the calculation of time difference.  In fact, the error in your time will appear in the nth iteration when the differences of time N times, but you have run only waiting for N - 1.  Nth waiting happens in parallel (so after) the calculation of the umpteenth time.

  Next time around you will not see the problem because the nth wait will have been held prior to the iteration n + 1.

  You need to set up a dependency of data stream (possibly a mere 2 framed flat sequence) in the loop so that the calculations occur after the wait function.

• First iteration of a loop problem

  I'm having a problem with the first iteration of a while loop. I want to save all the data a data acquisition over a period of time. In order to keep the unique 'small' file, I'm doing a VI that produce a new file every 10 min. about. But the first file I want to do is not due to the following problem:

  The first time I use the DaqMX read in the loop, it returns a blank. Why does do that?

  I'm not entirely sure why, but I just set the number of samples to a specific value so that you do not need the function of Ms. wait 100 in the loop.

  Tone

• URGENT::opening multiple files - i have 3 files in my directory... When I run the code I can open a file and read it... but the while loop get blocked after the first iteration... can someone me help or give some indications

  bbmChatDB of public database;

  public static FileConnection fconnRead = null;
  public static String fileReadData = "";
  public static InputStream is = null;
  data Byte [] = null;
  DataInputStream is = null;

  Here is my code...

  I have 3 files in my directory... When I run the code I can open a file and read it... but the while loop get blocked after the first iteration... can someone me help or give some indications

  try {}

  FileConnection fc = Connector.open("file:///store/home/user/documents/BSM/") (FileConnection); "

  If (fc.exists ()) {}

  Enumeration e = fc.list ();

  While (e.hasMoreElements ()) {}

  System.out.println ("files are:" + (String) e.nextElement ());

  play this file
  StringBuffer stringBuff = new StringBuffer();
  try {}
  System.out.println ("opening file")-;
  System.out.println ("file name is:" + (String) e.nextElement ());
  fconnRead = Connector.open("file:///store/home/user/documents/BSM/(String)e.nextElement(),Connector.READ_WRITE) (FileConnection);
  System.out.println ("data length")-;
  If (fconnRead.exists ()) {}
  is = fconnRead.openDataInputStream ();
  data = IOUtilities.streamToBytes (is);
  Ddd = new String string (data);
  fileReadData = ddd.toString ();
  System.out.println ("length of data:" + fileReadData.length ());
  System.out.println ("read data :" + fileReadData);

  }

  } catch (IOException ee) {}
  ee.printStackTrace ();
  System.out.println ("Exception in the read data :")
  + ee.getMessage ());
  }

  }
  }

  } catch (IOException e) {}

  e.printStackTrace ();
  }

  {Finally

  try {}
  If (is! = null) {}
  is. Close();
  }
  System.out.println ("is closed...");
  } catch (IOException e1) {}

  E1. PrintStackTrace();
  }

  If (fconnRead! = null) {}
  try {}
  fconnRead.close ();
  } catch (Exception e) {}
  System.out.println (try ());
  }

  }

  }

  You can recode this treatment so that it uses only:

  e.nextElement ())

  Once a loop iteration.

  Directly at the start saying something like:

  String fileName = e.nextElement ());

  and use fileName everywhere in your loop.

  Also be aware that printStackTrace() will do nothing in your situation, it only works if you catch Throwable.  So make sure you something output all your catches exception and also have a catch (Throwable t) to catch the things you miss, as follows:

  {} catch (Throwable t)

  t.printStackTrace ();

  System.out.println ("Eception exception:" + t.toString ());

  }

  I think your code is thrown an exception and you don't see it.

• passing the value and to timed loop

  Hello everyone,

  I'm working on a VI that consists of a timed loop which takes values in a file every 6 ms and writes it to an output file. Inside this timed loop, there is also a MATLAB block that calculates a parameter based on the value. based on this parameter, that a marker is set to 0 or 1 (planned) to operate as a Boolean marker.

  The problem arises when the marker is set to 1. I need an additional structure any that waits five seconds (without stopping the timed loop iterations) and a 'stop' button is not pressed an additional string is placed in the output file. I wish for the marker to get back to 0 if you press the 'stop' button and not string to put in the file.

  The main problem seems to be the use of a structure outside the timed loop. I can't have a while loop or any structure that waits 5 seconds inside the timed loop. And if I let him out he does not have the value of the marker second structure during execution of the timed loop.

  + Any ideas on what the structure to be used during the 5 seconds Timeout? (I tried a while loop)
  + Use a local or global variable for the marker? (I tried briefly, but as a local variable, I couldn't choose a variable defined in the MATLAB block, and I don't understand global variables in LabVIEW)

  I enclose a simplified version of the VI as well as a sample input file in case it can help visualize.

  Thank you
  DAVA

  So far, there are a few problems with your solution, but first of all, I will try to help answer your original question.

  You are right that you can't have a structure inside the timed loop which waits five seconds without blocking execution of the timed for the same period. You are also right that you cannot simply communicate through cables to an external structure. If you exit a loop of wire in the other, which creates a dependency of data flow, which means that the data loop cannot run at all until another loop ends its execution entirely and send data.

  You have two options:

  • Don't actually use a wait function to determine if the 5 seconds elapsed. Use the Express VI of time elapsed (search the palette). He just guard track of how much time has passed since the last reset. It does not wait. If you are safe to use inside your loop timed in a case that is triggered when the marker value becomes 1. Also check the Boolean command in this case Structure to decide if you should output the data in the file.
  • Use an outer loop as in the example you posted, but use screws of the range of synchronization to send data between the parallel loop. Consider a queue.

  But overall, I don't think there is much chance of this work very well. No way, the Matlab Script node running fast enough to run at a time of 6ms. Also no way it works in a deterministic way at all. He needs to communicate with an external program, so its execution time is really unlimited.

• Is there a way to immediately interrupt a timed loop

  Writing a program that, when completed, im could run for a very long time. But I need a timed loop to run every 60 seconds. Option two, I came with are the following

  1 timed loop running every minute

  2 timed loop execution of every second, but treats the content of every minute.

  First way means that I can not stop the loop until the end of the period (more desirable than the 2nd option), the second option is based on the ability to determine when a minute until is based on a rate of iteration 1 Hz, but from what I read, the iteration count will eventually get its max value and simply hold its value the loop continues to run (that's why I lose my logic for the execution of content)

  I really hope, there is a way to make an immediate abandonment of a timed loop, but I'm not finding a way, lol

  

  If the registrant receives an error notification, it passes this error to the error node right over the untimed loop side.  In the contrary case the notifier expires and passes the node error when you want to iterate

• Having a strange action case structure on a timed loop.

  A resolved question yesterday, lead to a new problem. In this VI, I have a timer that triggers an external meter. The counter "counts" from 1 to 24, each with an action at a given time. However, once I got the timer and counter work, I found that the Boolean trigger remained on the hour enitre, and my action was repeated several times instead of only one. So, I changed the counter count 0.1 each interval, rather than 1.0, thinking that it would only allow my State business to operate for a shorter window. However, when I run the VI, the case of the State are active in the meantime, not at the interval. For example, cases of stae 2 is active between 1.5-2.5 iteration and iteration throguh 2.5 3.5 State case 3 is active. Can anyone suggest how to get either 1) better display resolution on the evidence of the State of th or 2) another way to get the Boolean value for just a few seconds?

  Thank you, Lynn.  Yep, I tried that (at least the half of it.)  I opened it in my first version, which is being 8.5.1.  I don't think to check in the dialog changes not saved, however.  I feel kind of sheepish having never tried that before.

  Well, here is my interpretation of what was asked for... I had to make a few assumptions, namely that the 'timed loop' refers to the while loop that runs at a defined interval, and that "triggers" are just the Boolean flags.

  I hope that this at least partially answered questions?

  Jim

• LabVIEW timed loop

  How can I set up a timed loop to run at the entry, rather than waiting for the first time in delta?

  If my delta time is 10 seconds, I get my first run after 10 seconds. I would like to run the loop when he entered at the start (0 seconds) then wait every 10 seconds after that.

  Thank you.

  The first iteration of a loop, a loop's iteration 0.  This will not change to the 1 iteration until the next iteration began.  It is the expected behavior.  Whatever it is inside the loop will run immediately but the iteration count increments until the next iteration begins.

• LabVIEW FPGA while loop (first call? (VI) question

  Hi gentlemen!

  I am creating a LabVIEW FPGA VI appearing in a WHILE loop. He has a first call? VI in which, in the first occurrence of the loop, a variable must be initialized to some value. However, when I incorporate the VI in the FPGA, it would seem that the first call? VI has not been called. I also tried this implementation through registers at offset where the registry is initialized outside of the WHILE loop. However, the result is always the same. May I ask how the LabVIEW FPGA functions when it comes to everything IN a loop? Thank you very much!

  For some reason that I don't me remember not I avoided the use of FPGA FirstCall and instead, I use a change sign boolean, son of genuine in the terminal, on the left and a fake in the while loop to the right Terminal. As a result, you get a true for the first iteration only, in exactly in the same way that the function of FirstCall. It could even use fewer resources on the FPGA?

• Timed-loop frequency of 1 MHz

  I have two codes for my NI9024 cRIO; an FPGA and a side side of RT.

  In my RT code, I use a frequency of 1 MHz for my timed loop.

  Just wanted to check if I should consider certain things important when using this frequency or not.

  I mean, is there a particular point or referring to the fact that I had noticed.

  Is there any limitation, future problem or question?

  Just to be careful.

  

  I think that the point that you are missing, it is that it is never necessary to update a graph 1000 times per second!  operators just can't see that fast!  So, unless you save the data on a disk, you can use a much slower pace of update.  You can indeed, be limitation in this loop timed by your actual acquisition rate (timeout is 5 seconds - what is the sampling frequency of the FIFO?)

  If the buffer is full or reduce the sampling frequency of the FPGA (a million points per second is really much more that a human eye can process) or increase the number of samples by reading.

• How to force a new period of a timed loop?

  Hello.

  Here my question:

  I need to modify programmatically the period of a timed loop. This isn't a problem but:

  I have to wait until the next loop to present new period value. For example if my previous period was 20 minutes, now I have to wait 20 minutes in order to submit a new period.

  This beacause the code to change the period should be inside the timed loop itself. You can see what I mean in the picture as an attachment.

  

  The Subvi Gets the new period of a console operator. It will run until the end of the period previously configured.

  My question is: is it possible to force the timed loop to get the new value without waiting for the execution of the previous period?

  Thank you

  FPIA

  Hi fpia.

  Sometimes, it would be more useful to 1200 seconds instead of 20 minutes

  It was suggested many times before: rather than wait for a long time with just a single call to a wait function you should divide this amount of time into smaller pieces!

  -Why do not use you a period of time for example 5 and only count the iterations to know when 20 minutes are more?

  -Why don't you use the function "Time" to know when to exceed the 20 minutes?

• Module speed FPGA, speed controller and timed loop speed

  Hello.

  I'm developing an application to acquire an analog signal at 800kS/s. Budget does not seem to be enough buy material excess spec. So I have to be very very accurate on all components. I had a look on the site and selected the following materials.

  9221 8 module capable analog channel on 800kS/s sampling. I don't know if this sampling rate indicated in the specification of the module means that it can acquire up to 800kS/s or is the device samples ADC sampling rate to which the machine don't maybe not to the criteria of Nyquist and the module can perform sampling to 1.6MS / s is necessary which I think is not available?

  9012-400 MHZ controller controller. If I put a while loop inside a VI under the RT target, it runs at 400 MHZ by default provided there is no code inside? Is so I could definitely use loop time express vi for sampling at the required level.

  What of the timed loop? I just developed a project of RT and added vi under the RT target. The timed loop default clock frequency is 1 kHz and I can't select more than 1 MHz?

  9112 chassis. Default clock 40 MHz. same rate issue which concerns the 9012 above controller.

  Kind regards

  Hi AustinCann

  If you need to acquire 800 kech. / s, then the module module-9221 will be able to do this, if you are using only 1 channel, that is.  The module using a global sample, therefore the maximum rate will be distributed on channels that you use.

  If, however, you have to detect the frequency of > 400 then you would need a higher sampling rate to detect these, as you mentioned.

  The controller processor runs at 400 MHz, even though the loops in your code will not run at this pace.  On the target in real time, you can use a timed sources of clock - usually 1 kHz to 1 MHz - and set the period in terms of the chosen clock.  If you need faster line rates, you can still code directly on the FPGA.  The CompactRIO Developers Guide is a comprensive document and deals with most of the concepts of RT and FPGA.

  The best course of action would be to contact your local office, because they have all the resources necessary for the specification of your system.

• 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.

• loop for iterator goes from 0 to random number?

  Hi all

  I have a loop with a tunnle auto-indexé coming out of it.  The for loop is defined to run 240 times (4 x / sec.), then the table when he went from the loop is on average and data is played from there on out.

  It works fine except for the first round which is shake more data on the entire line.  It will run across the 20ish seconds seconds to 50ish.

  If I put a flag on the index it will increase from 0 to a number between 7 and 160 randomly as soon as the program starts.  From there on, after the first iteration it fires every minute.  However the timestamps on all data are not at the minute, for example. 01:00, 02:00, 03:00, etc.  They are at a different interval, for example: 01:16, 02:16, 03:16 etc.

  Why would he do that?

  My guess is that the output array has some kind of memory of the previous races and is the first notches n fill with data stored and accessible to the general public starting the iterator to the next index, and continues from there.

  Is there a way to reset the data stored in the tunnle?  I do not use a shift register.

  If I change a shift register and try to transmit data to the output function of summons since the shift register, there is an error on the output and gives me a bad connection.

  If I change a shift register and try to transmit data to the service of summons since the input shift register, it will work but continues to count arbitrary point.

  If I change a shift register and try to intitialize the table by connecting a constant to 0, it continues to count arbitrary point.

  Any help would be greatly appreciated.

  Thank you.

  What is the format of the data being sent?  Should I use jump as end of line character? It sends all the time?

  If she is using jump for line termination, your configuration is correct (well that count = 50 byte may not be the best). You should not use bytes on Port when the characters of endpoints are enabled. With the characters of endpoint read VISA sets the calendar to match the received data.

  With the default settings of the configuration, it will take about 50 ms to 50 characters. If messages are less than 50 characters, the delay will be less. Two examples: 1. device sends continuous and date never has a line break character. Read return 50 characters around every 50 m 2. Message consists of 8 data characters more line break. The device stops between messages, then send 4 messages per second. Read return 8 characters 4 times per second.

  My guess is that your device sends permanently and that something else in the program allows some data accumulate occasionally, so that at the start of this VI a batch of messages are in the buffer and treated quickly enough that you do not see the loop counter increment.

  Lynn

• What happens if my computer cannot process a pretty quickly timed loop?

  If I created a loop timed, but required that more important than my computer treatment is able to do before the next iteration the tasks within the loop, what happens?  It gives me an error or I miss loops?  In the end, I need to know how can I know if the problem occurs.

  Please see the setting the Mode of a section of the loop timed in the following document.

  http://zone.NI.com/reference/en-XX/help/371361F-01/lvconcepts/configuring_the_labview_timed_loop/

  The left consider the following section describes the information that you can access on the previous iteration of the timed loop.

  http://zone.NI.com/reference/en-XX/help/371361F-01/Glang/timed_loop/