Producer consumer timing

Back again
Thought I was getting somewhere now I am at another brick wall.
Bit of background:
I have a producer consumer set up. In the producer loop there are 2 DAQmx read VI's reading from a Pressure task and a Temperature task. These are multiple channels, 1 sample, outputtng a 1D wave form. This loop is set to run every 20ms. The two tasks were created using DAQmx Create Channel VI's and DAQmx Start Task VI's. The producer loop feeds a display on the front panel with the sensor values and this hopefully is refreshed at the 50Hz I have asked for. Secondly the loop bundles up the waveforms and puts them in a queue where they are picked up for logging by the consumer loop. In the consumer loop I have a wait 1000ms timer and a Write to Measurment File Express VI to do the logging. This is supposed to log at 1 per second.
The queue is set to enqueue at opposite end, and the max queue length is set to 1. I.E. I only want to log the value at that specific second, but I want to show the data on the front panel at 50 times a second.
Now heres my problems:
1) I replaced the DAQmx Create channel's with a MAX project task wired into my DAQmx Start Task VI. As expected the thing picks up and displays the sensor values as it did before. However there is now a problem logging. Before when I had the DAQmx Create Channel, the logging recorded my values correctly at 1 second intervals. The time stamp in the X column went up by 1 second for each set of results. But now, with the MAX project task (needed because of custom scales and differing min/max values for different sensors), The logging still seems to happen at 1 per second, but the time stamp intervals are the same as the sampling rate set in the task!!! (ie at 50Hz the time stamp goes up 20ms for each result even though the results are being recorded at 1 per second)
2) The timing just seems out of whack.
I keep getting errors that the requested data no longer exists, that it was there but then was over written. Increasing the buffer size or sampling rate is supposed to remedy this... but what sampling rate? the rate set in the task? or the loop iteration speed? I dont understand.
Secondly, despite telling my consumer loop to wait one second between picking up stuff out of the queue to log, it seems to be going round nearly the same pace as the producer loop. To top this off the producer isnt going round at the speed I asked it too either! I put indicators on the loop counters to see this. they are going round at maybe 2Hz.
I have included my VI's
What am I doing wrong, its really bugging the crap out of me!
Attachments:
EngineMon.zip ‏90 KB

The reason you would use get time and date in seconds to to ensure that you log every second. If you use the 1 second wait then you do not take into account the exicution time of your loop. If you add more to the loop in the future than you will see that you do not log every second as you thought. If you loop took 500ms to exicute and you have the 1000ms wait then the actual excution time for recoding to file is 1.5 seconds not 1000ms as you desired. The way I did it will always give you one second unless you exicution time for your loop exceeds one second.''
I did make one change to the vi. I shoulod have put the write in the true false case so that the write only happens when the 1 second has expired.
Tim
Johnson Controls
Holland Michigan
Attachments:
VDU3.vi ‏59 KB

Similar Messages

Producer/consumer architecture - timing

Hello.
I have some question about producer consumer pattern.
People say that consumer shound NOT add elements into producer queue. Lets say that some states in in consumer need to stay active for eg 5 minutes. We also should be able to pause/resume state execution and exit program in any time.
I ve used functional global timer but consumer adds elements into queue and this should be avoided.
How to solve timing problem? Some people have written about creating another thread - watchdog or asynchornous calls to vi...
Could someone explain this to me? :

People have consumers add to their own queue all the time. It is usually in a Queued State Machine though. If you have a process that just needs to run for so long, then have the consumer run another while loop until the time is up. It can then process the next item in the queue.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Timed structure for output in producer consumer data acquisition

Hello LabVIEW community,
I have a bit of a problem. I am writing a program that is primarily for data aquisition but has a few control features as well. I need the program to aquire and write several channels of data at a relitively high speed. The program does this fine ( in the top 3 loops fo the program). I need the program to also send a seires of two output signals in response to a particular condition. When a certain channel registers a value of above a specified number, I need an output channel to write an anologue signal for 225 seconds and then a signal of a differnt value to the same channel untill the condition occurs again (not for several hours).
I put this action in a timed structure inside of a case structure. The case structure and timed structure are inside of a second consumer loop. I have no idea if this is ligitimate. This event takes much longer than any of the other loops which run at 1 or 2 seconds. When I exicute the program with "highlight exexutuion" this longer (case/ timed ) loop never executes. I asssume this has to do with the mismatch in time scales of this loop and the other loops in the program. I also didn't really understand the help information on timed structures, so its possible that I just need better/ different inputs to the timed stuctures.
If anyone can see any obvious problem in the code or suggest a better way to do the output function I would really appreciate the help. My code is attached.
Thanks,
Jo

I can't figure out how to fix your code, but I can point out the things I see wrong with it.
1. You are dequeueing elements from the same queue in the same loop. In one you are not taking the element, and in parallel, you are taking an element. I see that in your bottom two loops. Why? That code won't execute until the queue gets two elements in it. And which dequeue gets it first and which gets it second is an arbitrary race condition. So there is no certainly of order (first 4 vs. last 4 currents in the one loop), or which gets kept and which gets discarded (in the other loop.)
2. You are creating and/or clearing DAQ tasks in every loop iteration. Tasks should be created before a loop, used inside the loop (read or write), then cleared once the loop is done. Anything else is wasteful, time consuming, and could lead you to run out of resources.
3. You are using the STOP function which is pretty much like hitting the abort button on the toolbar. No program should ever stop that way. All loops should exit gracefully.
4. You have a data dependncy between your bottom two loops because of the boolean wire running from one to the other. That bottom loop will only run once (if the value is True), or run forever (if the value is false).
5. Use of the dynamic datatype. You are taking waveforms, converting them to a blue wire, then coercing them into another datatype such as just displaying a scalar in an indicator. A lot of unnecessary conversions there.
6. Your thermometer indicators have a digital display you can make visible. Then you won't need the separate numeric indicator to display the value.
7. For loop that runs only 1 time because of the constant wired to the N terminal. Get rid of the For Loop.
8. Check your spelling. The word "Temperatures" on the graph, and one instance of "distillate" is missing an "l".
Until all of these problems are fixed, it is not worth talking about timing of timed structures. Some of these problems were discussed in your other thread. http://forums.ni.com/t5/LabVIEW/producer-consumer-missing-channels/m-p/3159757#M911255 But now it seems like you've made things even more complicated without fixing the basic problems.

Timed Loop in Producer/Consumer Loop

Hello!
I have a producer/consumer loop LabVIEW program setup to allow me to properly capture images that are quite large (8MP) at approximately 14 frames per second (FPS). The program works great when the consumer loop is a 'while loop' (records at 14fps no problem), but I wanted to make it into a timed loop, so that I may vary the FPS as required. An oddity arises when I do this. Anywhere below 12fps, the loop works fine and the data is recorded properly. However, when I bump it up to 13fps, the consumer calculated FPS goes haywire and starts jumping between ~9 and ~13fps (data processing gets bogged?). When I set the required FPS to 14, the loop executes at a steady 7FPS maximum. Is there something I can do to rectify this situation?
I have attached my .VI
Thanks in advance!
Solved!
Go to Solution.
Attachments:
ProcessSplitJPG-FPS.vi ‏100 KB

Palanski,
Are you using LabVIEW Real-Time? Timed loops in a windows OS don't really increase determinism more than a while loop with a wait until next multiple timer. Before you changed the producer consumer loop to include a while loop was the programming running correctly? You may also want to vuse the VI analyizer to see how long things are taking to run. I would leave the producer consumer loop in the traditional set up and change the FPS by controlling the wait timer, after benchmarking your code this should be done the same way as you have it for the timed loop
Sam S
Applications Engineer
National Instruments

X-Scale Timing, Producer Consumer Structure

Good day,
I'm using a Producer consumer structure and I'm enqueueing data every time in a while, almost every 50 minutes, and I want to make a graph with the Amplitud in the Y-Scale and the time in the X-Scale but I cant get right the timing for the graph...
Any ideas about how to keep the initial time as the first value and any next sample with the correct time?
Best regards,
Esteban Gonzalez
P.s. This is what I've got so far.
Attachments:
BlockDiagram.png ‏56 KB
Front Panel.png ‏29 KB

Hello,
My name is David and I am an Applications Engineer at National Instruments UK.
It seems that the problem that you are having is a simple scaling problem with the X-axis. If you follow the following steps it should solve this for you:
Right click the graph and select X Scale >> AutoScale X to disable AutoScaling on the X-axis.
Right click again and select X Scale >> Properties. Go to the Display Format tab in the window that appears.
Ensure that you have the Time (X-axis) selected and select Absolute Time under Type.
Navigate to the Scale tab and adjust the value for Maximum. This is the maximum number of seconds that you want the scale to run for.
Hint: You can also change the sort of clock time that is displayed on the X-axis in the Display Format tab.
I hope this helps.
Regards
David B
Applications Engineer
National Instruments UK

Producer Consumer simultaneous operations at different frequencies

My goal is to do two operations simultaneously.
The desired end result is:
1)      Produce an output signal which oscillates at a specified frequency (1 to 10 hz)(using DIO NI-9403). This signal will cause a solenoid to vibrate at different frequencies.
2)      Monitor voltage on 3 lines in real-time (using analog input NI-9201). This will monitor system response to vibration.
3)      Produce an output signal which oscillates at a different frequency from (1) – producing 1-second HI values 5 seconds apart. This will cause the system to “pulse”; system response will be monitored.
4)      Have a front-panel user interface where: the signals in (2) can be monitored; frequency of (1) can be monitored and changed; and the output on (3) can be monitored and changed.
My efforts so far have been to build a producer-consumer structure. This is my first time using this structure so I may be completely misunderstanding its use. Feel free to correct me if I’m way off target.
The issue I have is the solenoid in the consumer loop (which handles item (1)) is not operating at the desired frequency. It is too slow. I used a 10ms timer for this loop, but instead it is operating about 1 cycle per second.
There may be a much better way to approach this, or maybe my program only needs some minor tweaks. Either way, thanks in advance for your help.
Attachments:
ProdComsLoop Pulser 2-27-14.vi ‏65 KB

Hi BradleyDDC,
It seems from your program that you don't need a producer consumer loop. The only thing you are feeding from one loop to another can be put in one loop, I mean the simulator on button.
The timer does not determine how fast the loop runs in real time. To get more precise timings, we recommend hardware timed operations as opposed to the software timed ones.
Instead of using a digital output signal, you can use a counter output task, here is a knowledgebase, which has an example of what you may want.
Paolo F.
National Instruments
Applications Engineer

Producer/consumer w/ScanEngine issue

All,
I have a large VI implemented with producer/consumer architecture using 10 events and uses conditional disables to select the data acquisition hardware. The application is being developed in LV2009 with FPGA & RT on XP. The application is intended to acquire and control analog signals in a cRIO-9073, but early development is done using LV simulated signals. I can switch back/forth between the different configurations quickly & easily. In the simulation mode, the front panel, controls, events, etc; all behave as one would expect. When the conditional disable is changed to use ScanEngine and cRIO modules, then a very primary control fails to generate an event and does not function. All other controls that can be tested are functional and generate their events. I am at a loss and seeking suggestions on techniques to diagnose & fix the problem. The application behaves as if the 'event structure' for primary control gets corrupted or some size threshold is been exceeded. The whole concept, scanEngine based and simulated data, were functioning several days ago prior to numeruous edits and I can revert back to not using the scan engine and cRIO hardware with simulated data to validate correct function, but that is not the intended final path. At the present time, I am stuck and looking for ideas. All suggestions will be considered and appreciated. The applicatiion is company proprietary and can't be posted. Thanks in advance.

I can definitely understand your confusion, and on the surface it seems like everything should transfer over. However, when using simulated data you won't get errors that can occur once you introduce hardware. Errors can prevent events from occuring, there is also the issue of timing, to see if when using actual hardware, the timing causes issues. As I menationed before, there are a hundred different reasons why it would work with simulated data, but not actual hardware. Please let me know if you need further direction in your troubleshooting.
National Instruments
Applications Engineer

Producer/Consumer Design Pattern + DAQmx + Event Structure

Dear community users,
at the moment I try to implement the Producer/Consumer Design Pattern into my current project. For this purpose I am trying to make a "minimal-example" in which I use the Producer/Consumer Design Pattern for the data acquisition and analysis (display in GraphXY, calculation etc..) process. In the Producer Loop I perform the data readings via DAQmxRead.VI and in the Consumer Loop, in this example only, I display the data in a GraphXY. At the same time I want to control the data acquisition via an Event Structure, for example Start Measurement/Stop Measurement Buttons. To configure the measurement time, for example if the user only wants to measure 150 sec, I use the Time Out Event of the Event Structure. This is a technique which is often used, when data acquisition and Event Structures are used at the same time (Excuse me if this is wrong!). Due to understand the Producer/Consumer Design Pattern I looked up in the Template\Framework of LabVIEW.
In the attachment you will find my "minimal-example", which -sadly-, not working. What should I do ?
Thank you.
Best regards,
tugrul öztürk
Attachments:
daqEngine_PCP.vi ‏35 KB

Your VI will never stop due to the Ok Button that stops the producer loop is read OUTSIDE of the loop. Add an event case for it.
Move the Start and the Ok Button inside of their respective event cases. This will allow the latch to reset when they are read.
Change the Ok Button to a stop button.
Use a Greater Or Equal instead of Equal for the measurement time comparison. What if somebody randomly changes it to 0 on you? Again, you will never stop.
Is the DAQ only supposed to read for "Measurement Time". Right now, it constantly reads. So if you don't use the DAQmx Read, you will get a buffer overflow error. You need to put the DAQmx Start Task inside of the Start event case and then the Stop DAQmx Task inside of the Timeout event case when the measurement time is exceeded. You should also perform the read regardless inside of the Timeout event case.
I HATE telling the consumer loop to stop by destroying the queue. You can look data that way. Instead, send something an empty array. In the consumer, check for an empty array. If it is empty, stop. Destroy the queue only AFTER BOTH LOOPS HAVE COMPLETED.
You should also report your errors in some way. Simple Error Handler at the minimum.
Since you are using Continous Samples, don't limit the buffer. Leave the Samples per Channel unwired on the DAQmx Timing VI.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Progmatically stop vi with producer/consumer architecture

I can't seem to get my VI to fully stop, so that I can go on to do some more things in the program. I am trying to progmatically stop the vi (pictured below), so that I can return to my main gui (not pictured). The main gui just consists of a login, exit test system, and run test. Once the user presses run test, the vi pictured below opens.
I am using a producer/consumer architecture with a state machine. The problem I run into is that when I press the "Main Menu" button, it should close the pictured vi and return to the main gui. I tried using the vi server, and when the user presses the Main Menu button, it fires an event and then it goes to the Stop state in the consumer loop, which opens a reference to the vi's (one for the strip chart vi and another for the gage vi), closes the front panel using an invoke node and then closing the reference. I also tried adding in the abort vi method after the close front panel and it still gave me the same result.
Here is the catch, it does close the vi's, but it does not stop the while loops (producer and consumer), or it stops only one of the loops. I thought of putting in a constant in the event structure for when the Main Menu event is fired, but that will stop the producer loop before the consumer loop reveices the info to go to the stop state, so the consumer loop does not end.
I also tried a "dummy" control that was connected to the comsumer loop Stop terminal (for the while loop), and then progmatically changed the value in the stop case to true and then read that value in the producer loop to, hopefully, stop both loops, but it did not work either.
I am sure that it is something so stuipidly simple that I cant see it right now
Kenny
Kenny
Attachments:
test system.gif ‏252 KB

Hi Kenny,
I think of two solutions to your problem. First, use the message queue to pass the message "stop" or something from producer to consumer or second (and I think, better), use occurrences. I made a little draft how it could work.
You have to pass the occurence- Refnum to both VIs, the producer and the consumer, when the producer finishes execution, then use "Set Occurence".
In the consumer blockdiagram you react on the generated occurrence.
If you set in the VI- properties "Open Frontpanel when called" and "Close if originally..." the VI Frontpanel should disappear itself when execution is stopped.
Hope this helps,
Dave
Message Edited by daveTW on 08-14-2006 04:53 PM
Greets, Dave
Attachments:
occurrence 1.png ‏1 KB
occurrence 2.png ‏5 KB

How to change the transmission rate of data flow in producer/ consumer pattern

Hi All
I am new to labview and trying to design a application to transfer image data in different rates, that means I can change the transfer rate in the transmission process. In fact,I refer to the the Queue Basic.vi to achieve this function by Changing the delay value of dequeue and enqueue.The program is divided into three parts:
The first part is the sender in vc used to split and send image data.Data size is 226kb and each time we send a 1kb packet;
The second is labview rate-change part，use producer/ consumer pattern and queue to transfer data;
The third one is the receiver in vc,receive data in sequence and synthetic images.
The entire transfer process is: image data was sent from the sender to producer loop through DLL, then enqueue--dequeue in consumer loop--DLL--receiver.The sleep time in vc sender is equal to the delay value in producer loop and this makes it look like the data generated as in the loop.
Now this is where my dilemma is：
When transferring data, if the producer loop and consumer loop delay value are equal(both 20ms), I can see image synthesis at a constant speed and no data lose; if I change the consumer loop delay value and make it greater than the producer delay(one is still 20ms and another is 50ms),that means receive in a lower rate and store data in queue. I can see Elements in Queue
increase but the image data randomly lost, and the image synthesis speed is not reduced.
My question is why image data loss and I can't see the image synthesis speed reduced when change the delay value in consumer loop?
Do anyone know how to solve the problem? Are there any examples I can refer to? Any suggestions are greatly appreciated!
Attachments:
image1.JPG ‏56 KB

thisoldman,
I don't have '/usr/lib/modules/3.17.3-1-ARCH/build/Documentation/VGA-softcursor.txt' on my file system. Does it contain the info about changing the blinking speed?
P.S. The other two links I found yet before starting this thread. I only found in them the recommendations about changing "the color and shape of the cursor and turning blinking on/off" (as I mentioned in the original question). Did I miss the info about the blinking speed?
PPS: I found the vga-softcursor.txt here: https://www.kernel.org/doc/Documentatio … cursor.txt
But that file doesn't tell about changing the blink rate either.
Last edited by nbd (2014-11-23 20:55:41)

First attempt at Producer Consumer Architecture: continuous read and dynamically update parameters.

Hello,
I am currently working with two instruments; an Agilent E3646A and an NI 6212 BNC. My objective is to have the 6212 to be continuously taking measurements according to predefined parameters while the E3646A's parameters can be continuously updated. This simple instrument combination is intended to help me learn the necessarry achitecture; continuous measurement, dynamic output control, and more instruments will be added in the future.
I've previously posted on a similar, but more complicated, setup (http://forums.ni.com/t5/Instrument-Control-GPIB-Serial/Split-second-lag-when-controlling-two-instrum... and was advised to try the Producer Consumer Architecture. I've found relevant literature on the site (http://www.ni.com/white-paper/3023/en/, https://decibel.ni.com/content/docs/DOC-2431), searched the forums and constructed my own VI. While my first attempt at a Producer Consumer Architecture has resolved some of the issues I was having when I first posted on the subject, however, new issues have arisen with regard to reading and stopping the VI.
I am currently able to run the VI and update the device parameters. Previously, I would get a freeze while the instrument was being updated and could not toggle parameters until it was done. This has been resolved although the read only updates when a parameter has been updated although it is outside of the event structure. Furthermore the Stop button does not work in any context. I've also gotten occasional errors regarding the Deqeue Element but the bulk of the trouble is Error -200279 "Attempted to read samples that are no longer available" at DAQmx Read. I realize that there is a problem in my Producer Loop but haven't been able to figure out how to resolve it.
This is my first attempt at a Producer Consumer Architecture and already I can see that it is a powerful tool. I read as much as I could and looked at the relevant examples but expected to have some issues in the beginning. Would really appreciate any advice so I can take full advantage of the architecture.
Hope to hear from you,
Yusif Nurizade
Solved!
Go to Solution.
Attachments:
DCe3646A_DAQ6212_Prod_Con_4_13a_2014.vi ‏89 KB

Jon,
Thank you for the response and the suggestions.
I created the Local Variable for the Stop Button and moved the original into its own Event Case. It is now able to stop VI execution although I get Warning -1073676294 which I understand to be the buffer issue. The warning says that this was incurred on VISA Open for the E3646A's Initialize VI which is outside both loops, however, which I don't understand.
I tried increasing buffer size by decreasing the Number of Samples as per suggestions I found on NI forum threads. I've brought it down as low as 1 but the graph still only updates when an Event occurs and I keep getting the same buffer error. You suggested that the problem could be that they are in the same loop; does this mean that the DAQmx read should be outside both Producer and Consumer Loops or moved into the Consumer Loop? I found a couple of links ( http://forums.ni.com/t5/LabVIEW/Producer-Consumer-Design-Pattern-DAQmx-Event-Structure/td-p/2744450 , http://forums.ni.com/t5/LabVIEW/Producer-Consumer-Architecture/td-p/494883 -first response) on dealing with an Event Structure that my own VI is based. Alternatively, I found another link ( http://forums.ni.com/t5/LabVIEW/Producer-Consumer-Design-Pattern-DAQmx-Event-Structure/td-p/2744450 - first response) on a DAQmx Read with an Event Structure that places the graph in the Consumer Loop.
The core of my purpose in setting up this Producer Consumer Architecture is so that I could read continuously while the instrument parameters are updated dynamically so it's very important that I understand how this works. I am particularly struggling with how the Event Structure is controlling the While Loop's Execution.
Hope to hear form you,
Yusif Nurizade
Attachments:
DCe3646A_DAQ6212_Prod_Con_4_14a_2014_Edit_I.vi ‏90 KB

Can anyone tell me what's wrong with my queue or producer consumer loop?

A Labview engineer helped me with the overall structure of my program, necessitated by the fast data sample rate and post processing requirements. He recommended the producer/consumer loop and using one of the example files (Cont Acq graph voltage - int clk) to do the actual data acquistion. So I put together the loop and go my two channels of data acq going in the producer loop. However, nothing's getting picked up in the consumer loop and none of my data gets displayed over there.
Anyone care to take a look at it and let me know what I'm doing wrong?
Solved!
Go to Solution.
Attachments:
P-C Yanmar Program.vi ‏296 KB

Your Enque Element should be inside the while loop where you aquire the data. As it is now, the data has to stop being aquired before you send the last set of aquired data.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Time Stamps in Producer/Consumer Setup

I am trying to acquire signal from a Gas Analyzer, Flow Meter, and 3 RTDs. My hardware is a NI 9215 and NI 9217. I need to write the data to a file with a time stamp at which the sample was read. The program is written in a producer/consumer setup in which the data is being acquired in the prodcuer loop and sent to the consumer loop to be written. I can get the samples written to the file okay. However, I have not figured out how to put the time stamp in the data file correctly. I thought the time stamp was created with the corressponding measurement at the Data Acquisition VI. However, whenever I open the data file, there are only 0s in the time column. So, I've tried to use Format/Date String to add the time stamp. I can get it to work if I place it in the consumer loop. However, the time stamp is not accurate. It puts the same time stamp up to six digits of precision for two consecutive samples. I've tried to figure out how to add it to the producer loop, but I don't know how to add it and the measurements to the queue at the same time. Please tell me the best way to acquire signals with the exact time stamp and write them to a file using a producer/consumer design.
Example:
Date             Time       RTD1 RTD2      RTD3   CO2    Flow
5/26/07      5:20:01.25       57         56         56.5      100       0.5
5/26/07      5:20:01.30       57         56         56.5      100       0.5
5/26/07      5:20:01.35       57         56         56.5      100       0.5
Attachments:
Producer-Consumer From Scratch2.vi ‏75 KB

Okay, I've put it in a For Loop and it will connect now. However, whenever it runs the time stamp increments for a couple seconds and then it just repeats. How do I correct this?
Attachments:
Producer-Consumer From Scratch2.vi ‏88 KB
pleasework.txt ‏20 KB

Input and output on same device, producer/consumer structure

Hello interested people,
I have a question about using the same device for both digital inputs
and outputs. I have written a simple program of one while loop
that continuously polls the device, processes, and requests. I
have addressed the device using two DAQmx Asst. and I have attached
them with their error in/out cluster terminals to provide data flow and
eliminate the chance of addressing the devices at the same time (which
produces an error). Now I want to change this program structure
to a producer/consumer loop foundation with state machine.
In this design, I will have the DI in the producer loop and the DO in
the consumer loop, under one of the states. I can't simply
connect the error in/out ports in this configuration, so my question is
how to avoid the error caused by addressing the same device
simultaneously with two different tasks (input and output)? I
have attached two VI's, the "One Loop" vi is the original configuration
(simplified), and the Producer-Consumer vi is a NONSENSICAL program
that simply represents the desired configuration. (I don't need
any comments on the programming of this vi, it is only an example for
illustration of the problem).
I am thinking about bundling the input data and the error cluster, both
from the PXI 6528 DI, into one cluster, queueing that up, and
unbundling the de-queued elements for some kind of data flow between
the producer loop and the "Request" state of the consumer loop.
Is this the right approach, or am I barking up the wrong tree?
Thanks
Attachments:
One Loop DO DI.vi ‏102 KB
Producer-Consumer DI-DO.vi ‏106 KB

Hello,
It sounds to me like you really have two modes:
1. user interface actions determine execution
2. user interface is locked, and execution is automated.
I think it would make sense to use the producer consumer for an architecture. Basically you would do the following:
1. program the producer to handle the user interface as you normally would.
2. provide one additional event case in the producer which would be your "automated handling" case. In that case, you could put a state machine which could run until whatever conditions were met to put your program back in "user interface mode".
Keep in mind that you can use custom USER EVENTS to programmatically generate events ie. you can trigger the start of your "automated handling" form anywhere in your code at virtually any time.
I think this would allow you to take advantage of the producer consumer architecture in its intended spirit, while integrating an automated routine.
I hope this helps!
Best Regards,
JLS
Best,
JLS
Sixclear

Running subVI in parallel with itself using producer-consumer pattern

I'm using the procuder-consumer pattern to create what I call threads in response to various events much like in Producer Consumer with Event Structure and Queues
I have several physical instruments, and would like to run the exact
same test in parallel on each of the instruments. I have a subVI
that takes as inputs a VISA resource and a few control references among
other things and then performs the desired experiment. I have a
separate consumer loop for each physical instrument, with this subVI
inside each consumer loop.
My test VI worked great; each consumer loop was a simple while loop
incrementing a numeric indicator (not using my real subVI above).
However, my real program can only run one consumer loop at a time much
to my dismay. Reworking my simple test VI to use a subVI to
increment the indicator rather than just explicitly coding everything
resulted in the same problem: only a single consumer loop ran at a time
(and as I stopped the running loop, another would get a chance to
begin). The subVI in this case was extremely
simple taking only a ref to the indicator and a ref to a boolean to
stop, and incrementing the indicator in a while-loop.
Is there a way around this? Now that I've spent the time making a
nice subVI to do the entire experiment on on the physical instrument, I
thought it would be fairly trivial to extend this to control multiple
instruments performing the same experiment in parallel. It seems
only one instance of a given subVI may run at one time. Is this
true? If it is indeed true, what other options do I have? I
have little desire to recode my subVI to manually handle multiple
physical instruments; this would also result in a loss of functionality
as all parallel experiments would run more or less in lock step without
much more complexity.
Thank you.

You need to make your subvi reentrant. Then it can run several instances at any time with each instance occupying its own unique memory space. Click on File - VI Properties - Execution, and check the reentry execution checkbox. Then save the vi.
- tbob
Inventor of the WORM Global

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