Producer consumer troubles

I am in need of some serious help with my application of this VI template. Specifically I am looking for pointers on how to achieve the procedures described below. I am relatively still a beginner but I have simulated my set-up in the VI attached. My goal is to do the following
Move cars from any one lot to another following the gated channels by either
       opening the gates for a particular pathway based on the users selection of origin and final destination
       selecting individual gates to form a path
       generate error message when user selects the same location for starting point and destination
thanks
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Attachments:
Control 2.ctl ‏76 KB
Parking 2013.vi ‏109 KB

ok so I finally decided to use a template to implement the solution. Unfortunately certain sections of this template ( a good learning method I thought) are over my head but I have attached what I have done. My main concern though is to be able to send a sequence of digital outs by selecting various options (manual) on the front panel or using using the drop down menu to select current location and final destination plan to use the acquisition loop to determine and record which gates are open (digital in) from limit switches . I would like to use the recorded sequence to determine which gates are open and then reset them. My code is a work in progress and any informative pointers would be much appreciated.
Attachments:
Gates.zip ‏1742 KB
Sets.ctl ‏10 KB

Similar Messages

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
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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

Producer consumer loop array building

Hello,
I am trying to build an array in the consumer loop of a queued vi. This is the first time I have tried to use a producer-consumer structure since class many months ago. Each element is queued and sent to the consumer loop, and in that loop I want to build an array of the elements before I save it to disk. For some unknown reason I am having trouble accomplishing this. Usually I throw this stuff into a for loop, but here it isn't working.
I am converting the random number to a string in the producer loop because when I build the real program I will be using strings.
What am I missing?
Tay
Attachments:
Loop test.vi ‏35 KB

Just built your array in a shift register.
(The error case is simply wired across.)
Message Edited by altenbach on 05-16-2008 08:03 PM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
looptest.png ‏8 KB

Producer/consumer architecture over network variables with Real-Time target.

Hi all,
I am maintaining a producer/consumer data acquisition program to be deployed on a real-time target. The main code is deployed to and run on the real-time target during experiments, but was having trouble because the program was originally designed to write all experimental data to disk on the real time during acquisition, which puts the whole experiment at the mercy of the hard drive. I am now trying to rework the code so that the host takes care of logging, so that my time-critical loops don't have to wait.
I am currently using LabVIEW 8.5
I have two questions:
First, how can I programmatically call the data-logging subvi on the host so that it runs in parallel with the main vi which runs the experiment and collects data on the real-time? I have attached the test code that I have been working with to figure this out, but it does not run the logging vi continuously in the background. I am aware that there is better functionality for this in newer versions of LabVIEW, but I would prefer not to upgrade unless there is no other option. I would like to be able to run my data-generating vi and have it start the data logging remotely.
Second, is there a way in the host VI to read values off the network variable using an event structure rather than polling it for updates?
Any help would be sincerely appreciated!
Attachments:
testRemoteLogging.zip ‏124 KB

VI server
Mark the target VI as served on the machine on which it will execute and use VI server Call by reference to invoke the served VI.
This used to be taught as THE way to communicate syncronously with an RT app.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

AJAX producer/consumer and JAVA producer/consumer in same project

I've already successfully integrated and customized the code for both an AJAX and JAVA producer/consumer client in JMS (using ActiveMQ as the JMS broker and Tomcat as the webapp container). While both have been working well in separate projects, unfortunately, I'm having a bit of trouble trying to integrate them for the purpose of running an AJAX message listener and JAVA message listener in the same project.
What I'm trying to do is have JAVA act as the failover for when the AJAX JMS consumer is not listening (i.e. when the browser is closed). When a browser client opens, the (constantly running) JAVA client can ignore the messages... but... when no browser client is initialized, the JAVA client should respond to the messages on behalf of the AJAX client.
I've tried using a ServletContextListener pattern, which I was hoping would "automagically" launch the JAVA listener via its main method, whenever the Servlet gets initialized (i.e. it would auto-start when Tomcat gets restarted, or, anytime the Servlet gets redeployed) but it seems Tomcat is not thread-safe and this might be causing some problems.
In any case, I can't seem to get the JAVA client to reliably start running and stay running for the lifetime of my AJAX client (webapp .war), and without including them in the same project and same J2EE container sharing the same ServletContext, I don't know how its possible to ensure they are running and starting and stopping at the same time.
Is there perhaps a better way to accomplish this?
Edited by: bcmoney on May 17, 2010 1:25 PM

I've already successfully integrated and customized the code for both an AJAX and JAVA producer/consumer client in JMS (using ActiveMQ as the JMS broker and Tomcat as the webapp container). While both have been working well in separate projects, unfortunately, I'm having a bit of trouble trying to integrate them for the purpose of running an AJAX message listener and JAVA message listener in the same project.
What I'm trying to do is have JAVA act as the failover for when the AJAX JMS consumer is not listening (i.e. when the browser is closed). When a browser client opens, the (constantly running) JAVA client can ignore the messages... but... when no browser client is initialized, the JAVA client should respond to the messages on behalf of the AJAX client.
I've tried using a ServletContextListener pattern, which I was hoping would "automagically" launch the JAVA listener via its main method, whenever the Servlet gets initialized (i.e. it would auto-start when Tomcat gets restarted, or, anytime the Servlet gets redeployed) but it seems Tomcat is not thread-safe and this might be causing some problems.
In any case, I can't seem to get the JAVA client to reliably start running and stay running for the lifetime of my AJAX client (webapp .war), and without including them in the same project and same J2EE container sharing the same ServletContext, I don't know how its possible to ensure they are running and starting and stopping at the same time.
Is there perhaps a better way to accomplish this?
Edited by: bcmoney on May 17, 2010 1:25 PM

Producer consumer with analog and digital inputs and outputs

Hi everyone,
I am working on a control system program for some practical test work. Currently I am working on the data acuisition component of the Labview program. My architecture is produced-consumer loops with a que. My system will have analog inputs, analog outputs, digital inputs and digital outputs. It's not a time critical sytem, but I would like all of the data acquisition to be synchronised. I have attached my program as it is at the moment. I am having trouble getting all of the data into the que since I have two data types. Also, I'm not sure if i've synchronised the four read/write sequences correctly. I would greatly appreciate if somebody could take a look at my program and give me some advice. Thanks in advance.
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Attachments:
control_v2_DAQ loop.vi ‏46 KB

Robert, the specific error that I get is:
Error -200462 occurred at DAQmx Start Task.vi:6
Possible reason(s):
Generation cannot be started because the output buffer is empty.
Write data before starting a buffered generation. The following actions can empty the buffer: changing the size of the buffer, unreserving a task, setting the Regeneration Mode property, changing the Sample Mode, or configuring retriggering.
Task Name: Heater testing lab digital outputs
This error occurs at the 'DAQmx write.vi' function. I just want to sent one sample per second, for each channel. I would like the producer and consumer loops to each run once every second.
I have attached part of my code with just the data acquisition and writing. Any help would be greatly appreciated.
Attachments:
control_v2_ML_simple.vi ‏83 KB

Producer/Consumer Multi-Microphone Capturing

I was getting buffer overflow problems when I foolishly used multiple "Capture Sound" Express VIs to listen to several mics and process them.
I then created a producer/consumer structure where I produced 2 signals (2 producer loops) and processed them in 1 loop. It worked great!
I expanded this idea today to 3 microphones (and hoped for more later). Trouble is I'm getting errors again. I can't quite explain the errors, so I've attached images (in sequence). By highlighting execution, it seemed the error happens on the SECOND iteration of the "Sound Input Read" in each of the 3 "Producer" loops.
I hope someone can shed light on this issue. Seems strange that it would work for 2 mics but not for 3.
I briefly tried playing with the sampling rates with no apparent results.
Message Edited by ap8888 on 03-17-2010 07:43 PM
Solved!
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Attachments:
New2.vi ‏1074 KB

Here are the errors:
Attachments:
greenshot_2010-03-17_20-27-23.jpg ‏291 KB
greenshot_2010-03-17_20-27-34.jpg ‏503 KB
greenshot_2010-03-17_20-29-01.jpg ‏253 KB

Measurement and control via Producer/Consumer

Hello folks,
Iam trying to realise an automated projekt, for testing an actuator.
It has to Measure the Signals, process them and also has to create signals controling the actuator.
So far no Problem....But,it also has to run trough 3 or more Test-cycles of wich each has different ControlSignals.
(example: Test1 - input: 40VSin(40Hz), Test2 - input:Triangle, Test 3 - input: 100Vsin(100Hz)
It still doesnt sound quite difficult, but as an LabView beginner, i´m having a lot of trouble finding the Right Structure to realise all This. normally i use SPS systems, but this time it has to be Labview
Had some trys an hav uploaded them.
But The Producer/Consumer Structure makes some Problems. It doesnt give out any Signals from the ProducerLoop. :/
Is there any outher way programing Labview more efficient for that Problem ?
Sorry 4 the bad English
Greetings
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Attachments:
ProcessTest2.vi ‏129 KB

MarioMueller wrote:
Hello folks,
Iam trying to realise an automated projekt, for testing an actuator.
It has to Measure the Signals, process them and also has to create signals controling the actuator.
So far no Problem....But,it also has to run trough 3 or more Test-cycles of wich each has different ControlSignals.
(example: Test1 - input: 40VSin(40Hz), Test2 - input:Triangle, Test 3 - input: 100Vsin(100Hz)
It still doesnt sound quite difficult, but as an LabView beginner, i´m having a lot of trouble finding the Right Structure to realise all This. normally i use SPS systems, but this time it has to be Labview
Had some trys an hav uploaded them.
But The Producer/Consumer Structure makes some Problems. It doesnt give out any Signals from the ProducerLoop. :/
Is there any outher way programing Labview more efficient for that Problem ?
Sorry 4 the bad English
Greetings
your architecture is hard to follow. i think you can do this with a state machine..write out your test requirements in steps and what requirement you need to transition. be more specific in describing your problems (error messeges?)..

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)

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

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!
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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

Producer consumer troubles

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