Producer consumer waveform x axis

I've run into a problem and I'm not sure of the source. I'm developing a program that reads, displays, and writes thermocouple readings at different rates. I'm using the producer-consumer architecture and while the sample rate will not be an option, the refresh rate of the chart that displays some of the temperatures will be controlled by the user. I've been working with the attached example trying to understand where the problem lies with no luck. The consumer loop is set to wait 2 seconds which I can tell it does but the x-axis still counts every second. How do I sample from the producer loop and have the correct time and temperature displayed by the chart in the consumer loop?
Thanks.
LabVIEW 2012 - Windows 7
CLAD
Attachments:
Plot Starting at Zero Seconds-2.vi ‏31 KB

Sorry I can't look at your code right now as I am still waiting for my beta copy of LV for Android to arrive -- but seriously the x axis of a graph increments by 1 unless you set the multiplier property to something else.
Mike...
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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

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.

Producer consumer loop only execute once?

Hello here,
In my VI, the producer loop seems working continuously, but the consumer loop only execute once.
I haven't used producer/consumer pattern before, could someone give me some ideas why this happens?
My code is in attachment.
Thank you in advance.
Yaqiong
Solved!
Go to Solution.
Attachments:
parallel - Copy.vi ‏72 KB

That would be the poor choice of using an event structure in the consumer loop. As set up you must generate a mouse Leave or mouse enter event on Waveform Graph for the consumer loop to finish its first iteration.
Delete the event structure. you don't need it to update a graph.
Jeff

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

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

Producer/Consumer Design Pattern with Classes

I'm starting a new project which involves acquiring data from various pieces of equipment using a GPIB port. I thought this would be a good time to start using Classes. I created a GPIB class which contains member data of: Address, Open State, Error; with member vis such as Set Address, Get Address, Open, Close...general actions that all GPIB devices need to do. I then created a child class for a specific instrument (Agilent N1912 Power Meter for this example) which inherits from the GPIB class but also adds member data such as Channel A power and Channel B power and the associated Member Functions to obtain the data from the hardware. This went fine and I created a Test vi for verfication utilizing a typical Event Structure architecture.
However, in other applications (without classes) I typically use the Producer/Consumer Design Pattern with Event Structure so that the main loop is not delayed by any hardware interaction. My queue data is a cluster of an "action" enum and a variant to pass data. Is it OK to use this pattern with classes? I created a vi and it works fine and attached is a png (of 1 case) of it.
Are there any problems doing it this way?
Jason

JTerosky wrote:
I'm starting a new project which involves acquiring data from various pieces of equipment using a GPIB port. I thought this would be a good time to start using Classes. I created a GPIB class which contains member data of: Address, Open State, Error; with member vis such as Set Address, Get Address, Open, Close...general actions that all GPIB devices need to do. I then created a child class for a specific instrument (Agilent N1912 Power Meter for this example) which inherits from the GPIB class but also adds member data such as Channel A power and Channel B power and the associated Member Functions to obtain the data from the hardware. This went fine and I created a Test vi for verfication utilizing a typical Event Structure architecture.
However, in other applications (without classes) I typically use the Producer/Consumer Design Pattern with Event Structure so that the main loop is not delayed by any hardware interaction. My queue data is a cluster of an "action" enum and a variant to pass data. Is it OK to use this pattern with classes? I created a vi and it works fine and attached is a png (of 1 case) of it.
Are there any problems doing it this way?
Including the error cluster as part of the private data is something I have never seen done and ... well I'll have to think about that one.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Producer/Consumer Architecture

Hello All,
I am currently working on an application using State Machine Architecture where I have to monitor various parameters (7 temperature values & 3 pressure values), along with this I have to On/Off a Clutch using a digital Output for set time (e.g. On for "X" seconds OFF for "Y" seconds), but as soon as the pressure and temperature values go beyond upper or lower limits or whenever the user presses the Emergency Stop (that means I have to monitor Digital Input as well) so I am moving to different error cases depending on which values go beyond limits or emregency pressed etc..
But this realisation is not working fine as I have to monitor and control several other things in addition to acquiring data....till now I just have used State Machine Architecture, I have seen Producer/Consumer Template but not quite sure how to realise such kind of application which involves data acquisition along with user interaction and monitoring.
Could someone please put some light on giving similar kind of example or what else I can try with this problem.
Regards
James

Hello James,
A Producer/Consumer architecture will certainly do the trick for you. I am sending you an example that has the Data Acquisition section in the producer loop. However, you can also put your User Interface in the Producer loop and have the Data Acquisition in the Consumer loop. The Queues are used for sending data from the Producer to the Consumer(s) loop(s) (you can have multiple comsumer loops).
You will just have to design specific cases to react to different user inputs.
By the way, this example is from LabVIEW Basics II training course. If you have never taken LabVIEW Basics I and II, I highly recommend them. You can self-pace the class or take it with an instructor.
LabVIEW Courses
Hope this helps!
Message Edited by Kalin T on 03-23-2007 09:57 AM
Kalin T.
National Instruments
Attachments:
ImplementedProducerConsumer.zip ‏250 KB

Producer Consumer Start Trigger

Short Explanation: I'm using a 3rd party device to send a TTL signal to use as my start trigger in my VI. My cDAQ and modules appear to have the ability to send a start trigger independantly but I have been unable to hunt down how to do this in a producer/consumer system. I do have an idea at the bottom of the long explanation.
Long Explanation:
I'm running a test system that monitors the pressure wave from a hydrogen/oxygen ignition. Components are a cDAQ-9188 with modules 9222 (x3 high speed AI), 9481 (x2 relay), 9402 (x1 I/O Module), 9221 ("Low" Speed AI).
Based upon recommendations in this forum I've placed my DAQ in a producer/consumer architecture.
At this point the system mostly works, I still have a few more things to add for all the information I want to collect. However, it records at high speed and the 9221 and the 9222 modules are synchronized. It has successfully collected good data as of this writing.
When the system starts it will monitor, but not record. I need to fill the test structure with gas to a specific concentration before I ignite/record. When I press the record button I send a TTL signal from the 9402 to my high speed camera and I close a relay on a 9481 which engages a spark system. The spark system takes a variable amount of time to charge and fire so I have a timer that leaves the TTL and the relay active for a half second.
My problem, and it's a small one, comes in with the monitoring system and the synchronization. In order to get the system to synchronize properly I had to generate an external pulse into PFI0 to use as a trigger. I attempted to assign the various clocks available as a start trigger but I ended up with unsynchronized data.
Is there a way to generate a pulse on my 9402 to use as a trigger? It feels silly to me to use an external device when I have something that can generate the signal I need.
In thinking about this post I might have solved my problem, at least in my head. I'm thinking I can move the TTL output VI (which I will eventually change to DAQmx) into the producer loop and move my true/false statements to the consumer loop as a 1D array within my queue to start the record. Probably more to it than that but I can only learn by experimentation right?
Thoughts? Recommendations?
VI attached.
Solved!
Go to Solution.
Attachments:
HUCTA Controls.vi ‏186 KB

You can't generate a pulse with the 9402 itself. The pulse would actually be generated by the 9188. You should create a Counter Output task to generate a pulse train. Try the attached example as a start point to experiment with the counter.
This Vi is for LabVIEW 2013, if you have an older version let me know and I will try to convert it.
Camilo V.
Applications Engineer
National Instruments
www.ni.com/support
Attachments:
Pulse Train Generator.vi ‏18 KB

Producer consumer waveform x axis

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