Using Warmup Samples to Initialize.

[MSATLAB]

Hello,

     I am currently integrating another communication program with National Instruments RTOS and we are running into a few problems regarding the first time step.  The communication program initializes during the first couple time steps and is obviously making the RTOS not match real-time time steps.  We can do a soft real-time operation by not tieing hardware to the simulation.  In that case the first couple time-steps are not real-time and the NI RTOS doesn't really have a problem with it because the rest of the model can meet the time step requirement.  The model is just a simple Simulink model, that is pretty much a dummy model for testing purposes.  I believe that if we were able to ignore, or use the 'warmup samples' we would be able to over come this initial problem and everything would be able to run smoothly.  I know there is a Property Node property for the 'DAQmx Real-Time' that is the 'Warmup Samples'  but I have been unable to select the property, for reasons unknown to me. (I found this option in the help.)  None of the possible properties for the 'DAQmx Real-Time' Property are selectable.  I am not sure if I am putting the property node in the wrong section of the driver VI or if I am just not going about this the right way.  Just for further clarification, I am using a Simulink Model in LabVIEW SIT and am modifying the driver vi for the model.  Any help would be greatly appreciated.

Michael

LabVIEW 8.5

SIT 4.0

[Karunya_R]

Hi Michael,

I am guessing you are referring to 'Warm up iterations' when you say 'warm up samples'. The are two way to access the DAQmx RT Property node for Warm up iterations. One way is to drop the DAQmx RT property node on the block diagram, single click on the white portion of the property node, five options should pull up. And one of them should be Warm up iterations. The other way to access is to pull down the white part. Then should be able to see all the five options.

I also wanted to mention that if you do use warm up iterations, it can change your loop iterations resulting in some of them running late due to jitter. One outcome of this is that it can halt your simulation itself (this is when you are not in RT). This happens because there is nothing in the buffer to use for the simulation and it waits until you get new data to write to the simulation. If you are in RT, SIT overwrites the buffer resulting in gaps in the data. Please check this help file.

What RT hardware are you using with this? Are you still using SIT when you are not in RT portion of your program?

[MSATLAB]

Hello,
     First off thank you for the response.  I do mean 'warm up iterations.'  I have actually figured out what was the main problem.  As we all know, or at least are finding out reading this, is that DAQmx contains an error in version 8.6.0f12.  This was creating the problem of not allowing us to select the 'warm up iterations' as a choice when we dropped a property node for the RT task.  So once we downloaded and upgraded the DAQmx version, everything worked fine.  Thank you again for the help.

Michael

[MSATLAB]

I guess I have another update after a few days of using the new DAQmx and the "warmup iterations."  The problem seems to still come around and we called the NI support team and they have yet to come up with an explanation.  We currently have to restart our machine and hope that the option becomes available when we load LabVIEW up again.

Michael Boyd

[Karunya_R]

Hi Michael,

I am guessing the problem you are referring to is the one about 'number of warmup iterations' property node being missing. I have tried this multiple times on my computers and other computers here and have not able to replicate your issue. Please let me know if I have misunderstood your problem. If that the case, is there a pattern to when this happpens?

[MSATLAB]

I can lay down a property node and select the RT section of the property node, but as soon as I try to select what property I want this node to control no options come up.  It is just blank where 'warmup iterations' would be.  Thank you.

Michael

[Karunya_R]

I think it might just be due a bad install of RT. Have you tried reinstalling RT?

[MSATLAB]

Yes, we reinstalled the RTOS on the machine and to no avail the problem was not fixed.  I guess it is more of an inconvenience, but quite a awkward one at that.

Michael

[Karunya_R]

Hi Michael,

It is possible that you might have run into a bug in LVRT 8.5 (or is it LVRT 8.5.1). Can you please post screen shots of your problem?

You did say that you get the problem intermittently.

Is there a pattern to this?

Do you get an error message/log/report when you shut down LabVIEW after this happens?

[MSATLAB]

Hello,

Thank you for responding. It seems that we figured out the problem. If we open the driver VI on the host machine, there are no available options for the Real-Time Property Node. However, if we open the driver project and then the VI from inside the project, the Property Node works as expected.

Thanks,
Michael