Ethernet/IP: LV Loop Priority

Have an application that has 3 VIs that deal with Ethernet/IP Industrial protocol.
I was looking into the determinism, and asking questions of NI's Ethernet/IP guru.
'Fast' Ethernet/IP data was in a timed loop with a priority of 3000 (highest). But in emails with NI is seems the Ethernet/IP stack operaties at a priority somwhere beneath timed loops - so the following suggestion was made....
My question is how to set conventional while loop 'LV high priority' as mentioned below....
LV Core 1 training stated not to use VI priorities when using timed loops - so I have not. But I am not sure that 'LV high priority' even refers to VI priorities. And connot see context sensitive setup for a conventional while loop that speaks to priority.
...may have been incorrect about the ability to change the network thread priority via an INI token. It seems that the default (which may be the only option) is that it runs below Timed Loops but higher than LV's "high" priority and higher than the thread used by the EtherNet/IP thread. I would therefore suggest if you have loops that purely interact with the EIP stack to set them to LV high priority rather than in timed loops because it really never makes sense for that loop to preempt the network stack or the background EIP thread. This would remove one more source of jitter.

Hi S1ack,
I believe the bolded sentence was referring to one of two things.
1: Use wait functions in the lower priority loops as described in the section "Parallel Block Diagrams" Here:
http://zone.ni.com/reference/en-XX/help/371361H-01/lvconcepts/vi_execution_speed/
2. Setting the SubVI's Priority by opening the VI, File>>VI Properties>>Execution as explained this link:
http://digital.ni.com/public.nsf/allkb/44AB5BEDC20CB43C862565D4000D9885?OpenDocument
DylanC

Similar Messages

How do I set while loop priority in an RT Field Point application?

I have a vi that I want to run in an FP2010 that contains 2 while loops, one must be Time Critical priority and the other Normal or lower priority. I will be using RT FIFO to transfer data between the two loops. The Normal loop will be used for communication with a Host PC.
How can I set the priorities of these 2 loops?
Can I run 2 separate vi's in the FP with each set to a different priority And transfer data between the two with RT FIFO? How?
I am using V6.1 and the customer does not want to spend on upgrading.
Thanks,
Chris

Chris,
You are on the right track using two separate VIs with different priorities and using RT FIFOs to communicate between the two. Please see the following tutorial and the related links, one link of which is an example with a zip file containing the RT FIFO VIs for LabVIEW 6.1.
Doug M
Applications Engineer
National Instruments
For those unfamiliar with NBC's The Office, my icon is NOT a picture of me

Priority limits on a timed loop

Hi,
With reference to the value of priority in a timed loop, the help says that this value must be between 1 and 65,535.
Anyone know what these limits are referred?
Thanks for your time...
Solved!
Go to Solution.

amflores wrote:
Hi,
With reference to the value of priority in a timed loop, the help says that this value must be between 1 and 65,535.
Anyone know what these limits are referred?
Thanks for your time...
Timed loops run in a dedicated execution system at a priority above high priority but below "Time Critical" if there is more than one timed loop running the timed loops priority value is used to signal the OS which loop should get the larger amount of processor time. The lower the number the higher the priority requested. Some OS's even respect that number. Some do their own scheduling anyway.
Jeff

Ethernet and WIFI Question

This maybe a redundant question, I want to back up the stuff in my Imac using TC. I do not want to use this Imac wireless nor do I want my backups done wireless but can I still use the wifi system on TC for Ipad ,Nook, etc. without having to configure my Imac everytime to use a wifi devise?

Yes. Just connect the iMac to your Time Capsule with an Ethernet cable, then go into System Preferences->Network and either set Ethernet to a higher priority than AirPort, or turn off AirPort completely.
Your wireless devices will continue to connect to the internet, and even to your iMac, through the Time Capsule wirelessly, while your iMac will enjoy the faster speeds and improved reliability of the wired ethernet connection. Your devices which connect to your iMac "wirelessly" will continue to do so; they will not know the difference between your iMac on the Time Capsule's wireless network and your iMac on the Time Capsule's wired network – it's all the same as far as connectivity is concerned.

Time Capsule Via Ethernet (PC)

Hey guys,
I've my TC working nicely over the wireless network (Vista), but I can't for the love of me connect to it via a ethernet cable... Backuping is really slow through wireless so I really need to get it working plugged in!
I've tried plugging the ethernet cable into both different ports on the TC, can someone confirm which port I need to plug it into? I'm guessing it's any of the device ports, as the first ethernet one, is for connecting the TC to a modem, right?
After I've done that, what else do I have to do?? I'm going out of my mind trying different things but nothing seems to be working..
Please can someone help!
Thanks

Don't know Windows but yes connect to the lan port. If Windows is similar to Mac about networking then on a Mac if under the Network pane, if Airport (wireless) is et for priority then ethernet takes second place. I move ethernet up on the priority list or just turn Airport off. Check for that under Vista.

(Trouble printing) Trouble with connection between Macbook Pro and Hp Deskjet 1510.

Trouble with connection between Macbook Pro and Hp Deskjet 1510. (Nothing Prints).
I have a Macbook Pro and am having difficulty printing documents from ‘Pages' from my Hp Deskjet 1510. I have installed the necessary software for the printer and it is connected via USB. Every time I try to print the printer icon comes up as it should, 'printing' and then 'job completed' and then the icon disappears. (Nothing is printed.) I thought it might be something to do with Pages compatibility with the printer but exporting the document to Word or making it a PDF doesn’t change anything. I don’t have Microsoft Word on my computer. The scanner does work and when I printed a ‘Test Page’ that worked too.
Let me know if you know why this is happening.

With these settings the network now works flawlessly, however, when i have my ethernet cable plugged in, my internet access via my airport card(on the macbook pro) is no longer available. Hoping you can tell me why this would be with this info i've provided.
Educated guess. The networking devices have priorities as to which are used. The standard order is that Ethernet has a higher priority than Airport.
While your Ethernet is unplugged it is inactive and the Mac ignores it. Once you plug it in, the Mac sees that it is active and switches traffic to that interface.
I actually take advantage of this feature at home, but configuring my Airport and Ethernet with identical fixed IP addresses. Normally I'll use Airport, but if I'm copying a huge file and I want faster performance, I'll just walk my MacBook (previously iBook, previously Powerbook) over to my Ethernet switch and plug in my MacBook. Magically, the Mac detects that the Ethernet is active and continues the file transfer uninterrupted over the faster 100baseT Ethernet connection. When the transfer is finished, or if I really need to move back to the Comfy Chair, I unplug the Ethernet cable, and all activity reverts back to the Airport, all without disrupting any existing networking connections.
You on the other hand have totally different settings for your Ethernet and your Airport, so when you switch to Ethernet, you basically loose your Airport connections.
Something you can try:
System Preferences -> Network
Gear icon on the bottom left, next to the [+] [-] icons.
Select *Set Service Order...*
Now Drag the network interfaces into the perfer priority order you want. In this case put Airport above Ethernet.
NOTE: You may want to create a new Network Location for this, instead of messing with your normal home Location (which is most likely the default Automatic. That way you have your original you can always fall back to.

Binary write to file slowing down my program

I have noticed this more on some types of computers, but I have two threads going. One that captures 10MB images and queues them, and another thread that dequeues them and appends to a binary file.
If I disable the write to file, program chugs along well. Once enabled, I noticed that the image capturing begins to act sluggishly, almost in sync with the writing to hard drive. I have tried changing the write loop priority to the lowest as well.
It isn't holding up at the queue/dequeue step either. Any pointers on what to try? I'm almost certain that there is a memory sharing issue where one process is writing to 10MB image to memory, while the other is reading a 10MB image from memory, and this is tying things up.

dre99gsx wrote:
The main VI which hosts both of these loops is setup as User Interface
There's the problem, I think. The user interface subsystem is special - it's a single thread. This is required for certain things (interactions with the operating system and user interface, some external DLLs and ActiveX components) that require a single thread. In general, don't run your code in the user interface system unless you have a specific reason to run it there. As an example, property nodes that refer to front-panel items cause a switch to the user interface thread, so if you have VI that uses a lot of references to update the front panel, that VI should run in the UI system. In your case, if you switch your main VI to Standard and leave the subVIs set as Same as Caller, I think you'll see a similar speed improvement. There's more information about LabVIEW threading here, although that information is slightly out of date; if I remember correctly (couldn't find the reference in a quick search) LabVIEW now allocates as many threads per system as there are processor cores in your CPU, but not less than 4 per execution system with the exception of the user interface.

CRIO9074 RT jitter every 10 sec. when writing data to SD card through 9802 module

Hi,
I am trying to use cRIO 9074 to collect data from different sensors at 50Hz and log the data to SD card plugged in 9802 module. I use FPGA- scan interface hybrid mode because some sensors are just based on analog signals and others(i.e.. IMUs) are based on RS232. This structure worked well. I used to transfer all the data to host VI in my desktop and log them there.
Recently, since I have more and more sensors, I decide to log all the data locally to SD card on cRIO 9074. However, I have a trouble.
I found my data are not continuous and always miss one second after ever other 10 seconds. So I tried to insert a FIFO to buffer the data between two timed loops. The high priority loop is in charge of collecting data and the low one is in charge of writing. But the problem still exists. Actually, the problem has nothing to do with FIFO because 50Hz is slow and I have validated that 9074 can collect and write all data within 10ms(100Hz). Even with out FIFO, the program should work.
Finally, I find out an phenomenon that both the two interaction variables "i" in the two timed loops will periodically stop for one second after every 10 second( I check them through front panel and probe). At the same time, the CPU usage increase dramatically and after one second, it will go back to normal level. That means the RT jitter every other 10 seconds and cannot work at this instant. If I fully delete the SD writing blocks, the problem is gone and the system works very smoothly. So most likely, the problem is due to SD card module.
I tried different ways, i,e, changing the loop priority, clock resources, the size of fifos. Nothing works. I even reduce the system frequency by two to 25 HZ, and even by 5 to 10 Hz. The problem still exists.
Attachments are two CPU usage check at 50HZ and 25HZ. Usually it is below 80% at 50HZ so that the capability of CRIO9074 is not a problem at all.
And I also attach my RT VI which is messy, because I almost go crazy thess days due to the problem . Does anybody have chance to check is there anything wrong in my VI? Or do I need to change the configuration of CRIO 9074 or update the RT engine? It seems like a hardware problem.
Does anybody face the same problem before?
Yizhai
Rugers Univesity

Hi,Zach-H,
     Thanks. Actually, my problem is already solved after I contacted one NI engineer online.
     I shouldn't use timed loop to write SD card.   Because SD card batch writing is time consuming and its priority can't be high. "while loop" is good for SD card writing.
   Yizhai

Pause frames on blade interfaces, what is expected?

I am putting together a UCS runbook for an operational team to use to help with troubleshooting Cisco UCS. I was leveraging some Cisco Live presentations including 'BRKCOM-3002 - UCS Performance Troubleshooting'. In this presentation, when looking at congestion inside UCS the presenter makes a reference to check for pause frames...in this customer's environment I ran the same command for documenting the procedure and noticed many Tx pause frames. Is this normal? Unfortunately I have never checked these counters in other environments so I have nothing to base it off. There are 0 pause frames on LAN uplink interfaces and only a few 100 pause frames on the server downlink interfaces to the FEX. This environment is running VMware ESXi 5.5 U1.
ucs-A(nxos)# show interface ethernet 1/1/1 priority-flow-control
============================================================
Port Mode Oper(VL bmap) RxPPP TxPPP
============================================================
Ethernet1/1/1 Auto On (18) 0 607998
As you can see there are many pause frames being sent from the blades...
Ethernet1/1/1 Auto On (18) 0 607998
Ethernet1/1/2 Auto Off 0 0
Ethernet1/1/3 Auto On (18) 0 647302
Ethernet1/1/4 Auto Off 0 0
Ethernet1/1/5 Auto On (18) 0 686730
Ethernet1/1/6 Auto Off 0 0
Ethernet1/1/7 Auto On (18) 0 613622
Ethernet1/1/8 Auto Off 0 0
Ethernet1/1/9 Auto On (18) 0 447698
Ethernet1/1/10 Auto Off 0 0
Ethernet1/1/11 Auto On (18) 0 479446
Ethernet1/1/12 Auto Off 0 0
Ethernet1/1/13 Auto On (18) 0 429074
Ethernet1/1/14 Auto Off 0 0
Ethernet1/1/15 Auto On (18) 0 406480
And 0 pause frames on LAN uplinks Eth1/1-4 and not many on the server downlinks Eth1/9-16.
Ethernet1/1 Auto Off 0 0
Ethernet1/2 Auto Off 0 0
Ethernet1/3 Auto Off 0 0
Ethernet1/4 Auto Off 0 0
Ethernet1/5 Auto Off 0 0
Ethernet1/6 Auto Off 0 0
Ethernet1/7 Auto Off 0 0
Ethernet1/8 Auto Off 0 0
Ethernet1/9 Auto Off 96 414
Ethernet1/10 Auto Off 16 362
Ethernet1/11 Auto Off 24 410
Ethernet1/12 Auto Off 18 452
Ethernet1/13 Auto Off 26 318
Ethernet1/14 Auto Off 402 354
Ethernet1/15 Auto Off 876 308
Ethernet1/16 Auto Off 114 310
If I am pointing operational administrators to go check counters then I want to be clear what are expected returns. Any insight is appreciated.
Cheers,
Matt

Have a look at
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/troubleshooting/guide/N5K_Troubleshooting_Guide/n5K_ts_fcoe.html
I have seen this in multihop FCoE installations, specially with problems of FCoE disk arrays.

Drawback of putting producer and consumer in one loop. [Ethernet IP]

The "Create Assembly Instance" exapmple vi have two separte loops. One for the input (producing data) and the other for the output (consuming data). Would it be possible to combine everything into one loop? Are there any drawbacks to using one loop for the input and the output?
and i know one drawbacks will be that both consumer and producer will have to have the same rate..

That's an interesting piece of code. It's not so much a producer/consumer as it is two separate loops handling input and output. Take a look at this link to see what producer/consumer is: http://www.ni.com/white-paper/3023/en/ You can also find the code by going to File->New and opening the "From Template" folder under VI.
What controls your state machine? With events not being possible on a RT system, I'd expect you'd have some form of polling. Polling would still use a time period between polls. Granted, the network requirement would definitely break determinism, as you've already noted. If you're doing this, why not put it into a timed loop? Timed loops aren't always determinstic. That's why there is a "Finished Late?" terminal. It's not the loop that makes the code deterministic, it's the way you put your program together. By moving it into a timed loop, you gain the ability to give it a priority. I'll explain why this is important in a minute.
You're welcome to combine the two into a single loop if you still meet your timing requirements. That's a design choice that is up to you. I don't know what your other Ethernet/IP "stuffs" is, but I'd likely combine this into my output loop if possible. I'm assuming it has something to do with the data you care to send.
The overhead from the loop isn't enough to worry about the worload on the CPU. Ultimately, the code within the loop determines how rough you're being on the CPU. That's true in one loop or in four loops. Splitting code into multiple loops just lets you prioritize code. If everything is in a single loop, it all must run before the next iteration. If your code is split into ten loops, as an example, only what is inside each loop must be run on that loop's iteration. Using priority, as you've mentioned, ensures you determine which loop runs first. Let's say that loop completes and gives the other loops time to run on the CPU. Before they complete, the loop wants to run again. The CPU will go back to that loop and run. By splitting the loops up, you've ensured this piece of your code will run even if the CPU can't handle processing all of the code within that period. Rather than hurting determinism, you've aided it. The parts of your code that you aren't worried about being deterministic happen when the CPU has time for them. The parts that you NEED to be deterministic happen deterministically and push those other parts of the code out of the way.
Looking at the example code you're showing, I'd really want to know what it is you plan to do with the code and what you need to be deterministic. I'd assume you plan to read the data, process it, and send a corresponding output. If you need ALL of this to be deterministic, I'd put it within a single loop or use queues to send data from the input loop (commented as consumer) to the output loop (commented as producer). This decision would really just depend on how fast you care to acquire data and how deterministic you desire the output to be. Without using the queues, you create something called "race conditions." When you send an output, is that related to the newest input or one before it? You simply cannot tell.
Jeff B.
Applications Engineer
National Instruments

How do I correctly time while loops using SCPI and VISA/Ethernet communication to send DC current Values to a Power supply?

I'm rather new to using labview and I having an
issue with a test Data Aquisition lab I'm trying to setup using a
Keithley 6221 AC/DC current source and a basic PCI M-series NI-DAQmx.
First of all, I'm looking to update the current value on a power
supply at a rate of atleast 10Hz and I'm using SCPI commands and VISA
communication through ethernet to do so. Attached below is the VI I
have written.
The issue I'm having is this:
My VI will
loop through the values fine in software, or so it seems. I am unable
to get the Power supply to update sequentially if I don't set my loop
delay to anything greater than 130ms. If I try to run the loop faster
it starts skipping values instead of counting 1,2,3,4,5,1,2,...etc. it
goes 1,2,4,5,2,4,1,2 on the display of the power supply and my DAQ unit
also skips these values so I know that the number just isn't getting
read to the Power supply in time. I was wondering if this was due to
my sloppy programming or if it is a hardware issue, my computer or the
method of communication to the power supply? Is this due to the fact
that I'm using ethernet and VISA communication? Is there a faster way
to communicate or is GPIB faster? Any input at all would be extremely
helpful.
On a side note: Right now I'm using an pre-determined
array of values that I can update on the fly but in the future this
with be put into a closed-loop control system. The value for the
power supply output will be determined by the loop and sent that way.
Attachments:
basic DC loop 6221 Keithley.vi ‏145 KB

Also, one of the string constants is NOT set to '\' Codes Display. Here is an alternative method of calculating the index. I removed the DAQ and VISA stuff since I could not run it.
Lynn
Attachments:
basic DC loop 6221 Keithley.2.vi ‏16 KB

How do I set priority of a While Loop in RT in a FP2010?

Sorry about a duplicate post. I could not find my post from last night.
I want to run a vi with 2 while loops in my FP-2010 with different priorities. One is time critical running a PID, the other is low priority for communications with a PC host.
How do I set the priorities?
Thanks,
Chris

Put the two loops in two different VIs. Go to the VI properties and set the priority there under Execution priorities.
In other words, you can set the priority at the VI level and not at the While-loop level. However, if you want this at the loop level, you may want to take a look at the new Timed Loops.
Hope this helps.
-Khalid
Message Edited by Khalid on 12-02-2005 06:31 PM

High priority settings cannot precisely time loops?

I have an loop that acquires data every n milliseconds and casually sets some digital output when a threshold has passed.
This digital-out is quite time-critical thus I don't like to do a on-board-acquisition but get each data just in time.
That's very fine with a 1ms loop-time as long as Windows NT has enough ressources. But if there's another time-consumptive process running, things get bad.
I started a "search for file" and parallel my application. Now Windows shared the timeslices and I have a lot of acquisition-dropouts for 10-20 ms.
So I set the VI-priority to "highest" and the WindowsNT-process priority for LabView to "realtime". At least the latter should get the VI all the time it needs.
But LabView se
ems to be fair enough to still share ressources and the dropouts continued.
Can I set my LabView-application so that it gets absolute priority in Windows NT to have a constant acquisition?
Thanks, Daniel

You can go to hardware timed acquisition or LabVIEW-RT. Windows, Linux, Mac, etc. are not deterministic operating systems. There is a lot of information on "real-time" acquisition at NI's site. Try doing a search and seeing what your options are. Good Luck.

Airport connection taking priority over Ethernet

There have been similar posts about this, one of which is marked as answered so I can't reply to that.
I am running within my company and may Macbook is connected via Ethernet to the network. I have a Time Capsule doing wireless backups. The Time Capsule is also connected to the network via Ethernet to provide me with a personal WiFi point (so I can use if with my iPad etc).
However I noticed that wireless connection is taking priority over the wired Ethernet, effectively making the Ethernet wired connection to my Mac redundant. Whilst this doesn't really result in a massive performance issue, it would be best to use Ethernet whenever connected.
I checked System > Network > Set Service Order and Ethernet is above AirPort.
Any ideas?

Hi,
Welcome to the  Discussions
I read this as no-one seemed to have made a reply.
I ma not sure I have the answer but I do have some questions.
Those answers may provide some insight to someone that can help.
Are you saying that effectively you have a Modem and possibly a router that serves the computers at your company ?
Separate from this a Time Capsule is also on this Network.
You say Wireless backups.
Does this mean the Setting in System Preferences > Network differ between the Airport Card settings and the Ethernet Card Settings ? (Different "router IP" Listed)
Could you explain how the Computer is therefore doing Wireless backups ?
If you are Ethernet to the regular router and then Ethernet from there the to the Time Capsule I don't see how it was set up for Wireless.
Was the Time Capsule set up to Extend the regular Network ? (Join an existing Network or if set up manually, the drop down in the Internet pane read "Bridge (Off) Mode")
The System Preferences > Network Settings would be the same except for the Airport Cards IP Address and the Ethernet card's IP address in this case.
From there where are you getting the info that the Wifi/Airport card is taking priority ?
Setting the Sort Order needs you to Drag things down the List or only up to second place (you cannot drag to the top directly).
You do seem to be saying that you have achieved this.
The Mac Help on this does not say that one will override the other - just that it will try the top one first.
10:01 PM Wednesday; March 23, 2011

Ethernet interface priority explanation

I'm looking for an explanation behind the solution to a problem I recently faced. My configuration (this is on the latest Xserve w/ 10.5.6):
Ethernet 1
- NAT'd, static IP
The Xserve was not providing NAT services to the local subnet. A linksys router with another static IP was acting as a gateway to the local subnet.
Ethernet 2
- public, static IP sitting behind a T1 router
The problem I had was that initially I had configured Ethernet 1 as the "primary interface" so that the server "looked in" rather than out by default. Consequently, I was unable to ping the external IP on Ethernet 2 from my home server (via and SSH connection). (At one point, I thought I was able to ping the external IP from another device sitting behind my T1 router, but I'm not sure this was ever the case). And yes, I had the firewalls configured to let pings through.
The only solution (and I was able to see this real time by watching my home server attempt to ping the Xserve's external IP) was to make Ethernet 2 the "primary interface". At this point, ping replies started coming back. I have no problem with this solution--I would just like to understand the reasoning behind it.
My theory is that the Xserve was trying to send replies out the local NAT'd interface (since it was primary) even though the initial ping message came from the secondary interface.
Background: my overall goal was to use multiple Xserves to distribute remotely accessible network services filtered through the firewall while still maintaining internal NAT'd interfaces so that the Xserves could be administered via the private, local subnet. DNS is setup so that the NAT'd subnet is a subdomain of the external domain.
Could somebody provide a little insight into this phenomenon so that more of us may better understand how things work?

... that ping reply still should have made it back to the source albeit routed through internal network first and out through the NAT gateway. Is this not the case?
No. Absolutely not.
Say your machine has two interfaces, a real-world IP 234.56.78.9 and a NAT'd address 192.168.1.2.
The NAT interface has a router address set to route through 192.168.1.1. The router has a public interface address of 65.43.2.1
Now, any outgoing traffic flowing through the NAT device gets NAT'd to the 65.43.2.1 address.
So here's the scenario. Remote user pings 234.56.78.9
Mac hears the ping and sends a reply via it's 192.168.1.2 to its default router.
Now, depending on the router make/model one of two things happen. Either:
1) the router is smart enough to realize that the ping reply is in response to a ping request it never saw and drops the packet (it won't send a reply packet to a query that never came in). or
2) the router NATs the traffic to 65.43.2.1 and sends the reply.
In the case of 2, the remote user gets a ping reply from a completely different address than it sent out - it pinged 234.56.78.9 and got a reply from 65.43.2.1
It quite rightly ignores the ping reply as being bogus. It doesn't know your internal network and doesn't expect to get a ping reply from a completely different address than it pinged in the first place.

Ethernet/IP: LV Loop Priority

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