Retriggerable buffered counting edge task

Dear all,
I have been working on "Retriggerable buffered counting edge task" on a single counter input channel, let me describe what I want to achieve:
Create a CI to count finite rising edges with external sample clock (eg. Dev1/di/SampleClock) at certain sampling rate, and set CI.edge.Term at one PFI which is hardwired to another digital input channel. Furthermore, I'd like to set "retriggerable start trigger" to this CI by another PFI line.
It turns out that I can only set "arm start trigger" on this counter input channel, instead of "start trigger" since the error of 200452: attribute not supported in task context showed up at configuring digital edge start trigger. It seems that I can only set "retriggerable start trigger" on counter output task, and use two counters to achieve above, but I was wondering if there is a way to accomplish by single counter. Any suggestion is highly appreciated.
Solved!
Go to Solution.

Dear John,
I just tried and run into another issue with overflow. The idea is to synchronize this counter with finite DI and to read both buffers out when DI's buffer is filled. Since I am running CI in contineous mode, it seems to be reasonable to run into overflow on buffered CI after a couple of triggers; Error: -200279 when trying to read CI buffer. Is there a way to skip/ignore overflow but still read buffer with size that I specified at attribute of SamplePerChannel? or any better idea of design to achieve what I am trying to do? I was wondering how effective it would be by increasing buffer size to avoid overflow since no known pattern on the trigger signal.
Really appreciate your help. Thank you.

Similar Messages

Benchmarks for Buffered Counter Input with X-Series Devices

Hi,
Does anyone know the maximum transfer rate (using dma) for the x-series cards?
I'm looking for data simillar to the one in this link:
http://digital.ni.com/public.nsf/allkb/72A7E41EE5A8756A862571DA0076F1D7?OpenDocument
More specifically I want to know the transfer rate for the PCIe 6343.
Thank you,
Eyal
Solved!
Go to Solution.

I benchmarked 8MS/s on a single channel on a USB-6353 (should have similar performance to the USB-6356/66) with a buffered counter input task. This was only a 10 minute test on my Dell E6400 laptop ( Windows 7 32 bit, Dual core P8600, 4GB memory) so a sustained 24/7 rate is likely less. Also, I wasn't doing much with the data, just displaying it in an array. This is pretty much topping out USB streaming on this system (32MB/s) so I wouldn't expect to get higher. I wasn't running much else in the back ground (Explorer, Powerpoint, Lotus Notes) and CPU was at ~20%.
Hope this helps,
Andrew S
Getting Started with NI-DAQmx
Measurement Fundamentals

Retriggerable buffered event counting

I have been programming with Labview for the last 3 years, but know i have a problem:
Anybody know if is possible to do a retriggerable buffered event counting?
Thanks for your time.

Jofre,
Mark's suggestion is definitely a simpler and cleaner solution. I've done a pretty similar thing in the past with a 6602 and traditional NI-DAQ. I'd just add two more thoughts to go with his method:
1. You'll want to configure both the counters to be started by the same digital trigger signal so that their time information is synchronized, i.e., they both have the same "0" time.
2. You may need to watch for counter rollover, which occurs in less than a minute at 80 MHz. Not a real big deal, just a little thing to watch for when processing the data.
It could get a little trickier if your trigger signal is relatively rare (once or twice a minute or less). In such cases, you stand the risk of not knowing whether the counter rolled over between triggers or how many times. To help this problem, you could use a slower timebase (probably the 100 kHz) as a source for timestamping the triggers. There are other possibilties requiring the use of additional counters.
Other comments:
- Heed Mark's tip about group # if using Counter Config under traditional NI-DAQ.
- If you aren't heavily committed to traditional NI-DAQ, I'd suggest doing this with DAQmx. I admit that I struggled a while when making the switch but half of the effort was unlearning old ways. I've been using only DAQmx for all new development and I'd venture that for about 80-90% of the functions and features, I prefer it.
- (for academic interest only). It actually *is* possible to use the Z-index reload feature when configuring a counter for position/encoder measurement with a "two-pulse" encoder. You would simply hardwire one of the two inputs to digital ground, and configure the Z-index reload phase to "A LOW B LOW." There would still be two problems for the app in question here.
1. In encoder mode, the up pulse and down pulse must be signals wired to the counter's default SOURCE and AUX/UPDN pins respectively. You would need to somehow bring the internal 80 MHz timebase clock out to your terminal block pins. (I *think* but am not 100% sure that this can be done, but possibly only with DAQmx). Also, the reset signal must likewise be hardwired to the counter's default GATE pin.
2. The Z-index reload pulse seems to operate in a level-sensitive mode rather than edge-sensitive. As I recall from testing, if the trigger pulse remains in a HIGH state during several encoder pulses, the count keeps resetting after each one. One the other hand if it pulses briefly within the time that the A input is HIGH, no reset will occur. (Many industrial measurement encoders are designed to meet these Z-index requirements right out of the box.)
The more I think about it, the more I REALLY REALLY think there should be a setting that lets you reset a counter to a specific reload value on an EDGE of a software-defined GATE/TRIGGER signal.
Anyway, good luck with things.
-Kevin P.

How do I use the buffered counting mode at a fixed frequency?

Hi-
   I'm using a PCI-6259 M-series board with the Nidaq MX
drivers in Labview 7. I am trying to use one counter to do
buffered edge counting (eg. count how many pulses appear on one input
in 400 successive time bins of 10 uS each following a digital start
pulse). That is, my inputs are:
     Start Pulse (from experiment)
     Count Pulse (from a photomultiplier tube in the experiment)
And I want to know:
    # of pulses from 0 to 10 uS after the Start Pulse
    # of pulses from 11 to 20 uS after the Start
Pulse (or, equally good, # of pulses from 0 to 20 uS....I can
subtract later)
    # of pulses from 3991 to 4000 uS after the Start Pulse (or, # of pulses from 0 to 4000 uS...same thing)
   The Count Digital Events-Buffered-Finite-Ext Clk.vi sample
appears to do half of this. I can set this up CTR0 with the Count
pulse (and possibly add the start pulse as an Arm Start....I can't use
a Start Trigger, right?). However, I need to generate a Sample
Clock Source at 100 kHz (to trigger the card to buffer the counter
value and start counting in the next bin). So, I tried to set up
CTR1 along the lines of Gen Dig Pulse Train-Finite-Dig Start.vi for
generating a finite pulse train starting on a digital trigger, and
connecting the output from CTR1 to the Sample Clock Source on
CTR0. However, I get an error -50103 saying the specified
resource is reserved if I do both at the same time. But, I can't
see any resource conflicts...the pulse generation on CTR1 works fine
alone, as well as the buffered counting on CTR0, and all the PFI pins
are different. Is there some reason I can't use both counters at
the same time?
I think I can use the FREQOUT pin on the card to generate a Sample
Clock Source at 100 kHz, since I think this is independent of CTR0
& CTR1. However, I can't trigger the FREQOUT to always start
when I get a Start Pulse (as I can if I trigger a Digital Pulse Train
to start on a digital trigger...or can I?)...so my bins will move
randomly by up to 10 uS.
   This is an unrelated topic, but is there a discussion of
the relationship between the terminology in the manuals describing the
cards (SOURCE, GATE, OUTPUT terminals) and the terminology in NidaqMX
(Source Clock/SrcClk.Source, CI.CountEdges.Term, CO.Pulse.Term)?
Eg. is CTR0.GATE always the same thing as SrcClk.Source, or does it
depend on the mode of operation? If the M-series hardware manual
says to connect something to the SOURCE input, how do I assign an
alternate PFI pin to that SOURCE input in Labview? Does it depend
on the counter type, or is it always the same?

Dave,
Hi, you brought up several questions / issues -- let me see if I can help with some of them:
   I can set this up CTR0 with the Count pulse (and possibly add the start pulse as an Arm Start....I can't use a Start Trigger, right?).
Yes, you could set up this way. Also, as far as I know you're also correct that you need to configure for an "Arm Start" trigger using the DAQmx Trigger property node. The "Arm Start" trigger is used for counter input (measurement) apps while the regular "Start Trigger" can be used for counter output (pulse generation) tasks. I don't think I've experimented with recent versions of DAQmx though so it may have changed in 7.4 or 7.5
...I tried to set up CTR1 along the lines of Gen Dig Pulse Train-Finite-Dig Start.vi for generating a finite pulse train starting on a digital trigger, and connecting the output from CTR1 to the Sample Clock Source on CTR0. However, I get an error -50103 saying the specified resource is reserved if I do both at the same time
I highlighted the problem -- the FINITE pulse train. DAQmx uses CTR0 as a "helper" when you generate a finite pulse train on CTR1. It would generate a single pulse whose width corresponds to the exact amount of time needed for CTR1 to generate its specified # of pulses.
For your specific app, I think you could generate a triggered continuous pulse train with CTR1 -- this wouldn't need to use CTR0 as a helper.  The Start Pulse would arm CTR0 at the same instant that CTR1 is started.   If you set up CTR0 to acquire on the trailing edge of CTR1's pulses, then you'll get the time bins you want.
A final slight mod would be to setup CTR0 for measuring buffered periods (set units == "Ticks") instead of counting edges. In that mode, you wouldn't have to do the subtraction at the end.
   This is an unrelated topic, but is there a discussion of the relationship between the terminology in the manuals describing the cards (SOURCE, GATE, OUTPUT terminals) and the terminology in NidaqMX (Source Clock/SrcClk.Source, CI.CountEdges.Term, CO.Pulse.Term)? Eg. is CTR0.GATE always the same thing as SrcClk.Source, or does it depend on the mode of operation?
There's an NI app note and some discussion forum hits if you search the site for "daqmx terminology."
If the M-series hardware manual says to connect something to the SOURCE input, how do I assign an alternate PFI pin to that SOURCE input in Labview? Does it depend on the counter type, or is it always the same?
Usually, that choice would be available under the DAQmx Channel property node.   There'll be some place to define where the input signal is coming from, generally with "Term" or "Terminal" as part of its name.   Sorry I can't be more specific as I'm not at my LV computer now.
Happy counting!
-Kevin P.

Synchronize hardware timed buffered counter acquisition with buffered analog input acquisition

LV7.1
DAQmx
PCI-6036E
SC-2345
Windows 2000
Greetings.
I am simply trying to synchronize AI readings with readings from one Counter.
I am trying to perform buffered analog input synchronized with buffered counter acquisition.
I'd like the AI acquistion to trigger the Counter acquistion.
I'm currently setting the Sample Clock Source for the CI Cnt Edges Task to "Dev1/ai/SampleClock" but when I try and set the source for the "DAQmx Trigger" I can't seem to select one that works. I assumed that the source should be the "Dev1/ai/StartTrigger" but that produces and error as does selecting any of the PFI's.
I'm new to DAQmx and didn't have any luck with the examples or what's been previously posted.
Thanks for your help.
Attachments:
Initialization.jpg ‏84 KB

Gentlemen-
All of your initial help was great. I had some noise on my counter lines so switched from an E-Series card to a PCI-6259 M-series card in order to use the counter digital filters.
Now I can't get a corellated buffered counter and buffered analog input acquistion to work. This same code worked fine on an E-series card but it doesn't on the M-series.
I verified that the source and gate of the counter are working properly using the test panel and a external function generator.
But when I run the attached code I get no data out of the "Counter 1D U32 NSamples", only an error saying that the timeout of the function was reached and no count data became available. Am I missing the specification of a another clock or something?
The counters also work fine using the M-series example code "Count Digital Events (M-Series DAQmx) but this is not a buffered acquisition.
Any help would be greatly appreciated.
Steve
Attachments:
Sample_Code.jpg ‏136 KB

Buffered Counter Start/Stop

I am currently running an application requiring buffered counting
of high-speed events. I have a PC-6602, and I will be running three
groups of two counters each--one counter will run at 20 MHz for high
resolution timing, and the second counter in each group will count
rollovers of the fast counter to keep real time data. For neatness, I
would like to have three separate gruops of counters, but will they start
at the same time? I need all the counters to start simultaneously, and if
they are in different groups with different task ID's, how can I assure
they will all start at the same time?
Thanks,
Josh

Thanks for the response Filipe, I'll let you know how it goes. I only went into the header file because example code provided by NI ... paste ...
iStatus = GPCTR_Read_Buffer(iDevice, ulGpctrNum, ND_READ_MARK, ulReadOffset, ulNumPtsToRead, ulTimeOut, &ulNumPtsRead, pulReadBuf);
showed use of 8 parameters - in agreement with the header file and in disagreement with the on-line help file function documentation.
Tom

Buffered counter output in C

Hi everyone,
I am looking for a possibility to generate a finite buffered counter output with varying pulse widths, using the X-Series. I am working in C / Python.
I want to output two pulses triggered to an external signal. The first pulse should be short, the second pulse long.
The following code outputs only two identical pulses. How can I modify it to output two different pulses?
CreateCOPulseChanTicks(channel,"","100MhzTimebase",DAQmx_Val_Low,0,300,300)
CfgImplicitTiming(DAQmx_Val_FiniteSamps,2) #output two pulses
CfgDigEdgeStartTrig(src,DAQmx_Val_Falling) #external signal
SetStartTrigRetriggerable(True) #retrigger
Best Regards,
Stefan

It's good you found a workaround but the behavior doesn't seem right to me...
The default behavior in DAQmx (the C / LabVIEW / .NET APIs) is to regenerate data from the buffer. Perhaps the python wrapper you are using is disallowing regeneration somewhere? I tried this with regeneration disabled and it gives the same behavior you reported (though with regeneration enabled it does not).
You can use DAQmxGetWriteRegenMode to verify this theory and DAQmxSetWriteRegenMode to enable regeneration in case it is disabled.
Best Regards,
John Passiak

Display Count Of Tasks In Todo Task Group

Hello,
We've just completed a migration and created new outlook profiles for our users.
My director is certain that he used to have a count of the number of tasks in each group here:
Does anybody have any ideas as to how to get to this?
Any help much appreciated!

Hi,
Which version of Outlook did you use before? Is your director using any add-in to achieve the goal before?
As far as I know, Outlook doesn't have such feature to display count of tasks in To-Do List group. We can only show the count of items in each Outlook folder by right clicking the folder and selecting "Show total number of items" bullet.
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Steve Fan
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Buffered counting and 6602

Hello,
I am trying to run the vi 'Single Buffered Event Counting' using a
PCI6602 board. I have the vi set to use the internal timebase. It
seems to run , however it gets stuck in the While Loop. I don't
understand how the counter gets to be 'unarmed'. Perhaps there is
something I am missing. I also want to be able to write the data to a
file for later viewing. Has anyone written a vi to do this?
Thanks in advance,
Kristie Elam

Hi Jon,
I am trying to do some buffered counting and only read the data if a large number is available.
I attach a Labview version of what I am trying to do.
My program does not do anything means that the terminal count is never reached. If I remove this condition, I can actually read some data.
Thanks.
Attachments:
SingleTimeStamping_v8.vi ‏197 KB

Buffered counting 6008

Hi to all
Is here some one who can tell me how i can make a buffered counting of the pulse count
This make sure i have a correct speed count/time
The problem also is that i also need to see on meter how fast the speed is i want to count as fast as possible ,but the meter must run at normal slow speed
Sorry guys i am new to labview to please do not be so hard on me ,
Any one who could help me?
i want a TDMS file
Attachments:
snelheid wielen].vi ‏28 KB

mm
strange on page 6008 specs
http://sine.ni.com/nips/cds/view/p/lang/en/nid/14604
here its says
Buffered Operations
Yes
is counting not a operation?

Retriggerable gated counter or analog pulse trains

Hi all,
I have a problem I could not resolve in the last days. It might be even a question of creativity of how to come up with a solution.
I have an external pulse train 1 at ca. 8 kHz (frequency not fully stable). With this pulse train, I want to trigger with each pulse an analog waveform. Using X-series boards, this works perfectly.
But now I want to gate this analog signal with another pulse train 2 that is much slower than the other one (pausetrig option). Theoretically, this works nicely, too. But in reality, the analog signal simply ends at the point where it is stopped by the pause trigger, whereas I want it to stop at the end point of the waveform.
Please have a look at the drawing attached
I would be really glad about any ideas on how to solve this problem.
Best regards,
Peter

I don't think I've ever defined both a start trigger and a pause trigger defined for the same task. Good to know it's allowed.
Given what you've already found, the solution is to control the timing of the end of the pause trigger pulse's active state (shown here as high).
Here's one approach:
1. Create the pause trigger pulse with a retriggerable single pulse task. Use a minimal "low time" and "initial delay". Set the high (active) time to be approximately (N+1) periods of your AO sample clock.  Technically, N+1 periods is a bit more than necessary, but it's sure to be enough and doesn't require research into deep details of AO timing.
2. Configure the AO task to use the pulse as *both* its start trigger (rising edge) and its pause trigger (pause when low).
Comments: this makes for a different timing diagram than you've drawn. Each external 8 kHz pulse causes a minimally-delayed pause trigger pulse which lasts long enough to generate the full AO waveform but ends before the next 8 kHz pulse. The choice of when to start and stop this trigger pulse will be up to your own logic and will be governed by software timing.
   Oh dang! That still leaves you susceptible to a partial waveform since you can't sync the software timing to occur during the desired small fraction of the 8 kHz interval with no AO waveform.
Second approach:
1. Similar to #1 above, but set the high (active) time to cover multiple 8 kHz periods and *don't* make the task retriggerable. To get the timing right in hardware, you'll need to generate a pulse that's *approximately* the requested length, but you'll reserve the right to tweak it so the edges fall in the right place.   You'll also define your pulse in terms of the external 8 kHz signal rather than in terms of internal board time.
     Specifically, configure to generate a pulse based on units of "Ticks" using the rising edges of the external 8 kHz signal as the "source of ticks." Set a minimal value (probably 2) for both the "low ticks" and "initial delay" inputs. The "high ticks" setting is where you do your tweaking.
    Suppose the desired pause trigger time is 10.3 msec. Nominally, that's 82.4 intervals of the 8 kHz external signal. Well, just round up or down as you see fit and wire this integer # into the "high ticks" input.
2. AO task is configured to retrigger off the external 8 kHz signal and be pause triggered by #1's counter pulse.
Comments: When you start the pause trigger pulse task, it will remain in its low idle state for the first two 8 kHz pulses. It will go high on the 3rd pulse and then revert low on the 82nd subsequent pulse.
   Because this pulse *also* acts as a pause trigger for the AO task, you're now synced such that the AO task is paused exactly as it is being retriggered, meaning that the previous waveform must have been allowed to complete. (The deep details of timing will prevent the AO task from generating 1 sample at this instant.)
-Kevin P

Is it possible to use "Delay Values" to create a frequency signal from digital "Count Edges" -task? (= are the results I'm getting correct?)

Hello.
I have a digital encoder from which I need freaquency information (to ultimately get rpm -infromation). The problem is that this task is inside a loop with 2 other DAQmx -tasks that are using "one sample on demand"-aquisition mode and if I configure this new counter task to be a freaquency task, it only updates once in ~ second which makes the whole loop lag.
I thus created an "artificial" freaquency signal by using "Count Edges" -aquicition mode and the "Delay Values" -block so that I substract the delayed signal from original "Count Edges" -signal. There is a 0,01s delay in the loop and I figured out that if the history of the "Delay Values" -block is 100 samples I would thus get the real edge-freaquency.
I tested this configuration and the results seem to be at least really close to correct but I have no idea if this idea is in any way correct...
This explanation was probably quite confusing so please see the picture attached.
Thanks a lot in advance!
Attachments:
are_the_results_correct.jpg ‏200 KB

First of all, thank you for quick reply. Unfortunately I don't have the acces to the vi. until tomorrow.
And yes, I think you understood correctly: essentially this arragement measures how many edges have been counted during one iteration. This is how I figured out that this could then be used as a frequency measurement:
1. From the "Edges - Delayed Edges" I get the information on how many edges have been counted during last iteration.
2. I "know" (really I don't?) that one iteration lasts ~0,01s because of the delay in the loop.
3. There is 2048 edges in one round of the encoder so I get the rpm as follows: rpm = (edges - delayed edges)/204,8*60(s)
(If I was using history size of one as you suggested it would be: rpm = (edges-delayed edges)/2048 * 60) However using history size of 10 and taking it account in the multiplication smoothens the response nicely.
But doesn't this arragement count on the fact that the vi runs smoothly and there is no additional lag?
I quess using another loop and notifiers for a dedicated freaquency measurement as you suggested could be worth trying. I just have to first learn how to use them.
If I do use them will the main loop run smoothly and not wait for every update of the notifier? This would be essential since the freaquency output refresses only about once in a second if I use the continious aquisition mode.
Attachments:
are_the_results_correct.jpg ‏198 KB

A simple count egdes task

Hello,
I have a simple little Question. My Problem is that the counter counts to many events if the second counter signal is connect. But first I will tell you what have I done. I create a simple egde count Task with MAX. MAX Tells me to connect my encoder signal to PFI 3. If I do this all is okay. But if i connect the second phase shifted encoder signal to PFI 5 (I need this for a another task) the counter counts two times more egdes as it should be. Is this okay? What have I made wrong? Is there a possibilty to avoid this?.
Thanks for your help
Best regards
Stefan Farmbauer

Hi Stefan,
first of all, I need more information about your setup:
1. What NI device are you using (device number, E-Series or M-Series,...)?
2. What's the Version of your DAQmx driver (check out My System >> Software in MAX)?
3. What's the Version of your MAX?
4. Which counters did you specify for your tasks?
5. How did you configure your counter tasks (edge count, rising/falling,...)?
6. Which terminal block (to connect your device to the quadratur encoder) are you using?
7. Which Pins on the terminal block did you select (did you choose the right ones)?
Please answer the above questions, so I can be of assistance.
Bye
Daniel
NIG

Can buffered digital edge detection only be performed using an external sample clock?

I am working on an application where I need to measure the speed (rpm) of a motor as it starts up using the output of its built in hall effect sensor. The sensor should output 2 pulses per revolution of the motor. My plan is to count the pulses from when the counter (counter 1) is armed to when it is up to speed. Looking at the M series manual, the CVI (v8.5.1) help, and the examples it appears that this can only be done using an external sample clock. Is there a way to route an internal sample clock to the appropriate terminal on the counter so that I do not need to add additional hardware?
I am currently using a PCI-6289, but the final application will use a CDaq-9188 chassis (using one of the the built in 32-bit counters).
Thank you for your assistance.

Thank you for your input.
However, I did forget to mention one detail of the application. I need to buffer the edge counts so that I can graph the speed of the motor as it starts up. I need to be able to acquire the edge counts at reqular intervals so that I can determine how fast the motor was rotating at each point. So far I have not been able to find an example of doing this without and external sample clock. As I mentioned, in the final application I will be using the 32-bit counters on a CDAQ-9188 chassis. The only thing I can think of at this point is to generate a pulse out of the second counter and use that as the sample clock. Will this work?

Buffered counting labVIEW 5.0

I try to use the measure buffered period.vi with labVIEW 5.0 and my NI-TIO device is the 6601. The problem is that: I can find the vis used to run the measure buffered period.vi. i.e. Counter group config.vi, counter get attribute.vi .......

Augerspecto,
I am assuming that you are referring to the Measure Buffered Period.vi example included with LabVIEW. If the example is not finding the counter VIs when it is loading you probably need to check your NI-DAQ installation. Ensure that you have NI-DAQ installed and if you don't, you need to download it and install it for those VIs to be available (http://digital.ni.com/softlib.nsf/MainPage?ReadForm&node=132010_US). If you already have NI-DAQ installed then check to see if you have the VIs on your Functions Palette (Functions > NI Measurements > Data Acquisition > Counter). If you don't have the VIs on your palette then reinstall NI-DAQ and ensure that you install support for your version of LabVIEW.
Ames
Applications Engineering
National Instrumen
ts

Retriggerable buffered counting edge task

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