Glitches on digital signal from 5751

I am driving four LMH6574MA multiplexers with digital signals from NI-5751 digitizer (running on NI PXI 7953R FlexRIO). There are glithches on all the digital signals (signal frequency is 40 MHz). Is there a way to clean these signals up in software?

Did you place the AI node in the IO Mod Clock 0 clock domain?
If you don't have those analog input nodes inside of the correct clock domain you'll be performing an unsafe clock crossing that will result in glitching.
The user manual walks you through how to add the IO Module Clock 0 to a project. Or you could start from the getting started example.
National Instruments
FlexRIO Product Support Engineer
Attachments:
CLIP help.PNG ‏32 KB

Similar Messages

Measure Frequency of Digital Signal from DAQ-Board

I'm using a National Instruments DAQ board and I need to measure the
frequency of a digital signal from my data acquisition board.
I know the measure frequency.vi (In diagram - data acquisition -
counter), but i don´t understand yours implementation mainly in input
"counter". Because i don't understand the relationship of board channel (for
signal acquiring ) and the measure frequency.vi.
Thanks in advance,
[email protected]

Hi,
Attached is a vi which models your signal, and provides a way to measure the average frequency over a window of time. It converts the signal to a sequence of periods. I usually start with this approach because you can save the data in a much more compact form if your sampling rate is high. Obviously over a specified period of time, if there are no zero crossings the frequency is zero, so I was a little incoherent before. The real issue is the latency caused by averaging. Your frequency measurement is most accurate half your window size before the current time, so smaller windows give you more up to date measurements, but also more noisy. If you need the most up to date measurement, then you have to use the time since the last crossing which is the case where the frequency never goes to zero. That's probably not a realistic situation. If you needed less latency, you could use a prediction algorithm.
Also, there are a number of signal measuring and processing vi's that LV gives you, for instance pulse measurements that could be used to partially implement this or other approaches, but I normally steer clear of them unless they fit exactly due to having to convert back and forth to the waveform data type.
Have fun!
Attachments:
DigRandFreq.png ‏62 KB
DigitalRandomFreq.vi ‏34 KB

How do I ouput a digital signal from an analogue signal

Hi all, I'm using a 6221 PCI card with LabVIEW 2010 (no add-ons) with the CB-68LPR connector block and I want to use an analogue voltage input signal of between 0 V and 5 V from an LDR to alter the brightness of an LED so I can maintain a stable level of illumination for a webcam based image capture and processing system.
I can get the analogue voltage input from the LDR (set up as a voltage divider circuit) using the DAQ assistant via the Ain 0 channel on using pins 68(AI.0), 67(AI GND) and 14(+5 V) and write it to a graph and numeric display but I don't know how to write the value out to a pin that can be used for PWM I am thinking of using pin 40 PFI 13 P2.5 and a digital GND (pin 13).
I've looked at example code that has been written to produce a PWM signal but these programs don't output the signal to a device/circuit they are just "nothing stuff" that output the PWM signal to a graph.
Can anyone help me out or point me to the tutorials/code examples that are for real world applications?
Solved!
Go to Solution.

Hello,
PWM can be done in DAQmx using a counter output task.
I think the 'PWM-Counter Output.vi' example goes quite a long way to doing want you want I think. This is found in the LabVIEW shipping examples.
I also found it here:
http://zone.ni.com/devzone/cda/epd/p/id/1710
This might be worth a read aswell:
http://zone.ni.com/devzone/cda/tut/p/id/2991
Let me know if this is of any help.
Nick C.
Cardiff University

Reading digita signal

I'm looking to write a simple program code that reads digital signal from the PXI-7350 that I'm using. Using LEDs to display the signal whether its high or low.
Just looking for someone to point me the way on how to do this. Thanks

Hi odsnot,
you can search in the Example Finder for "DAQmx". You will find a lot of useful examples.
Mike

Vb6,card: pci6111,daq box:bnc2110,receive digital signal+react on it,how?

want to send a digital signal from a function-generator into the daq-box (e.g. into ACH 2) and to react in my program on it, when the dig.signal makes the first step from 0 to 5 V e.g.must i change anything else on hw than connecting the function-generator to ACH 2? How can I react on it with my created CWDI1-Objekt. It doesn't work! Thnx a lot! p.s. other ideas are also wellcomed!

Hi,
I'm not understand the relationship between the components of your system (or even what they are!). You'll have to clear your system description a little bit.
1.- You have a DAQ board, what model?. This is important since it will determine what VIs you can use. Are you using the board for Analog input, anolog output ...?
2.- "The DAQ card relays the information to a digital oscilloscope", What do you mean by this?. Is the digital scope a hardware device or some sort of software component?.
3.- ActiveX is used to communicate different software components, not to communicate with external instruments. Again, what is the o-scope?.
4.- Initially you say that Win600 is a machine and then a program. Which one is it?.
I think once this quest
ions are cleared up we can start thinking of solutions.
DiegoF
National Instruments.

How to output the digital clock and synchronization signal from the NI USB-6211

Hello,
I need to connect the NI USB-6211 to control a digital to analog convertor chip (AD5541). However, this chip requires three input signals :1) Clock input, 2) Logic input or a synchronization signal and 3) Signal Serial Data input (CS, SCLK, DIN).
how to output the digital clock and the synchronization signal from the NI USB-6211?

Hi SaberSaber,
You should be able to use the counters to generate a pulse train that could be used for clock and synch purposes.
Hope this helps. Let us know if you have more questions.
Dave C.
Applications Engineer
National Instruments

My daq 6008 wil not drop the 5V after the VI is stopped, i have a digital signal going from the error out on the daq in the while loop to the error in on the daq outside the while loop and a boolean going to the data of the daq outside

my daq 6008 wil not drop the 5V on a digital output after the VI is stopped, i have a digital signal going from the error out on the daq in the while loop to the error in on the daq outside the while loop and a boolean going to the data of the daq outside, but i can t seemto get it to work

i attached the block diagram so you can have a look
Attachments:
PID Temp control.docx ‏120 KB

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

GB won't accept transposed MIDI signal from digital piano

For some reason I can’t get GB to accept transposed MIDI signals from my Previa PX-120 digital piano. The connections are correct, from the piano to my MacBook through an Edirol UA-25 interface, and the signal is getting through fine. If I want to record with the piano in default C, there’s no problem. But if I transpose at the piano, GB continues to play it through the monitor in C (the master track is set up to the correct transposed key). The signal coming from the piano is fine, as I’ve tested from the interface to speakers, and the same thing happens when I feed the signal through a Kurtzweil MicroPiano and do the transposition there - GB goes on reproducing it as default C.
The odd thing is that I had no problem with the same set-up with a Yamaha piano. This is probably irrelevant, but it’s strange.
Any help very gratefully received as this is screwing up recordings with piano, voice and guitar, when the piano player needs to transpose in some keys.

I’ve been asking myself the same question. The Privia manual is silent on the point and I can’t get a reply from their Support, though will try again. Unfortunately I’m no MIDI or sound technician, so know nothing about how transposed MIDI signals should work, but, having run tests again, the piano certainly seems to be sending an untransposed signal via MIDI. At least, when I connect the piano via MIDI to the MicroPiano the signal sent does not transpose (I was wrong in my first post about this), though I can then transpose it with the MicroPiano. This would be fine if all I wanted to do was then send it direct to speakers. But if I send the signal on to the Mac from the MicroPiano via MIDI, it doesn’t transpose either, and I’m back where I started.
In other words, neither the Privia nor the MicroPiano is outputting transposed MIDI signal, only default C signal, and this is the problem rather than GB. Does this make sense?
I’d be very interested to learn what you come up with re your Yamaha. I’ll get a colleague to try the same thing. And will also try Privia support again. But, meanwhile, if anyone else has any experience or knowledge, I’d really appreciate hearing.

Measuring digital signals coming from the HSDIO (PXI-6542) with the DMM (PXI-4070)

Hello,
in attachment you can find the program I'm using for my measurement: I'm generating and acquiring digital signals with the PXI-6542 and at some trigger point of one of those digital signals I'd like to capture the measured values on a plot with the Digital MultiMeter (PXI-4070).
It does work if you configure the generation repeat mode as continuous, but if you do have a finite repetition (repeat count is 1) it doesn't react on the trigger, as if it can't find a trigger. On the other hand, if you have a finite repeat count of 30 or more it does react and triggers correctly again.
First I though it had something to do with autocalibration before the measurement takes place, but If you do a highlight execution (stepping through the program) it looks like it measures before the generation session is initialized.
Is there a way to measure correctly when the repeat count is only 1?
Thanks in advance,
Jürgen

Hey Jürgen. I apologize that you haven't gotten an answer yet to your post. I looked at your code and had some questions. What is the source of your trigger to your DMM? I see that you're exporting the data active event to PFI1, and your comments indicate that PFI1 and PFI2 are connected to give you a start trigger for your digital acquisition. Exporting the data active event with a finite or continuous pulse should only give you a single edge per run, though - you wouldn't get a pulse each time. Is your trigger coming from a data line? I didn't see any line in your included data that would indicate a single pulse.
The other thing that I noticed is that you've got no timing dependency between your HSDIO code and your DMM code - they're in parallel with each other. Thus you could get different results run-to-run, since it's not deterministic as to which parallel "thread" that LV will start on first. LV may switch back and forth several times, but let's say that LV reaches the HSDIO Start command before reaching the DMM Start command - in that case, the HSDIO device may finish it's entire operation before the DMM ever starts looking for a trigger, and thus never get the trigger at all. I'm not sure why this would explain why you're seeing the finite case work and the continuous case not, but I wanted to point it out because it could bite you down the road.
I hope some of this this helps get you going in the right direction. I'd also suggest posting HW-centric questions in the appropriate form. There are Digital forums and DMM forums that might help you reach people that will be more familiar with your particular hardware.
Chris

Way to "downgrade" from digital signal on graphics cards?

Hello all,
I recently purchased an 8-core mac pro with the intention of using it for a lot of video installations for theatrical productions. I bought it with 4 of the Nvidia graphics cards, which are dvi and mini-displayport. These are both sending a digital signal, and it doesn't make it possible for me to use my DVI-composite adapter so I can plug into older TVs. I also have TONS of BNC cable that I can use to run cable paths, and this BNC has to have composite. This severely limits me, since my work involves grabbing whatever output monitor I can find. I've seen some posts on altering the signal with a EZ pc-tv converter box, but this is one more adapter/converter/whatever that can break during a performance. I'd like to just send it out from the source.
So my question is, is it possible to find a graphics card that still sends this analog signal, thereby allowing me to use my composite adapter? I just purchased the Mac Pro about a month ago, (just before they updated) and I wasn't sure if I could find anything like this. I've used the ez pc-tv box, but these don't appear to be too reliable, so if there isn't a way to install a graphics card, then is it possible to find a beefier conversion from the digital signal to analog so I can run long lengths of BNC cable?

The standard DVI connector also produces the five signals required for VGA signal on the same connector.
The DVI connector should have a solid bar toward one end of the connector. This is the ground for the four VGA pins (Red, Green, Blue, Horizontal Sync) that surround it. The fifth signal, Vertical Sync, is shared with the digital signal. A simple VGA-extractor has been available through the Apple store and other outlets.
A DVI to composite Video and S-Video adapter, which may have a few active components inside, has also been available. The one on the Apple Store lists only the X1900 for the Mac Pro, but it is not clear to me whether they have simply been lazy about updating the description.
The mini Display port adapters they list are
1) DVI-Digital-only (you can tell because the bar at the end lacks the four pins surrounding it) OR
2) VGA adapter (which you could convert to Composite with a component available in Europe they call a SKART chip).
Conversion of the digital signal is out of the question. You would need a screen buffer and as much logic as is already on the display card. Adapting the VGA signals is the way to go.

How to compare signals from two different .tdms files?

i'm developing a lie detection system in labview.so inorder for that i need to compare the threshold physiological signals from the .tdms file with the signals i acquire continuelsy from the subject for each question asked.i use respiration monitor and heart beat monitor together with the sensorDAQ to acuire the physiological signals.so which are the function i should make use of?i have the following toolkits
1. advanced signal processing toolkit
2. adaptive filter toolkit
3. digital filter design toolkit
4. biomedical toolkit
please give me advise on this.
thank you.
Solved!
Go to Solution.

Lie detector systems (polygraphs) generally work by looking at the physiological responses to the own subjects baseline, and do this in real-time. You could use a file that represents the stored "baseline" for the subject, but the overall environment, circumstances, general state of the subject, etc. may not be similar enough to easily see subtle changes.
From the stored file, you might determine a set of parameters or thresholds that indicate "normal, relaxed" for each signal. You could read the file into your LabVIEW program, process each channel, and save these parameters. Then when you have the new data, you can read the new data file in and process it in a similar way and then determine whether the parameters are outside the limits that you established for a "lie".
You may get more responses to this question if posted in the Biomedical User Group
Visit the NI Biomedical User Group at:
www.ni.com/biomedusers

How to input/output a digital signal and acquire an analog signal at the same time?

Dasylab, version: 8.0.04
Acquirement Card: PCI1002L
When I use DasyLab to acquire the analog signals is no problem without digital inputs and outputs,
and when I use DasyLab to input or output a digital signal is no problem also, but when I do that at the
same time, DasyLab tell me the rate is too high and stop.
so, I searched the manual book1 (user guide) for that, it showed me :
To internally equalize measurement time and system time in the analog input, digital input and counter
hardware modules, use the following settings:
   Synchronization: PC Clock
   Sampling rate: <= 5Hz
   Block size: =1
the problem is, if I set the Sampling rate to 5Hz, the speed of the acquirement datas is not enough for my
application.
so, how to improve it? who can give me a example programm for me. thanks!
by the way, I come from China, my English isn't good, I'm sorry.
Allen, China.

Hi,
Have things changed over the years?
I need to syncronise a digital output (Modul NI9474) and an analoge input (AI-Modul NI9203) module. I need to measure time intervals from a flank in signal A to a flank in signal B. I would like accuracies of the order of 1 ms. Currently, the signals are not synchronised, with errors of the order of 2 times the block length (block size x sample rate), sometimes much higher. The best I got so far was a block size of around 20 with a sample rate of 1 kHz.
If I use the master and slave settings on the RTSL settings, my program doesn't run properly.
If I use digital signals for input and output, I can syncronise them with RTSL settings and everything is good, but I can't always do that.
Also, if I do anything in the GUI (such as scrollowing something or going to another window), my output gets screwed up properly.
1. What can be done to synchronise AI with DO?
2. Is there something that can be done to avoid messing up the output when something happens in the user interface? (I know that I am messing up the outputs as they make some valves switch and that is loud).
Thanks in advance!

How do I convert analogue 5.1 surround sound into a digital signal? (Pioneer SE-DIR800C headphon

I understand that my SB Audigy 2 card will only output 5. sound from games through its 3 analogue connectors. How do I convert this analogue signal into a digital one? What hardware do I need to purchase?
I have read the thread on "Digital Connections, SPDIF and Dolby Digital Info", and also I've thoroughly read the "Creative Speaker Connectivity Guide".
The reason I ask is that I have just bought a pair of Pioneer SE-DIR800C Surround Sound headphones. This are supposedly fantastic for recreating surround sound on headphones because there is a clever little decoder box. They accept a DTS / Dolby Digital signal via the digital co-axial and optical inputs, and there is a single analogue input which only accepts stereo sound.
My XBox and PS2 will output true digital 5. sound via an optical cable and I am confident this will work perfectly with these headphones. I'm really looking forward to playing Halo in surround sound! But for gaming on my PC, I'll be limited to just an analogue stereo signal. Well, unless I can find some device that will convert my SoundBlaster's analogue 5. outputs into a digital signal, which I can then plug into the little decoder box for these headphones.
So, back to my question:
What hardware do I need to buy to convert an analogue 5. signal (via 6 x RCA or 3 x 3.5mm stereo ) into a true digital signal (via optical or co-axial SP/DIF)? Is it some type of headphone amplifier I need? If possible, please recommend makes & models of equipment.

Thanks stefan
OK, basically I have found 3 options for getting digital 5. out of a PC:
a) Creative DTS-60 (approx $90). This converts the SB's analogue into digital, but it's not available in the UK and it also introduces a noticeable 50ms sound delay. Also, who wants an extra box hanging out of their PC?
b) Buy a new sound card which has Dolby Digital Li've output. For example, ) BlueGears HDA X Mystique 7., or 2) Turtle Beach Montego DDL, or 3) Terratec Aureon 7. PCI (NOT the Space, FireWire or Uni'verse cards). I couldn't find the first two available in the UK so I have just ordered the Terratec card from Komplett.
c) Buy a new motherboard that has built-in Dolby Digital Li've output, for example the ABIT Fatalty AA8XE. Unfortunately my PC is only just over year old and I'm not quite ready to replace it.
I hope this info is useful for people. Maybe Creative will start making a card with DDL output too.Message Edited by NinjaHeretic on 2-22-2005 08:46 AM

How to check 6 digital signals change value at the same time with PCI-6229??

I am using DAQ card PCI-6229.
Channel 1 generate a digital signal.
Channel 2,3,4,5,6,7 acquire digital signals.
I want to check:
1. Whether the rising edge of Channel 2,3,4,5,6,7 occures at the same time;
2. The time delay from the rising edge of Channel 1 to the rising edge of Channel 2,3,4,5,6,7 is within a certain range.
I know I can use counter to get the two edge seperation time delay. But I only have two counter, it is two time-consuming if I check one by one.
I don't know how to check the rising edge of 6 different channels occure at the same time.
Does anyone has any suggestions?
Thanks

Hello,
You can use the DAQ card's digital input change detection circuitry to detect changes in the input, you can then use a counter to measure the relative time between samples. Please read Page 6-9 DI Change Detection Applications for more information. Let me know if this helps
Christian A
National Instruments
Applications Engineer

Glitches on digital signal from 5751

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