How to playback a digital waveform

Hi I would like to do some post processing work on a digital graph data. I would like to use 2 seperate VIs for data acquisation and post processing. So first I acquire the data then pass the whole waveform data as an input to the other subVI but I olways get the last waveform . Could you please let me know how I can pass the whole information about a continous digital waveform without saving it on disk
thanks

You can do a variety of things, such as building an array of waveforms by auto-indexing them where you wire out of the aquisition loop. Alternatively, if you want just a single long waveform, the Append Waveforms.vi (Functions -> Programming -> Waveform -> Analog Waveform) should do nicely. You can also manipulate the waveform components directly and append the data arrays if you want some more control over it, but that's pretty much what the built in vi does.
The Colex Group
Lead Software Engineer
Certified LabVIEW Developer

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How plotting on a digital waveform graph the bit transition in function of the time

Hi everyone,
I am using LabView 6.1 on a Windows XP computer. I am to plot output bits sequences on a digital waveform graph just before sending the information to a board.
So far I can see the transitions for my 16-bit port (16 plots) but the width of a pulse is always identical, no matter what times I enter. I wired my 1-D array timestamps to the property node Xscale.MarkerVals[] of my digital waveform graph... but it doesn't seem to affect my plotting...
Thanks in advance for any help concerning this problem.
Jonathan Sabah

Well here is piece of my VI with the necessary sub VI.
I also want to hide/unhide plots... I have found how to hide.. but cannot figure out how to unhide.
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Jonathan
Attachments:
Exemple.vi ‏58 KB
Setup_DIO64_for_Output_1.0.vi ‏111 KB

How to do a digital waveform subtraction

i am trying to subtract two digital waveform using subtract operation, but it seems that the subtraction opertation doesn't like digital waveform.
error message:"You have connected two terminals with different types. the type of the source is digital waveform, the type of the sink is double"
anybody can help? please.

Hello,
See the attached modified example. Now you can access data in a 2D array .
Software developer
www.mcm-electronics.com
PS: Don't forget to rate a good anwser ; )
Currently using Labview 2011
PORTUGAL
Attachments:
dither tech2.vi ‏57 KB

How do I output three digital waveforms at once?

I posted this in Digital I/O, but now I think it's actually more appropriate here because it's not a hardware question. I need to output three digital waveforms at a relatively low frequency, 71.9 Hz. I have a PCI DAQ card, the 6024E and am using the NI-DAQmx functions to try to do this. My program basically generates the square wave that I want, and converts it into a digital wave. I do this 3 times for the three separate waves, and then I combine them into an array and send them to my DAQ functions, which are in a while loop so I can get continuous output. My problem is that the waveform that the DAQ is actually outputting is not what I want. It's outputting a wave that has the same duty cycle (approximately) but the frequency is over 2 kilohertz. It's not like this all the time; after it outputs about 7 cycles of this wave, it goes to logic low for a long time, and then repeats itself. When I probe the digital waveform right before it goes into the DAQ functions, it's running correctly at 71.9 Hertz. Am I doing anything wrong with the DAQ functions or the sampling information? Thanks in advance.
-- Josh Matloff

Hello Josh,
I'm pretty sure that the reason that your digital waveforms are not being produced at the correct frequency is because your digital output is not associated with any sort of timing. Unfortunately, with an E series board you can only do software timed digital operations. This means that the frequency at which the values on your digital lines will be updated depends on how fast/often your computer executes the DAQmx Write that is inside of your while loop. If you have an M series board, you can actually correlate the DIO operations with another subsytems clock (AI/AO sample clock, etc.) which means that you can acheive hardware-timed DIO. In the event that you do not have access to an M series board, I think that AnalogKid2DigitalMan was spot on that you would want to use counters to generate pulse trains (that is if your digital waveforms have a constant duty cycle and period). Depending on what the DAQ board is outputting to, you might also want to consider using the Analog Output channels to generate your digital waveform. As long as you continue to use the digital lines on the 6024E, there is not really a way to guarantee the timing of when the digital lines will be updated. You might be able to get close, but you will probably see some "hiccups", especially if your computer needs to service interrupts or give processing time to another application. And lastly, heed geckoee's advice and don't forget to properly close out your tasks! Putting in some error handling may also help in the debugging process.
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DE For Life!

How to send digital waveform to the DAC?

How to send digital waveform, obtained by Function Generator.vi to the Digital-Analog Converter? What kind of subVIs I have to use for this? I have LabView_5.0 on MacOS.

The 6032 is not a GPIB board. It is a DAQ board board and has 2 16-bit analog outputs, 8 16-bit outputs (16 single-ended), and 8 digital i/o lines. I don't know what you mean that a MIO16/LPM16 is connected to it. There are a lot of example VIs that ship with LabVIEW. Select Find Examples from the help menu and look under Hardware Input and Output. LabVIEW 7 has some under DAQmx>Analog Generation and older versions of LabVIEW have them under DAQ>Analog Output.

How do I sample a digital waveform?

I have a digital waveform that represents a 1-bit data stream. The bit rate is 1Mbit/s (i.e. For a value of '1' the line is high for 1us, for '0' the line is low for 1us).
I want to create a numeric array representation of the line by taking a sample of it every 1us and appending it into an array.
How do I set it up in LabVIEW to sample the line at 1MHz and create a 1-D numeric array of the bits?

Hi Raine,
It sounds like you're trying to keep data from previous samples in memory through the next iteration of the sampling loop, then append the new sample to the array.
Using shift registers is the most reasonable option. To create a shift register, wire your sample data to the edge of your sampling loop then right click and select Replace with Shift Register. You can then use a Build Array function to connect the shift register data with the current sampling data.
Cheers.
| Michael K | Project Manager | LabVIEW R&D | National Instruments |

How can you add comments to a text file while using a Digital Waveform vi?

Hi. I'm very new to Labview. I have a txt file of 1's and 0's wired to a "read from text file" which is then wired to a "spreadsheet string to digital.vi" ("digital waveform") and lastly to a graph. I want to add notes to the txt file that will not be read in the digital waveform. i.e. Like how you use // or /* in a C++ program to show that you are writing a comment and not code.
Labview version: 8.5
Thank you

You will just need in your text file a line at a time. Search the string for the characters // or /*. If it finds them, then loop back and read another line. If it doesn't find them, you must have a good line of data and you can pass on to the next part of your cod.

How to control individual channel of signal generated from digital waveform generator?

Digital waveform generator has 8 channels. I need to generate two different signals to HSDIO. How to modify and control two different channels? Also, how to translate pin outs from PXI-6541 to channels? I need to control signal into pin 1,3,29,and 31 individually.
Thank you!!
Solved!
Go to Solution.

You must combine your individual data into an array. The digital waveform is simply a digital representation of the binary array. It still boils down to bit 0 of each array element going to channel 0 (or the first channel you specify in Create Dynamic Channels). The next bit goes to the next channel. My last post is quite clear. To display the array in binary, right click on an array element, then select Display Format, then select Binary. You can also right click on the element, select Visible, then select Show Radix to display the small b before the number. One more thing, in the Display Format window, uncheck the box next to Use minimum field width. Then set the numeric just under the box to 8. Then select Pad with zeros on left in the box below.
You should not use waveforms until you learn more about how the HSDIO operates on input data. It isn't hard to combine waveforms, but it also isn't as clear as using an array of U8 or U16 or U32.
Trying to explain further. The first number to be writen to the HSDIO will have this effect: Bit 0 (LSB) of the number gets written to the first HSDIO channel you specify. Bit 7 goes to the 8th channel you specify. If you don't specify 8 channels, the bits get ignored. So wiring in one number will produce only one bit on each channel. In other words, the number already combines the bits of all the channels you specify. You don't combine anything yourself. Look again at my picture on my last post. By wiring in an array, you cause a bit pattern to be generated.
I hope this is more clear.
- tbob
Inventor of the WORM Global

Real-time - how to control speed of digital waveform

Deploying the VI attached to my RT desktop target I generate digital waveform on 8 channels on port0 and acquire data on AI [PXIe-6358].
The digital output frequency and analog input sample frequency are 10000 Hz therefore I expect that while one 8-bit digital code is active [valid] for 100us, one single analog sample is acquired. That means that I would expect one cycle of the while loop to finish in 100us x 2^8 = 100us x 256 = 25600us = 25.6ms.
However what happens is that the while loop finishes in 6ms regardless the set frequency. The loop finishes in 6ms even if I set 5/10/15kHz or if I put a 100us delay into the while loop. I also tried to set the source of the analog input sample clock to 'Dev/do/SampleClock' but nothing seemed to work so far.
How can I force the digital generation to be in correlation with the analog acquisition? I need to acquire 1 data point per channel while the respective digital code is active.
Thanks,
Krivan
Attachments:
RT_ai_dig_wave_gen.vi ‏56 KB

Hello krivan,
Thank you for your post on the forum.
Do you want the digital generation to start at the same time as the analog acquisition?
Shalini B
Applications Engineer
National Instruments UK & Ireland

How to split digital waveform channels?

Hi , could you please let me know how can I split the digital channels of a digital waveform(Let's say the digital waveform has 6 channels ) and graph them seperately.
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tintin_99 wrote:
Let's say I have acquired the digital signal at 1MS/s / Now I want to decimate the number of samples to 1kS/s. Again I know how to do it for analog signal using the decimate function. Do you know a way to do it on a digital signal?
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How to pass digital waveform to a raised cosine filter

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Coninued from here http://forums.ni.com/t5/LabVIEW/Please-any-help-would-be-appreciated-how-can-i-implement-a/m-p/30998...

How to get Digital waveform with Time.

Hi
I have 3 channels , each of which have ON/ OFF cycles specified with milliseconds as shown below.
Channel 1       OFF(3000) ON(2000) OFF(1000) ON(500) OFF(4000) ON(300)
                     The number in the bracket is the time in milliseconds for which the channel has to be ON or OFF.
Channel 2      OFF(800) ON(1000) OFF(6000) ON(2000) OFF(5000) ON(400)
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All the channels can be plotted in one graph or separate graphs.
I tried plotting with each OFF as False and ON as TRUE and built a boolean array. then converted to digital. but was not able to get the time (X-axis ) correctly. Is there any way to get Time on X axis for the Digital channel.
Thank you .Regards. Hema.

Hi Dennis,
I have done the same way as you suggested.but the sample rate is common to all the channels.( that is each channel is one boolean array column in the 2D boolean array which is fed to the Digital function , but i need separate sample rate for each channel(1-D array).
The Boolean array to digital takes 2D array as input, so i was not able to get different Time on X-axis.
But i found out a solution( very long method) by building time array separately and plotting the waveform without using sample rate.
Now i want to get rid of the '1' and '0' which gets displayed on the digital waveform by default . That is for every high there is number 1 shown and every low number 0 is shown on the graph. Please can I know how to remove this number display.
I saw digital waveform example too, but on all digital waveform, the numbers are shown. Is there any property to be set to disable 1 and zero display.
Thank you.

How do I graph more than 8 bits on the Digital Waveform Graph?

Greetings,
Does anyone know how have a Digital Waveform Graph that graphs Unsigned 16-bit numbers (rather than U8)?
Thanks

Just wire your array of U16 right to the bundler. The Digital Waveform Graph will just create 16 plots instead of 8.
Alliance Members are here to help. We do this stuff every day.
Daniel L. Press
PrimeTest Corp.
www.primetest.com

How can I programmatically detect transition times in a digital waveform

Hi, I have a digital waveform and at certain times I have transistions and glinches , how can I programmatically detect and record the time stamps of the transitions
Thanks

Let me see if I understand you. You are reading 14 bits in parallel and you want to know how long between transitions of just one of those bits - say bit 11. Is this bit number constant or can the number of the bit in which you are interested change?
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Mike...
Certified Professional Instructor
Certified LabVIEW Architect
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"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

Simultaneous analog and digital waveform read with PXIe-6361 and BNC2120 ?

Hi there,
I am trying to collect both analog and digital signals from a PXIe-6361 linked to a BNC2120, using the attached VI. I am running Labview 2011 64bit. This is the first time I am working with digital input. On the 2120 board, I have the digital input BNC cable connected to User Input 1 and wire between the screw terminal of UserInput 1 and the P0.1 (Digtial I/O) screw terminal.
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1) When I try to run the VI in its current state, I get the following error:
Error -89137 occurred at DAQmx Start Task.vi:3
Possible reason(s): Specified route cannot be satisfied, because it requires resources that are currently in use by another route.
Property: RefClk.Src
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Source Terminal: PXIe_Clk100
Required Resources in Use by
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Claire.
Attachments:
Export Waveforms To Spreadsheet File (1D)_wo extra line.vi ‏33 KB
Multi-Device Synch-Analog Input-Finite Acq-Analog Start_Claire_wDigitalin.vi ‏105 KB

Hi ClaireJ,
Sounds like a reference clock conflict. This KnowledgeBase (KB) talks about this error when using simultaneous sampling. Also, might want to check the device routes in Measurement and Automation Explorer (MAX) as discussed here. Finally, if you are routing your PFI line over a RTSI connection, this error can occur. This KB discusses it.
As to your second question, this post should help.
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How to playback a digital waveform

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