Comedi read command and acquire waveforms VIs

I am wondering about the implementation of the comedi read command in the VIs I got from the NI site.
One of the VIs is called "acquire waveforms" which calls "comedi read". everything seems to be working fine, but I am very curious about a small part of the comedi read VI.
If you look closely at it, you will see that after reading in the samples using the CIN that just calls read() , there is a formula node that basically asks the VI to save only the first half of the array. I am wondering why this would be so? Does it have to do with the way read() works?
I tried changing the VI so that the all bytes from the read() call are entered into the "data" array. But when I do this, labview gets stuck.
any ideas?

Hello:
This question belongs in the Measurement Hardware Driver Delvelopment Kit (DDK) Forum located here:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=8&RFORMNUMBER=3&RHIDETAG=TRUE&UCATEGORY_0=_321&UCATEGORY_S=0
The Comedi driver set is supported by www.comedi.org but you might get some answers from the DDK Forum as well.
Sincerely,
Brooks B
Applications Engineer

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VISA Read Timeout and VISA Write not working

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Attachments:
Triangle Volt Mod.vi ‏27 KB
GW Instek initialization.vi ‏18 KB

Yep, you need to append the End of Line character to the end of your command. And for your read to work properly, you need to request the data. That requires a querry command to be sent. Look closely at the differences in command and communication structures between your working VI and your mod.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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AI Acquire Waveforms High and Low Limit

Hey everybody,
I am currently working with Labview 7.1 and a daq card. I am collecting 4 channels and using ai acquire waveforms to do this. I want to have different high and low voltage limits for each channel though. Is there a way to do this with ai acquire waveforms or would can I use something else.
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Hey Devon,
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Sending commands and reading data - RS232

Hello guys !
I have a special problem communicatin through RS232 with a PIC microcontroller.
The problem :
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Attachments:
Serial-1.vi ‏53 KB

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[svn] 1978: Bug: vendors. properties file which is used in vendor specific login commands was not being read properly and as a result some login related error messages were not being displayed correctly .

Revision: 1978
Author: [email protected]
Date: 2008-06-06 08:05:34 -0700 (Fri, 06 Jun 2008)
Log Message:
Bug: vendors.properties file which is used in vendor specific login commands was not being read properly and as a result some login related error messages were not being displayed correctly.
QA: Yes - we need automated tests to make sure that errors.properties and vendors.properties in BlazeDS/LCDS are loaded properly.
Doc: No
Modified Paths:
blazeds/branches/3.0.x/modules/common/src/java/flex/messaging/util/PropertyStringResource Loader.java
blazeds/branches/3.0.x/modules/opt/src/jrun/flex/messaging/security/JRunLoginCommand.java
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I have a lot of grief with this version of Windows Media Player.
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I have some basic questions:
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Attachments:
TSS1-porem-final4.vi ‏16 KB

Thank you for suggestion!
Now I am receiving data continuosly.
1. As mentioned previously, I wish to plot the heave value on real time basis, I saw the shipping example, modified my VI.
The plot is not correct, as the heave value increases and decreases linearly but there is strange graph.
2. Also I have one more question, actually if I want to find out the heave value, device once moved up 10cm and brought back to 0 level again. Its not instant as the design of the device says it takes 2 secs to get back to the zero state again. The heave is read from 10, 9, 8,7 6, 5, etc. It takes 10 steps to come back to normal value, zero value.
I just need to plot the 0 and 10cm or may be next might be -5cm, I need to capture the final data. How can i do that?
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TSS1-porem-final4-1.vi ‏16 KB
MRU-TEST3-1.vi ‏20 KB

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Hello I am just starting to use the VISA read and write function in labVIEW
anybody knows what are the differene between VISA Read buffer and string? and comparison of VISA Write buffer and string
thanks
Solved!
Go to Solution.

Hi Ein,
"read buffer" is the label of the string given by VISARead, "write buffer" is the label of the string expected by VISAWrite!
So there is no difference...
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Error in acquiring waveform from the agilent 54621A oscilloscope .

error 1074003951 occurs when acquiring waveform from the agilent 54621A oscilloscope.
I have installed
agilent 546xx series instrument driver
NI VISA 14.0

The *IDN command is sent and i have chequed the VISA read it returns the correct string .The error still exists i have attached the block program
Attachments:
AGILENT 54621A Acquire Waveform.vi ‏16 KB

AI acquire waveform. vi update rate

Hello,
I would like to increase the update rate ( which governs how many samples are acquired per second) for the attached vi- AI Acquire Waveform(waveform).vi.
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If i type it manually, it doesnt stay and reverts back to 1000.
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poli
Solved!
Go to Solution.
Attachments:
AI Acquire Waveform (waveform).vi ‏14 KB

Hi Poli
Have you looked at the the daq examples. Labview is shipped with a lot of examples. Also are you running this by using the continuous run button? That button is for debugging only, and it is a no-no to use it for other purposes
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Hello
I have the following system: A Nanovoltmeter from Agilent, modell 34420A, LabVIEW 7.1 and XP as operative system on the computer. The voltmeter reads 1024 readings and store them in the internal memory. By using a command I can collect the readings via the GPIB or seriell port. I use the seriell port. Therefore I use the VISA routines in LabVIEW. I configure the seriell port, read the number of bytes at the port and finally read the data from the voltmeter. Everything works, except that I found out it doesn't collect all the readings. I tried using Waits between sending the command and reading the data. It doesn't help much. I tried then the VISA session in the NI-Measurement & Automation program. I couldn't collect all the data by just one Read command. I had to use at least two or three Read commands to collect all the data. I wonder, if I use the routine to get the number of bytes at the seriell port of the instrument shouldn't I get the whole number of readings stored in the instrument? I tried using a high fixed number, reading more data than available. I got more data but still not all 1024 readings.
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How to use AI acquire waveform.vi for continuous acquisition

Hello all,
I am using LabVIEW 5.1 and PCI-6023E to acquire a voltage signal continuously, display the acquired data on a chart(display one minute of data at a time)then save all the acquired data to a spreadsheet file.
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Attachments:
Acquire_Using_Random_Number.vi ‏89 KB
Continuous_Acquire.vi ‏96 KB

Helleo Labviewguru,
Yes, I did tried to see those examples but I could not display on a chart nor store to an array and save to a spreadsheet file when I used the AI Config.vi, AI Start.vi and the AI Read.vi(in a while loop). Can you please help me with this.
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Hao

Ai acquire waveform.vi

Hi,
Recently I receive a code from my senior to read data from DAQ bnc-2090. I have installed DAQmx 9.3 but I cannot run the code due to "cannot load ai acquire waveform.vi." I have find the answers that an old version of DAQ driver is needed. However, TDAQ driver is only suitable for Windows XP/2000, and I use Windows 7. What should I do to solve this problem? Thank you.

The only driver for that card is traditional DAQ and you've already found out that it is not supported on Windows 7 so why this question?

USB Camera and Low level VIs

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Hello TomBaum,
First, thanks for responding, really appreciate it.
Sorry that I cant send the Vi itself yet I have attached a picture of the part
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All I want to do is using USB camera instead of the one used now! so does
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Hope this can give you an idea.
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Attachments:
pic1.PNG ‏48 KB

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Acquire Multiple Waveforms(crosscorrelation).vi ‏77 KB

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How can I find an example about acquiring waveform data by software trigger using PXI 4070 DMM?

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hi there
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famous last words: "oh my god, it is full of stars!"

Comedi read command and acquire waveforms VIs

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