VISA to read/write COM1

Dear all,
This is a simple example to test VISA to read/write my COM1,
I have Labview 8.6 and even downloaded and installed the VISA441 again.
But it doesn’t read anything from COM1.
The error message is “timeout expired before operation
completed.”
I appreciate for your help.
Raymond
Attachments:
my visa write read.vi ‏8 KB

What are you communicating with? Are you sure you have the right kind of cable between the two. Between 2 PC's, you would need null modem cable. Between a PC and another device, you might need a straight through or null modem cable, you would have to check the manual for the device. Are you sure you have the correct communication settings? Usually you would need a small delay between the write command and the read command to give time for the other device to read the command and turn around and send back a response.
Do you know what the return message is supposed to look like? Does it need a termination character such as a line feed or CR/LF? How are you running this VI? It is set up as a one shot VI. Are you using the Run Continuously button to run it? I hope not.
You should really look at the examples in the Example Finder such as Basic Serial Write and Read.

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GPIB reads/writes compared with VISA reads/writes

Hello all,
Being slightly new to LV (3 months of casual use, and 1 month of really getting to know it)...
I was just wonder what the difference between VISA reads/writes and GPIB reads/writes.
Actually this is my main question: Is the GPIB Write "data" parameter and the VISA Write "write buffer" parameter the exact same thing?
Would I write the exact same command with either parameter and get essentially the same effect (if all parameters are correct?).
I have a list of GPIB commands that I want to use to write drivers for a PSA, and I really want to use VISA, and not have to change my paradigm of thinking.
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Thanks for your help.

The data you write with the GPIB functions is identical to the data you write with VISA. There are some things that are a bit easier to use the traditional GPIB calls but for 99+% of the time, VISA will do the trick. VISA was originally conceived as a common api for GPIB and VXI instruments. The first VXI instruments were basically the same GPIB instruments without a power supply and the user interface (buttons, screen, etc.) but they required different drivers. VISA permitted a single driver to be used for both types of instruments. Now, VISA has expanded to include serial, Ethernet, USB, and PXI and not having to change your "paradigm of thinking" is one of the big reasons that VISA is so widely used.

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We are using datasocket read and write functions to read and write shared variables programatically (in the same machine) but we only achieve a performance of aprox. 200 reads/writes per second. We are using Labview 8.6 with DSC.
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Hi MMCDAT,
I think this value can
be normal as you can see in this link:
http://zone.ni.com/devzone/cda/tut/p/id/5037
As you can see, the
limit for datasocket depends on your Ethernet limitations, even if you as using
it just in one PC:
http://digital.ni.com/public.nsf/websearch/6AC9E65734E53F9A8625672400637ECC?OpenDocument
You can improve the
performance changing the update mode or Vis configurations:
http://digital.ni.com/public.nsf/allkb/F8F7DE98856B50588625672400648045?OpenDocument
http://digital.ni.com/public.nsf/allkb/2D9C6D73A160537986256B290076456E?OpenDocument

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FP2010(A) need to transfer the measurement (from its I/O module) to FP2010(B) to do the data analysis.These data transfer should be synchronous btw two controller to prevent data lost.
From the vi used in the attachment,i encountered some problems at:
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All controller are communicating with each other directly without the need of a host computer to link them together
Is there any other method to do fast data transfer betwe
en controller?

Hi YongNei,
You were succesful in omiting enough information to make it very difficult to answer!
Please post your example.
Please tell us what version of LV-RT you are using.
Please define what you concider "fast data transfer".
Have you concidered mapping the FP tags of FP2010(A) to FP2010(B) and vise versa?
WHat exactly has to be syncronized?
If you have something that is close to working, share that.
Well, that as far as I can go with the info you have provided. Depending on the details, what you are asking could be anything from trivial to impossible with the currently available technology. I just can't say.
It would probably be a good idea to start over with a fresh question (sorry) because not many people are going to know what a a "
PF2010" is and I can not guarentee that I will be able to get back to you personally until next week-end.
Trying to help you get an answer,
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
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Urgent!!! Need help in file read/write data to a serial port

Hi,
I really need someone's help in order for me to complete my project. I have attached a vi which I have taken from an example and integrate to my project. In the vi, I have managed to get the encoder counts using Ni 9411. I need to read/write that data from ni9411 to ni9870 without using any serial port as they are connected to a NI 9104 chasis. May I know whether I am correct in writing the data to my ni9870 port using the vi I have attached? Does anyone know how i can convert the number of counts to a 8-bit data/byte so that I can send the data through the RS232 port? I really need someone's help as I need to finished in 2 weeks time.
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Attachments:
Encoder Position & Velocity (FPGA).vi ‏23 KB
SINGLEMOTORMODIFIED.vi ‏17 KB

Afai,
As I allready suggested you here, call your local NI Office and ask for assistance!
You really need assistence in a higher level that we can provide via the forums. Otherwise I don't see a chance for you to finish your project in time.
1. Convert I32 to U8 to write it to the 9870 could be done like this:
2. The vi to control the epos2.
There is NO way ( absolutely NO way) to port this vi to FPGA. It's based on VISA calls, uses an event-structure, both are not available at the FPGA.
The only thing you could do is to analyze the VI, the instruction set and design an FPGA vi which handles the specific instructions you would need.
I have no experience with epos2 and I'm not 100% sure if this would work as you would like to use it. And doing this needs deep knowledge of LabVIEW, VISA, Instrument Drivers, the epos hardware, FPGA programming, and so on...
Christian

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I attach the vis and the executables.
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Thanks in advanced!
Graci
Attachments:
Get_Value.vi ‏30 KB
Set_Value.vi ‏30 KB
Exe.zip ‏272 KB

Hello Bichillo,
By running the vis continuously you are running into race conditions. If you cannot control when you are writing to or reading from a global variable, you cannot know whether the value writen/read is the right one or not.
In your case the global variable value that is read is sometimes the last value writen and sometimes an empty string.
To make the global variable behave as desired, that is, keeping its last value, the global variable must be in memory when you access it using VI Server. If it is not in memory, the returned value is an empty string. That´s why you sometimes get a non-empty string: when you access the global variable to read its value, it happens to be in memory because you´ve just writen to it.
To ensure that the global
variable is always in memory and it keeps its last value, you must include the global variable into your block diagram. I am attaching modified vis that implement this.
Hope it helps.
César Verdejo
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Attachments:
Get-_Set_Value.llb ‏48 KB

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Never say "Oops." Always say "Ah, interesting!"
Attachments:
Read Spec.vi ‏110 KB
Write Spec.vi ‏58 KB

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Never say "Oops." Always say "Ah, interesting!"
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File Dialog.JPG ‏23 KB
Select The Required Test Spec.JPG ‏10 KB
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Scott Richardson
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Hello all! Rather new to using FPGA, but I have an interesting issue that's popping up.
Currently pulling in RAW voltage data from a set of sensors (Pressure Transducers, Load Cells, etc) through a cRIO DAQ. Have the FPGA file setup to pull in that data already and have the main VI and all the sub-VIs working just fine.
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Thanks!

Hi,
HySoR wrote:
The issue I'm having is when I use the FPGA Read/Write control to read in from the Target and save to the TDMS. When I only use a single FPGA target reference the lines are broken, but as soon as I switch to two targets, it now works.
Could you take a screenshot and post this part of your code? I'm having trouble understanding what you are describing.
Craig H. | CLA | Systems Engineer | National Instruments

How read/write matlab style WAV sound file?

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Thanks in advance.

That's a great help! Thanks. I have made the changes to the supplied NI VIs so that any rate can be used. The new read/write VIs are attached and seem to work ok.
Best,
F
Attachments:
Snd_Read_Wave_File.vi ‏128 KB
Snd_Write_Wave_File.vi ‏110 KB

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I'm newbie.
I try to program an application(digital image processing). And I want read/write an image from/to buffer (physic memory) or temp file. Is there any one can help ?
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Sorry about my English.

Hello Trung,
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Hi,
I am writing a waveform data into avi write in order to read back (with has data input on) as in example avi read write with data shipping example but the graph played back is missing some amount of data at regular intervals and hence the waveform read back is choppy.
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Thanks,

Can you post a VI(s) as I have trouble understanding what you are doing
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Different read/write VI's

Hello,
I notice that in labview, I can:
read/write to a SPREADSHEET
This requires FILE_PATH and FORMAT
read/write to a FILE
This requires a FILE_PATH and NO format
(because it is binary data)
I can read lines... BUT I CANNOT write lines
First question: why can I not write lines?
Continuing... there are other ways to read/write.
I can OPEN a file
And, then I can read/write
So: how is THIS read/write different from the ones above.
I can see that THIS read/write requires a refnum from the
open... OK... one structural difference...
This one does not allow for formatting... but yields a BROWN data.
Now, what is this DATA... is it binary?
What is the purpose of the OPEN/read/write/Close
on the second lines of the FIL
E/IO vi's
Can someone describe these and how they relate to each other?
Thanks,
Tom
Hello,

Tom Impelluso wrote:
> Hello,
>
> I notice that in labview, I can:
>
> read/write to a SPREADSHEET
> This requires FILE_PATH and FORMAT
>
This is called a TAB delimited file that most spreadsheet applications
can read
there is a TAB between columns and and EOL between rows. Writes in ASCII
(I should say ASCII printable since all chars are ASCII)
>
> read/write to a FILE
> This requires a FILE_PATH and NO format
> (because it is binary data)
Yep
>
>
> I can read lines... BUT I CANNOT write lines
>
> First question: why can I not write lines?
>
I found this strange also but, you can use the Write Char or generate
your own VI from
the lower level VIS. Which would be using the Write Char and adding EOL
as the last character in the line
There is a VI called Write + (String) that does not show up in the
palette but is used in some of the other VIs.
>
> Continuing... there are other ways to read/write.
>
> I can OPEN a file
>
> And, then I can read/write
>
> So: how is THIS read/write different from the ones above.
It is a byte stream which could be almost anything from ASCII to G
datatypes
>
>
> I can see that THIS read/write requires a refnum from the
> open... OK... one structural difference...
> This one does not allow for formatting... but yields a BROWN data.
>
> Now, what is this DATA... is it binary?
Not always but it can be. If you open an Excel file in a text editor you
will see
what a complex byte stream file looks like. The data is interspersed
with formatting bytes.
>
>
> What is the purpose of the OPEN/read/write/Close
> on the second lines of the FILE/IO vi's
these are the primitives that are used in all of the other file
functions.
This is the most basic level of what file I/O does.
>
>
> Can someone describe these and how they relate to each other?
The Open/Read/Write/Close are the primitves. The others are built up
from these
for special file types (like spreadsheet). They use the primitives and
add some formatting
and other options.
Dont reply to this e-mail address. My account is down and I am using
someone elses.
Kevin Kent

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i?
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Thanks...

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OK, I answered my own question. I knew that I could read from the FP-1600 via Datasocket reads using the Lookout protocol, but first attempts to write values this way failed. I made some seemingly insignificant changes to my vi, and now I am able to write values as well as read them. It would sure be nice to be able to use the FieldPoint vis to read data only when it changes, but I can live with the datasockets.
Rich

VISA to read/write COM1

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