VISA READ STRING and GRAPH

I have some basic questions:
1. I have Serial communication from PXI to device. When I read the string of 26characters, continously, on Hypertermianl. It is fast enough. But when I read in the VI program, simple VISA read.
The reading is very slow. The VISA read one character at a time and take time to make a string of 26characters. Visa read is very slow, Why?
The baud rate is 1152K and rate is 32 updates per second, which is super fast in hyperterminal but very slow in Labview VI.
2. Second I need the extract the some data from my string at different positions on a string of 26 characters. I already made the subVI for reading it but since the VISA read is slow to read it gives wrong values from the string.
So I thought I can make an array and ask the subvi to read the the second (i.e n-1 value) 26 characters which are ready rather than first one which is being formed. But there is no arrays for string.How can I do that? also my concern is if I read n-1 value, it is not real time value.
:8 -0582                                n value Visa read slowly
:000000 -0076U 0008 -0582   n-1 value
:000000 -0074U 0008 -0582  n-2 value
:000000 -0075U 0008 -0582  n-3 value
3. I will extract the 74, 76, 77 etc say the value as AA. I want to plot the graph of value AA versus Seconds? How can generate Seconds on my X-axis?
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?
Attachments:
TSS1-porem-final4-1.vi ‏16 KB
MRU-TEST3-1.vi ‏20 KB

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Difference between VISA READ buffer and string

Hello I am just starting to use the VISA read and write function in labVIEW
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Go to Solution.

Hi Ein,
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Triangle Volt Mod.vi ‏27 KB
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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.
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I want to read the contents of a text file and print them to screen, but am having problems reading integers. The file contains employee's personal info and basically looks like this:
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To answer your question - I'm teaching myself java and I haven't covered enumeration classes yet.
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public static void readFile()throws IOException{
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How to read a C structure with string and int with a java server using sock

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Visa read object difference parity setting for PC and TPC2012 device

Hello,
we found some difference between application running in PC and runing in TPC2012 device.
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I just found out that the VI for the currentmeasurement with the keithley 6517a has the same error but still works fine. Now I also tried to adjust the serial data bit and parity settings via the VISA configure serial port function but still no improvements.

Xbee data extracting and graphing

Hi,
I have been trying for a few days to get this to work with no results. I have searched through google and some of the forums for help with nothing that really helped.
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The code is where I am not sure about. I was able to find examples of how to use the visa and was given a basic example of it. I have then tried to manipulate the program to see if ti would work for me. I am trying to take the signal from the VISA Read funciton and convert it to a 1d array to display on a graph. I have also tried to seperate the dat into an array char by char from the string. However, none of this worked. I am getting a zero value out for my graph and no values into my array. I am also getting no value into my READ String area.
The values I have sometimes gotten look like:
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The png is a pic of the results I got from the pulse input. So it looks like I am not getting any data at all.
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Attachments:
Basic VISA_Test_1.vi ‏26 KB
Result_OfpulseWave.png ‏129 KB

Hello jrod03,
I would suggest using the NI LabVIEW Interface for Arduino Toolkit found here (http://sine.ni.com/nips/cds/view/p/lang/en/nid/209835) and posting your Arduino related questions in our LabVIEW Interface for Arduino community (https://decibel.ni.com/content/groups/labview-interface-for-arduino).
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How to use multiple visa read in one program

hi
i am working at Hameg HM8143 power supply i want to measure voltage and current simultaneiously and use the measured values for further calculations. for this i used two visa read blocks.
>>>>>>the measured values are shown in the same visa read string however i want it to be shown sepetately,
>>>>>>One of the VISA read block gives error. so i want to know how to use VISA read to get current and voltage simultaneously in seperate strings
>>>>>>than how to convert strings to numbers for using them for my calcultions.
i am attaching screen shot as well
Attachments:
screenshot.JPG ‏164 KB

you can not use a single serial to send 2 commands simultaniously?
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Paul Falkenstein
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VISA Read function Read buffer problem in serial communication

Hi, I use VISA write and read function in serial communication app, the device continuously sends 0x00 if it is not receive a request from Labview program running on PC.
And the request sent by labview is programmable. I met a weird problem, each time the request changes, the VISA read buffer output port still shows the last request firstly, from second time, shows the right request.
It works like: Req code: ... 50, 51,51,51,50....; VISA Read buffer: ...50, 50, 51, 51, 51, 51, 50....
Please refer to the program.
Attachments:
readOne_test.vi ‏21 KB

How are you running this? You don't have a while loop around it. Is it part of a larger VI? Please don't tell me you are using the run continuously button.
You don't have any wait statement between you VISA Write and your bytes at port. So it is very likely the receive buffer is still empty since you didn't give your VI time to wait for the device to turn around and give a reply. If you read 0 bytes, your VISA read string will be empty. How does your decoder subVI (which you didn't include) handle an empty string?

Visa Read Overrun Problem

Dear all,
I am using VISA Read Function to read data coming from my Hardware.
The data is coming really fast. The H/W is sending 1600 bytes after every 10ms.
I am using Event Structure(timeout event) to check whether 1600 bytes are at port or not. Timeout is set to 1ms. i even tried with 0ms.
Baud Rate = 3000000.
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I have set the buffer size to 64000 but with no success. The problem still seems to persist.
i have played around with Receive buffer of COM Port in device manager. i tried all the values from 64 to 1600, again with no success.
every time i run the program i get an error stating,"A character was not read from the H/W before the next char arrived" at VISA Read Function.
and i am not doing anyother processing other than Reading data from the Port in the timeout event.
What could be the problem?
Thanks,
Ritesh

Ritesh,
The over-run is still caused by the driver of the hardware. What you are observing is that the driver is able to keep up with bursts of data coming into the port. So for the first few thousand bytes coming in, there is no error. However, after a while, the driver falls behind and cannot keep up (hence the over-run error).
How does FTDI recommend that you use their ports in LV? VISA may interact with the driver in a different way or set properties to different values. All of this can have an impact on how the driver performs. Also, this DLL that they provided may not return overrun errors the same way that VISA does. The malformed string may just be missing data that was missed because of an over-run error.
You have not mentioned anything about the types of flow control that are available to you. The only real way to prevent over-run errors in data intensive communication is to have ways to hold-off the data (flow control). Since the data will be interrupted for a fraction of a second, the driver will have a chance to get the data out of the hardware in time. Communication will automatically resume once the data is read out of the hardware.
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VISA Read over USB Problem: After a while the xBFFF0015 Timeout Error occurred

Hi,
I have trouble using labview with my non-NI USB device:
The device is an analog input DAQ board. I was able to setup communication with the board using a VISA driver specifically created for this board and direct FW calls using the product's firmware specification provided by the manufacturer.
This method has been working pretty good so far, but when I try to get large amount of data (64k samples @100ksps), the VISA Read returns the 'VISA: (Hex 0xBFFF0015) Timeout expired before operation completed.' error.
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First, an 'analog input scan start' command is sent to the DAQ device, and then the vi tries to read all collected data from the device, once the right amount of data retrieved, or no more data is available the data collecting process (the while loop) ends and an 'analog input scan stop' command is sent to the DAQ device.
The data collection starts with no problem, but after a while, in loop# 400, the VISA Read hangs and then returns the error mentioned above.
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Thanks,
John
Attachments:
usb-read.png ‏18 KB

I just wanted to specify that this is not an NI board avoiding to make people think this is a hardware issue. And I think that the rest of the code is irrelevant in this case.
I believe that I don't use the VISA functions correctly. I assumed that someone who used these functions before would be able to point out the obvious steps missing in the data collecting process using the VISA functions.

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Hi! I am trying to read string and numerical data from an xlsx file and trying to display its contents in a word file. I tried converting it to a .lvm file too. On using the "Read From Spreadsheet" tool, I get random characters as output. On using " Read From Measurement File" tool, I am getting an error saying "Error 100 occurred at Read From Measurement File->Untitled 1". What do I do? At the end I need to display the output, row by row, in a Microsoft Word file. I am so lost. Please Help.
Solved!
Go to Solution.

bsvare wrote:
labview currently does not read directly from an xlsx file. If you convert the xlsx to an xls file first, then you can use the read from spreadsheet tool to load the data from the file.
Hey, I tried doing that. It still just gave the values 0.00 in all the cells of the indicator array. Plus my file has string in it also. The data type in the spreadsheet was "general". Here in the tool, it is "Double". I changed the tool data type to string and spreadsheet to text but I only got gibbrish for my efforts.
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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.
I would hope they are quite similar. In fact, my research is telling me that GPIB is almost like a subset of VISA?
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.

How do I avoid Error 85 in Scan From String scanning VISA read buffer?

I have encountered an Error 85 with my Scan From String VI. I have a timed
loop to read data from a device (flowmeter) using a serial port. This device takes
periodic measurements and sends the reading which contains a numerical value to the serial port COM1. It cannot be read continuously, and the period
between measurements may vary, so I decided a timed loop would be better than a while loop.
The VI begins with VISA Configure Serial Port and then
goes to a VISA Write which sends the message to the device to begin
taking measurements. After this, the device usually says "TAKE FLOWMETER READINGS" to the terminal, thereafter only sending numbers. Then begins my timed loop containing VISA Read. I
am taking the read buffer two places.
First, I am taking it to an Array to Spreadsheet String with the
Format String %.3f, as was in the Write to Text File example. Then I am
using Concatenate Strings with this string and also a string containing
the System Time. This string goes to Write to Text File, which I have
configured using Open/Create/Replace File outside of the loop.
Second, I am taking the read buffer to a waveform chart. I thought
it would be a good idea to use Scan From String to convert the string
into a DBL which I am then sending to the waveform
chart.
I am not sure if the initial "TAKE READINGS" message is giving me an error. I was able to get one reading saved to my text file from the device.
Also the format string for my Scan From String is %.3f
I am getting the Error 85 at the Scan From String only sometimes.
When this happens, there is no data being written to the text file. But
other times, I get data and it writes to the text file just fine (but
rounds to nearest whole number).
Any help would be greatly appreciated! This serial port device has been giving me a lot of trouble.

Is this what you mean? Did I wire the shift registers correctly?
I didn't know if you meant to Concatenate before Scan From String or Concantenate before or after VISA Read?
Message Edited by YeungJohn on 11-20-2008 03:48 PM
Message Edited by YeungJohn on 11-20-2008 03:49 PM
Attachments:
SerialShiftVI.JPG ‏87 KB

VISA Read Losing Characters off the end of the output string

Hi,
So I am writing a VI to take an output string of data from an ardunio Uno and parsing it. I am using the Read Visa vi to grab the string from output of the device. In the end I will be connecting a device that actually gives value in this type of string format : (#80212164,2289,2292,2296,2300,2328,2289,2297,2290,2300,2308,2292,2295,2298,2289,22,24,0*).
So after a large number of loops, the program starts to drop the last few characters of the string that it outputs. So the string output from Visa Read will read something like (#80212164,2289,2292,2296,2300,2328,2289,2297,2290,2300,2308,2292,2295,2298,2289,22,24,). The only way to fix this problem after it has occured is to completely close labview (all the way). Once I open it again and start running the program, all is fine in the world.
Anyone ever have this issue? I have been trying to debug this in different ways and the only weird symptom that I have other than the Visa Read function losing a few characters of the string is the fact that looking at the Bytes at Port after I Visa Read, is that it starts showing five bytes instead of zero.
attached is my most recent attempt at solving this issue.
Note: The Ardunio outputs a string of this format every 2 seconds with the values being incrimental over a specified range.(#80212164,2289,2292,2296,2300,2328,2289,2297,2290,2300,2308,2292,2295,2298,2289,22,24,0*)
Solved!
Go to Solution.
Attachments:
Ardunio(StringOutput).vi ‏36 KB

So i did a long data collect and It looks like ever 43minutes and 24 seconds the system goes from cutting off the last 5 characters to not cutting off the last 4 characters.
As I cant see how Labview would be causing that, I am going to try and dig into the Ardunio and solve that issue... hopefully when thats done I can simplfy my code like you guys pointed out.
Thanks!
Attachments:
overnight_11_18.csv ‏3001 KB
Overnight.png ‏146 KB

VISA READ STRING and GRAPH

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