Array to String (VISA Write)

Hello all, I'm trying to use the function "Triangle Wave.vi" from the Owning Palette "Signal Generation VIs" to output a triangle wave pattern voltage to an external DC power source. My power source is an RS-232 connection, therefore I'm using VISA Write to write the triangle pattern voltages to the power source. The problem is that I have to:
1) Write the voltage to a string input for VISA Write (syntax: :CHAN1:VOLT\s__, where the blank is where the voltage we want to write to the instrument goes). The output for the Triangle Wave VI is an array of doubles. How do I extract each voltage value from the array of DBL?
2) How do I take those single voltage values and write them into a prewritten string? I'm assuming we'll use concatenate strings for part 2.

I appreciate the feedback. I implemented your suggestions, but it still isn't working. I can't figure out why it won't work. When I turn on execution highlighting, the error seems to occur at the actual Triangle Wave VI, because the number it shows as the output from the triangle wave VI is nonsense (although at first I assumed this is because it is outputting an array that hasn't been parsed yet). I added 15 to the output of the Triangle Wave VI which I thought would work, since arrays are polymorphic. However, the number that the program sets to the power supply is 15 over and over again. I am including the (nearly) completed VI.
Attachments:
Triangle Volt Mod.vi ‏19 KB

Similar Messages

How do I write an array of strings to a single Excel row?

I'd like to write test data, as an array of strings, to an Excel file. Attached is my attempt to modify one of the Labview 6.1 example files. This modified example will write the data to the correct row, which is determined by serial # of the UUT, but to a new sheet for each unit. I'd like to do the same thing, but to just one sheet. This sheet's data would then be saved after 50 rows of collected test data.
Thank you in advance,
Tim Denson
Attachments:
Write Table To XL.vi ‏58 KB

Sorry I didn't get back to faster on this. I've been out of town working and just really haven't had time.
Yes,
The Report Generation toolkit would make this very easy. If you have it, I'd suggest using it.
The image shown below shows the five VIs from the toolkit that I've used to write to Excel.
What this loop does is receive a string through a Queue, either open a
template or open todays file, convert the tab delimited string to an
array, write the array to the next line of the Excel file, Save (with
todays date stamp if opened from the tempate) and close it. It's a good
idea to always save and close teh file after each write if it's not
being continuously written to. In this case, a new line will be written
only once a minute or so. This lessens the chance of losing data if the
machine locks up for some reason. Opening and closing does take time
and can slow down a loop that needs to run at a certain rate. This loop
actually runs in a background process and several other processes send
data to it through the queue to be written. The queue can buffer
several data streams if needed so you won't lose data if it's busy and
you don't have to worry about two processes accessing the Excel sheet
at the same time.
Ed
Message Edited by Ed Dickens on 02-18-2006 11:12 AM
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.
Attachments:
RGTK Array to Excel.gif ‏14 KB

How can i write a sign string in VISA Write?

Hello everybody.
I would like someone to help me. I have an
array, which is transformed (by Byte Array to String) in a string that
reaches the VISA Write Serial Port. My problem is that when making the
transformation with Byte Array to String, i lose all the bytes with sign
(negative).
What can I do? I don't want to lose the sign bytes and be able to send them to VISA Write Serial Port.
Thank you very much.

It sounds like you have a typecasting problem. First, why do some of your bytes have a sign? I assume they are I8. Strings are based on U8 because they are just a series of ASCII characters vs. values. The ASCII character table goes from 0 to 255.
What happens on the other end of the VISA communication string?
One thing you could do is to typecast your bytes to a U8. Though I think the coercion dot of an I8 byte array going into the byte array to string is doing this automatically.

How can I send multiple string commands into a VISA write?

Hi Fellow LabVIEW users
I am very new to LabVIEW (2.5 months) so please forgive me if my lingo is not up to par.
How can I send multiple string commands to a VISA write. For example each string command looks like this
1) 3A00 0000 0000 FFFF FFFF FFFF 0000 0000 FF00 0000 0000 0000 0000 0033 (Scenario 1)
2) 3A01 0000 0000 FFFF FFFF FFFF 0000 0000 FF00 0000 0000 0000 0000 0034 (Scenario 2)
3) 3A01 0000 0000 33FF FFFF FFFF 0000 0000 FF00 0000 0000 0000 0000 0067 (Scenario 3).
and so on and so forth. And there are a number of scenarios.
Each String scenario will give a different string output which will be interpreted differently in the front panel.
Right now I have to manually change the string commands on the front panel to give me the desired output. How can I do this without manually changing the commands i.e. hard coding each scenario into the block diagram?
Thanks, any feedback will help.
mhaque

Please stick to your original post.

How do I input multiple string constants into VISA Write

I am trying to put in multiple string commands into VISA Write to control a motor arm. However, when I use "concatenate strings" to link together my multiple string constants, only the first command is executed, and neglects the other commands below it. Should I be using something other then "concatenate strings" or do I need to use a delay so that the next command executes when the one before it is finished? Help.

Concatenate strings should work or just use one string constant with multiple lines. The problem you're having could be that the instrument requires some sort of delay but without details on the instrument, only you or the vendor can answer that. Some instruments will have a queue and others won't. The other possiblity is that you need some kind of termination character between commands. This might be a carriage return for a serial instrument or the ; character for a GPIB one. Check the instrument manual or provide the make and model and maybe someone here has some experience with it.

Can I write arrays of strings to OPC server?

I am using shared variables for their built-in OPC server functionality. I have configured some of my SVs as strings, as arrays of doubles, as arrays of booleans, and as arrays of strings. When I connect to the NI shared variable engine using the MatrikonOPC Explorer OPC client application (a free app recommended for OPC troubleshooting on the NI website), I see data for all of the shared variables EXCEPT the SVs that happen to be arrays of strings, which show no values and a quality of "Uncertain, non-specific". If I use DataSocket to connect to the same SVs using their OPC URL, I see the same quality result (Quality=64). Is there something I need to do to ensure that SVs configured as arrays of strings work properly as OPC tags? (string lengths?, termination characters? etc). In MatrikonOPC "Array of Strings" is listed as a possible Data Type, so I assume that what I'm trying to do is not impossible. The reason I'm trying to have OPC tags as arrays of strings is because my system has a variable number of channels, and I want to transmit the channel name list to an OPC client. Does anyone have experience with this?
NI Software : LabVIEW version 8.6.1
OS : Windows XP

I've downloaded a couple of free OPC client apps (MatrikonOPC and CAS OPC) and they both seem to list an array of strings as a possible data type, though I can't say if that is a commonly implemented one or not.
You are correct that I would like the LabVIEW shared variable engine to act as an OPC server in my application. Data will be acquired on the PC running LabVIEW, and written to OPC tags for sharing with another PC on the network. I'm actually not positive what the client application will be, since it will be supplied by the customer that is purchasing the software. It might be Wonderware, but I'm not 100% on that.
If I am unable to solve this problem then I guess I can always create a separate SV/OPC tag for each DAQ channel and pass data that way, rather than my current method of creating only two SVs: one that is an array of channel names (strings), and one that is an array of channel values (doubles). It just seems a bit inefficient to create a whole bunch of OPC tags that may or may not be used, since the number of channels enabled and their names will all be based on a user-supplied configuration that may change from one run to the next. I'm not much of an OPC expert though, perhaps creating a whole mess of OPC tags is the normal methodology that people use.

How to convert a dynamic data type to array of strings

I want to perform a serial communication between two
computers that I´ll call them A and B. The computer A (transmitter)
will send a signal (sinusoidal) to computer B (receiver). I´m using a
VISA Serial Communications Set (VISA Configure Serial Port.vi, VISA
Write.vi, VISA Read.vi and VISA Close.vi). VISA Write accepts
only string data type and VISA Read reads only string data type, but
the signal that I generated (on transmitter) is dynamic data and I need
to perform this conversion to run my program sucessfully. How can I
perform this conversion?!

Hi Rafael,
You can configure the From DDT Express VI to convert your dynamic data to any number of different types. By default, the Express VI will convert to a 1D array of numerics...however, you can configure it (either when you first drop it, or by double-clicking it) to convert to a 2D array of numerics...additionally, you can configure it to convert based on channel data being in columns or rows. I have attached another screenshot that shows converting the dynamic data into a 2D numeric array.
I hope this helps.
-D
Darren Nattinger, CLA
LabVIEW Artisan and Nugget Penman
Attachments:
FromDDT2D.jpg ‏164 KB

Make visa write return sooner

This is somewhat a continuation from this thread but I figured it was different enough to warrant another one. My question is this: I have multiple visa (serial) references in an array. I use an autoindexing for loop to write to each one. I have benchmarked the VISA write function and it takes 14 ms to execute when writing 68 bytes of data with a 38,400 baud rate. Because I have them in a for loop if I am using 8 serial ports, it takes over 100 ms for the for loop to complete. By this time, the hardware has expected another write to have happened on the first serial port, but because the subsequent writes (which are in serial..ha..ha.) take so long to execute, it hasn't written again. I know one solution is to put them in parallel, but I am trying to avoid spawning off threads on a PXI chassis based on the number of serial connections I have. This not only complicates the serial communication, but greatly complicates my application because then I would need to manage a dynamic number of queues being used to pass data to my host communication thread.
As a side note, I have tried both synchronous and asych writes.
Is their any way to communicate via serial, maybe on a lower level than visa, so it just sticks the data in a transmit buffer and leaves it there for the hardware to manage, rather than waiting for what looks to be a return after the data has been sent.
CLA, LabVIEW Versions 2010-2013

Jeff Bohrer wrote:
Well, the async writes should be about as fast as you can go. but the math (14mS for 68 bytes at 38400 Baud) seems off. How are you connected to the PXI device. I'm thinking a chassis controller might have less latency than say a MXI bridge. You aren't doining anything silly like re-initing the VISA session right? Put a conditional probe on the session in- is it valid?
Currently I'm not sure how I am connected. However, I can say that no, I am not opening and closing the session in the loop. I made a test program that is just visa open, loop with visa writes, then visa close outside the loop. I have also verified the string truly is 68 bytes and there aren't extra characters in there I'm missing, or something like that.
I have connected a scope up to the serial line. I put a gap of a few ms between writes so I can see where one transmission ends and the next one starts when looking at the scope. If I (on the scope) measure the delta time between the start and end of the transmission, it's ~19.4 ms. If I calculate 68 bytes*8 bits/byte + 3 bits for start stop parity / 38400 baud I get .0142 seconds or 14.2 ms. Is this calculation correct? The result is very close to what my benchmarking of the Visa Write is showing. Also, I'm curious of the 5 ms discrepancy between the delta t on the scope and the visa function time to execute. Any more thoughts?
CLA, LabVIEW Versions 2010-2013

VISA Write hangs after running OK for a while

VISA Write function (VISA abc W) in my VI runs OK, with a Return Count of 4, for a while (100's to 1000's of times) then it hangs. The Return Count from this function is then 0. The Error In and Error Out show no errors. Clicking HIGHLIGHT EXECUTION shows the output wires from the VISA Write as colored grey, while everything else has normal color.
Clicking the VI red ABORT button, or any of the sub VIs red ABORT buttons, fails to abort or reset the VI even after 20 minutes. Task Manager will stop LabVIEW, but then LabVIEW will not start up again without shutting down and restarting the computer. Changing to a different Windows XP computer and a different PCI-GPIB, NI-488.2 board, as well as reinstalling LabVIEW 7.0, or using a different LabVIEW 7.0 serial number, has not solved the problem.
Thank you for your help.

Thanks for your reply. Attached is a PowerPoint file that shows info on our computer and LabView, and a For Loop
(Slide 3) that runs the VIs addressing one of our instruments (Hart 1590 Super Thermometer). Slide 4 shows the
block diagram that is pretty much as downloaded from National Instruments. The block diagrams for each of the
colored sub VIs contains a sub VI having a VISA abc W function as shown in Slide 5. The only places this VISA
function hangs is in inside the While Loop, inside the yellow Meas. Status. VI or the blue Read Meas. VI. The
Meas. Status. VI sends "new", and the Read Meas. VI sends "tem" to the Hart instrument.
Also attaced are the VIs for the Measurement Status and the Read Measurement. In the course of trying to fix this
problem I've added various time delays of 50, 100 msec, up to 1 sec, thinking that the Hart needed more time to
respond before receiving another command; none of this improved the situation. I added indicators and arrays to
capture the last several strings that were input to the VISA function, but I saw nothing unusual. All I've been
able to determine is that the VISA abc W function hangs as described in my posted message.
Attachments:
VISA Write Hang 9-15-05.zip ‏282 KB

I need to sort an array of strings based on the number in each string.

Basically, I have a directory of files that all have the same name but each with a different number on the end.
example: image 1.jpg, image 2.jpg, etc.
When I use the List Directory function that returns an array of strings containing the file names in the directory, they don't come out in a 1, 2, 3, order like they appear in the directory. It sorts them character by character so that they come out like: 1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 2, 20, 21, 22 etc.
Is there a simple way of sorting this array of strings with the file names (as above) so that they are in numerical order?

It's a while since this thread was started, but I am sure others will have use for this so here goes:
The in-built array sort function sorts the strings the same way DOS and Windows do. Microsoft has fixed this in the Explorer that comes with XP, however the rest of the OS(s) still sorts the old way.
The attached "AlphaLogical String Array Sort" VIs will sort strings arrays the same way as the new XP Explorer. There are three different implementations of the sorting, one based on the Insertion sort algorithm, a Quick Sort based on recursive calls (the most elegant way, but unfortunately LabVIEW has too much overhead when doing recursive calls so this is actually a very slow alternative) and finally the fastest; a stack based Quick Sort. There is also a test VI that will show you how the different implementations perform.
I had not used recursive calls in LV much until I made the attached quick sort and was a bit disappointed by the fact that it is so slow, but it's a good learning example...The ability to do recursive calls this way was introduced in LV7 I believe...There is an example here on the zone that shows how you can calulate a factorial by using recursive calls, however - unlike for the quick sort (normally) - recursive calls are actually not the optimal solution for that calculation.
Message Edited by Mads on 09-13-2005 02:30 AM
MTO
Attachments:
AlphaLogical Sorting.zip ‏142 KB

"Using a CIN to Create an Array of Strings in LabVIEW" example crashes LV on Linux

Tried to utilize this NI example: "Using a CIN to Create an Array of Strings in LabVIEW" (http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B4B282BE7EF907C8E034080020E74861&p_node=&p_source=External)
Compiles OK with the makefile made by the LV's lvmkmf utility. Nevertheless when I try to run the VI (with the code loaded into the CIN, of course), LabVIEW 7.1.1 on a SUSE 9.3 Linux machine crashes:
LabVIEW caught fatal signal
7.1.1 - Received SIGSEGV
Reason: address not mapped to object
Attempt to reference address: 0x0
Segmentation fault
Any ideas? Did anybody try this on a Windows machine?

H View Labs wrote:
Tried to utilize this NI example: "Using a CIN to Create an Array of Strings in LabVIEW" (http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B4B282BE7EF907C8E034080020E74861&p_node=&p_source=External)
Compiles OK with the makefile made by the LV's lvmkmf utility. Nevertheless when I try to run the VI (with the code loaded into the CIN, of course), LabVIEW 7.1.1 on a SUSE 9.3 Linux machine crashes:
LabVIEW caught fatal signal
7.1.1 - Received SIGSEGV
Reason: address not mapped to object
Attempt to reference address: 0x0
Segmentation fault
Any ideas? Did anybody try this on a Windows machine?
This code is badly broken. In addition to resizing the actual handle to hold the number of string handles you also would need to create the string handles itself before attempting to write into them. NumericArrayResize is the fucntion to use as it will either resize an existing handle (if any) or create a new one if the value is uninitialized (NULL).
/* resize strarr to hold handles to NUMSTRINGS strings */
err = SetCINArraySize((UHandle)strarr, 0, NUMSTRINGS);
if (err)
goto out;
/* perform this loop once for each element */
/* of array of strings being created */
for (i = 0; i < NUMSTRINGS;) {
LStrHandle handle = (*strarr)->arg1[i];
/* determine length of string that will be element of strarr */
strsize = StrLen(str[i]);
err = NumericArrayResize(uB, 1, &handle, strsize);
if (err)
goto out;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/* moves strsize bytes from the address pointed to */
/* by str[i] to the address pointed to by the data pointer in the handle */
MoveBlock(str[i], LStrBuf(*handle), strsize);
/* manually set size of string pointed to by *strarr */
(*((*strarr)->arg1[i]))->cnt = strsize;
/* manually set dimSize of strarr */
(*strarr)->dimSize = ++i;
return noErr;
out:
return err;
Rolf KalbermatterMessage Edited by rolfk on 06-30-2005 03:15 AM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

How can I resize an array of strings?

I'm having a problem of not being able to use the CIN functions and therefore can't use the convenient resizing methods. I have tried to use NumericArrayResize to resize an array of strings, but it's not working correctly. Here's what I've tried most recently. I have tried many variations, so if you want to modify what I have posted, or just provide new code, please feel free.
typedef struct {
int32 dimSize;
LStrHandle elt[1];
} LStrHandleArray;
typedef LStrHandleArray **LStrHandleArrayHandle;
void someMethod(LStrHandleArrayHandle arrayOut) {
// attempting to write the string "asdf" in the first element in the array. (1D array)
int newSize = 1;
MgErr e = NumericArrayResize(uL, 1L, (UHandle*)&arr
ayOut, newSize);
(*arrayOut)->dimSize = newSize;
LStrHandle hdl = *(*arrayOut)->elt;
long str_size = strlen("asdf");
MgErr err = NumericArrayResize(uB, 1L,(UHandle *)&hdl, str_size);
LStrLen(*hdl) = str_size;
MoveBlock("asdf", LStrBuf(*hdl), str_size);
The code above doesn't result in crashing labview at any time. The string "asdf" is not copied though. And, after being able to copy one string I would like to extend this to many elements in a 1D array of strings.
Thanks!
Naveen

LabVIEW stores string arrays as an array of handles to those strings. To resize an array of strings you need to declare a new string in LabVIEW's data space, resize the handle array, and add a handle to your new string. Here is an example program which does this.
-Aaron Marks
National Instruments
Attachments:
resize.zip ‏252 KB

Visa Write go slow

I have a LabVIEW program which uses a duplicate session to write stuff to an Arduino and read stuff from an Arduino. After running for some time, occasionally some of the VIs "freeze". This was on an executable so I haven't investigated what's going on there.
I put an EZ Tap Pro snooper on the Tx and Rx in the Arduino and found that the characters were being written with a delay between characters. The Arduino reply is quick as normal.
I am struggling to see how the VISAWrite can decide to go slow. The Visa session is set to have no handshaking. To me the whole string should be written into the PC write buffer and the UART should spit the thing out the serial port with no delays. The PC is connected to the Arduino via USB but as far ask I know the PC thinks it's like a serial port.
Can there be anything in VISA Write which drip feeds characters to the UART?
This is early days in solving the problem. The software runs well for hours and hours without crashing
Thanks for any clues

pgaastra wrote:
I have a LabVIEW program which uses a duplicate session to write stuff to an Arduino and read stuff from an Arduino. After running for some time, occasionally some of the VIs "freeze". This was on an executable so I haven't investigated what's going on there.
I put an EZ Tap Pro snooper on the Tx and Rx in the Arduino and found that the characters were being written with a delay between characters. The Arduino reply is quick as normal.
I am struggling to see how the VISAWrite can decide to go slow. The Visa session is set to have no handshaking. To me the whole string should be written into the PC write buffer and the UART should spit the thing out the serial port with no delays. The PC is connected to the Arduino via USB but as far ask I know the PC thinks it's like a serial port.
Can there be anything in VISA Write which drip feeds characters to the UART?
This is early days in solving the problem. The software runs well for hours and hours without crashing
Thanks for any clues
clues?
how about posting your VI ?

VISA Read Timeout and VISA Write not working

I'm writing a program that sets a triangle wave pattern voltage (using Triangle Wave VI) to a DC power source (GWInstek PST-3202) through a RS-232 connection. I know my instrument parameters are set up correctly because I've been able to control this power source using a different VI with the same parameters. I also know I am connected to the power source because I can talk to it using MAX. I have a string indicator before my VISA Write statement that shows me the command being sent to VISA Write. It shows the correct syntax for setting a voltage on this instrument. However, when I run the VI, the voltage is not changed on my instrument, even though the correct command is sent to the instrument. After the VISA Write operation I have inserted a VISA Read function in order to read the newly set voltage from both a numeric and a waveform indicator. Using the Error Out cluster I am able to see that there is a timeout error from VISA Read. I thought perhaps I needed to clear or flush the buffer after each Read statement, but that didn't work either. I'm stumped as to why VISA Write isn't writing to the device. I have included my VI below, as well as the initialization subVI for the power supply.
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
Unofficial Forum Rules and Guidelines

Not using an array of strings

how do I write a java method without using an array of strings?
for example:
import java.io.File;
public class rename
public static void main(String[] args)
File src = new File(args[0]);
File dst = new File("c:\\temp\\temp.txt");
boolean wasRenamed = src.renameTo(dst);
I don't want to have main use an array of strings but I want rename to work as a class

This is what I changed it to and am getting an -- Exception in thread "main" java.lang.NoSuchMethodError: main
Sorry this is my first java program
import java.io.File;
class App {
     private App() {
          super();
     static final public void main(final String[] args) {
          switch (args.length) {
               case 1:
                    try {
                         Rename rename = new Rename();
                         rename.rename("c:\\felss\\charles.txt.bak"); // see, it's kind of silly to have same names for class and method
                         System.exit(0);
                    catch (Throwable e) {
                         e.printStackTrace();
                         System.exit(1);
                    break;
               default:
                    System.err.println("Usage: java App [new name]");
                    System.exit(1);
public class Rename {
     public Rename() {
          super();
     final public void rename(final String newName) {
          File src = new File(newName);
          File dst = new File("c:\\felss\\charles.txt");
          boolean done = src.renameTo(dst);
}

Array to String (VISA Write)

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