CASE structure limits - dynamic?

Hello everybody
Is this possible, and if, then how, to make the CASE structure
condition dependent on variable in my program.
Egsample: I have integer and the value of this is changing during
program running, and I need from some reasons, to make the CASE
structure sensitive for the values of this integer. How I can do
this?
I know there is always way around, but I am interested in this
solution.
thanks in advance
regards
PP

Hi Pawel,
I am starting a new thread because I think I know what you are asking for.
First of all, you can not change the values of the case structure itself BUT,
there is a way.
What I suggest is the following;
1) Code your second case as normal. Pretend it has 3 cases 0,1 &2.
2) Code the first case (just example) such that is has two cases A&B.
3)Have the first case state A return an array of (3)strings that is "Good", "Bad", and "Ugly".
4)Have the first case state B return an array of (3) strings that is "Bad", "Ugly", and "Good".
Feed the above mentioned arrays into a serach 1-d array function. Use the retuned index to select the proper case of "the second case".
If you now pass "A" to the first case structure, and "Good" to the "se
arch 1-d array" it will return an index of 0 and the second case will execute case "0".
If you pass the first case "B" and again pass "Good" to the "serach...." it will return an index of 2 and the second case will execute state "2".
So,
by manipulating the arrays returned by the first case structure, you can "dynamically" influence which of the states of the second case is called.
There are many variations on this idea that are possible. A similar approach would make it possible to select states based on wildcards and simulate "sparse enums".
Did I nail it this time?
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

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Case structure and dynamic data, maybe once again

Hi there,
I`m a beginner in Labview. I´d like to know, how to handle the attached case-structure so that the structure works with each point of the signal.
Right know the signal is only analyzed one time.
Thanks for your help
Michael
Attachments:
prob.jpg ‏26 KB

Thank you Lars!!
Now it works
Solution is given as attachment
Attachments:
lsg.jpg ‏46 KB

To create a deep structure for dynamic internal table.

Hello
My ALV has fields which are defined dynamically during execution.
so, i did it in the following way,
Declared Field symbolds, DREF and fieldcatalog as,
FIELD-SYMBOLS: <t_dyntable> TYPE STANDARD TABLE,
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DATA:   dref_dyntab    TYPE REF TO data,
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DATA: ts_fieldcatalog TYPE lvc_t_fcat.
DATA: wa_fieldcatalog TYPE lvc_s_fcat.
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*function module to read segment structure
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*--Method to get the structure of table using fieldcatalog.
CALL METHOD cl_alv_table_create=>create_dynamic_table
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*--Variable of type REF TO DATA.
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IF sy-subrc <> 0.
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*--Dynamic internal tables required when show segments selected
IF p_selseg IS NOT INITIAL.
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CL_GUI_ALV_GRID => SET_TABLE_FOR_FIRST_DISPLAY
for ALV grid Display along with above used filedcatalog ts_fieldcatalog.
Things are fine till here, but now i have the requirement to edit selected rows of the ALV display..
As you might be aware, we need a field
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in the output internal table <t_dyntable> to meet our requirement.
My issue is about declaring one such field of type 'h' in this dynamically created internal table ''<t_dyntable>".
I tried in the following way by adding one such field to fieldcatalog :
*Field for Styling
ADD 1 TO v_counter.
wa_fieldcatalog-fieldname   = 'TS_STYLEROW'.
wa_fieldcatalog-tabname     = 'TS_STYLE'.
wa_fieldcatalog-col_pos     = v_counter.
wa_fieldcatalog-no_out      = 'X'.
wa_fieldcatalog-inttype     = 'h'.      " I even mentioned this
APPEND wa_fieldcatalog TO ts_fieldcatalog.
CLEAR wa_fieldcatalog.
But this is creating a field of type 'C' in the table <t_dyntable> instead of what i was expecting
Guyz and respected,
Please advice me with the solution or ur ideas....
Note : The overall requirement is create a deep structure for dynamically generated internal table.
Your help is highly appreciated and unforgettable..!!!!!!!

hi,
Dynamic append
Dynamic internal table
Dynamic internal table
dynamic columns in ALV
Variant for dynamic selection
thanks

Range setting in case structure

Hello everyone! I'm working on an engineering project where I read in a sound input and if it's on high volume, a red led connected to a MyDaq box lights up, if it's on low, the green LED lights up, and both will be off if there's no sound input. I posted a screenshot of how my vi currently looks. The problem I'm having is, I want to set the range that will be considered as the low volume, and a range considered as the high volume on my case structures. I'm not sure exactly how to do that. I currently have an "In range" function there where I set the max and min values. THe problem with this is, it outputs a dynamic data that I cannot connect to the appended array. Any help would be great. Thanks!
Attachments:
projecttest2.vi ‏91 KB

Thanks for your response. I'm new to labview (which isn't really an excuse) and we just went through the real basic stuff for this course. That's why my code just looks like a mess. I'm just trying to use the case selector because I thought it'd be more efficient, since, if I think of it in written code, they're kind of like if-else statements, right? I thought I needed to multiply by a thousand because I am measuring the amplitude of sound input. Whenever I test it out, the numbers are really small. I just figured it'd be easier to multiply it by a thousand and set the range with bigger numbers. I'm also trying to get an LED to light up on a range of volume. That's why I need two comparisons. Like, if the volume is between the range of 2000 to 3000, the green LED lights up, and if it's between 1000 to 2000, then the red LED lights up. If the signal is equal to zero, then no light turns on. Anyway, I scrapped the whole idea of using case selectors because I don't have time to learn my way through it and finish on time. I attached a new version of my VI. It's a more simplified version. I don't know how to connect the LED boolean indicators into my array and into the DAQ Assistant (it's not on the vi yet but I do need one so the program knows to read the output into the LED's on my myDaq box. Sorry for the trouble! Thanks for any advice you can give.
Attachments:
projecttest1.vi ‏55 KB

Boolean in empty case structure

Hello Everybody,
I am a bit stuck with one of my case structures. I am trying to set "True" for Boolean constant in order to enable "write to file" of the data once the number in one of the dynamic data flows reaches threshold value 79. I want to make sure that all numbers will be written after that, and not only numbers >=79.
My idea was to put Boolean "True" in the true part of the case structure, and leave nothing in the false part of the case structure. That unfortunately did not work
Does anybody know if there is a way to set Boolean to "True" after I reach desired number and keep it at "True" afterwards for continuous recording?
I would really appreciate any help
Oleks
Solved!
Go to Solution.
Attachments:
loadcell_final_trig_qsw_3_08_2009.vi ‏416 KB

Just use a gobally initialized feedback node, less code.
Message Edited by altenbach on 08-03-2009 07:44 PM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
Loadcell.png ‏1 KB
LoadCell.vi ‏15 KB

Reading a field symbol whose structure is dynamic

Hi Experts,
I have used the concept of dynamic internal tables to select data from COSS/COSP for e.g.database tables.Field symbol of type " ANY TABLE" has been used to select data , as the dynamic structure is assigned directly to the field symbol.
To calculate the values of various fields I need to read the this field symbol for diferent line items , but I get a compilation error saying " Key not Found ". I understand that I am not able to read the field symbol because its structure is of type 'ANY TABLE' .How do I read this field symbol ?
The field symbol gets the structure of dynamic internal table as formed initially by using class concept.Is their any way in which I could get the structure of this field symbol or any other way to read it?
Thanks in advance.
Regards
Reetwika

Hi Ritwika,
Even if u use the concept if dynamic internal table, u can read the each of the field of ur structure,
if u know the name of the field.
for example:
MATNR being one of the field of internal table
field-symbols : <fs> type any.
loop at <fs_it> into <fs_wa>.
ASSIGN COMPONENT 'MATNR' OF STRUCTURE <fs_wa> to <fs_matnr>.
" in this case matnr field value will be assigned to the field symbol <fs_matnr>, so it can be used further.
endloop.
" do reply if still confused.
Rohit G
Edited by: Rohit Gaharwar on Aug 12, 2009 11:51 AM

Case Structures in LabVIEW 8.5

Is there any way to have a case structure based on different file paths? In the VI I'm creating, there are limited number of files that a user can read in and I want to have different cases depending on which file path they chose.
Hopefully this question is worded well enough for you to understand what I am asking for.
Thanks!

I am assuming that with "different file paths", you mean different files in the same location. Is this correct?
Let's assume that all the files are in the same location.
In this case you could also just strip the path and wire the filename to the case structure.
It is somewhat better self-documenting.
Message Edited by altenbach on 06-12-2008 12:56 PM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
fileCase.PNG ‏6 KB

Can I put a READ function in a TRUE/FALSE case structure?

Hi,
I have a vi that operates as controller for a mechanical system of motors. There are several sensors of various types, that provide input to the vi, including encoders, whose period is being measured. The attached vi is the encoder period measuring part. It measures 15 periods and tells me the average of the 15 with each loop iteration.
In my application, the encoder period measurement is not needed unless the vi knows that ALL THE OTHER sensors in the hardware configuration are measuring values within the desired range. For example, Sensors A, B and C should all measure between 5-10. If they are all showing values between 5-10, then, we want the encoder value to read and display. If only one of the sensors, say A, is measuring 12, then, we don't want the period value to READ or be subsequently processed. So, it is easy to set up the sensors A, B, C, to give a TRUE or FALSE based on whether they are within range or not, and if all 3 are TRUE, then, that value can easily be passed to the case structure that holds my READ function for the period. Is this a good way to do this? The goal is to eliminate unnecessary execution time that the period READ function would consume, as well as all subsequent calculations that are performed on the period value collected. The period data is of no use if any one of the other sensors is not in the correct range.
If any one of the other sensors is out of range, we want to skip the encoder READ step altogether. So, it is easy to structure a BOOLEAN in my vi as shown in the attachment. If I do it this way, will it throw an error, or just skip the READ until the BOOLEAN is true again? Is there a better way to prevent the READ from happening if one of my other sensor values is not within the correct range?
Thanks,
Dave
Solved!
Go to Solution.
Attachments:
forum JUly 18.vi ‏26 KB

Sure, you can put a Read inside a case structure. For your application, just check that your sensors are all within range (Comparisons palette), then AND the T/F's and use the result of that for your case structure. (If you are already doing the in-range check, I can't see it here because you have 5 subVIs that I cannot open here.
Cameron
To err is human, but to really foul it up requires a computer.
The optimist believes we are in the best of all possible worlds - the pessimist fears this is true.
Profanity is the one language all programmers know best.
An expert is someone who has made all the possible mistakes.
To learn something about LabVIEW at no extra cost, work the online LabVIEW tutorial(s):
LabVIEW Unit 1 - Getting Started
Learn to Use LabVIEW with MyDAQ

How do I use a Case Structure with Strings?

I need to use a string list to set up a set of cases to be performed. Is it possible to tell a single case structure to do "a, b, c, and d, but not e or f" or "do a, c, d, and f, but not b or e" etc... when you use a string containing the cases to be used?

Blackavar,
A case structure will only execute a single case at a time. If you want to have multiple cases execute in parallel, then you would need to have multiple copies of the case structure and split the string apart and wire them to all of the needed case structures.
This could be done with reentrant subVIs to run truely in parallel. Anther method would be to have 6 different case structures, all with 7 cases each. The 7 cases would be "a", "b", "c", "d", "e", "f", and "0". Your input sting will need to be built up so that it will always be 6 characters long and then split up so that each character goes to one of the case structures. You would have your needed code for cases a - f. Case "0" would do nothing.
Randy Hos
kin
Applications Engineer
Nationsl Instruments
http://www.ni.com/ask

Can I use a formula node to start the execution of a case structure?

Hi,
I am working on editing a VI to make it much easier to understand (for colleagues and non LV users). For one reason or another, the VI's creators did not fully make use of the power of case structures and other structure types. In the application we need it for, the instrument cycles and repeats measurements on several objects. We are interested in measuring the motor currents for several motors in the system. As it stands now, for each sample object's run, there is a separate sub-vi diagram which displays its waveform trace and several indicators such as max current, time at max, etc. That code was contained within a T/F case structure and copied and pasted 20 plus times.... Obviously the vi became extrememly cluttered and needed a huge screen to see. The trigger for the current case structures is an EQUALS comparison between one input (which is the sample object counter; and this part I will likely leave unchanged since it makes a lot of sense already) and a constant which was defined 1 through 20+ for case.
I have since made one case structure and 20+ instances of that case and have labeled them (at the top selection box near the detent arrows) "1", "2", 3, etc. I am wondering if I can use a formula node to act as the "trigger" which sets each case structure running? I believe that a simple IF statement should work. Please see a snippet of my attempt at making this in C below.
For the node, I defined X as the input and Y as the output. The input to the node, X, is connected to the sample object counter. The output, Y, is connected to the case selector of the case structure. My attempt at the code is below:
int32 y
For(x == 1)
y = "1";
For(x == 2)
y = "2";
etc, etc.
Is that above code snippet correct? Do i need something like "ENDIF" or "end if" at the end? Does "y" have to be defined as "int32" or can it be something else?
Thanks for the help!

Is your formula node doing anything else besides what is shown?
Why don't you just wire the value that is going into it at X directly into the selector of the case structure?
Attachments:
Example_VI_BD.png ‏2 KB

How can I pass data generated in a SubVI inside a Case Structure out of the Case Structure?

Hello,
I am using a USB 2701 to control a heater. I have three SubVIs that are all working properly on their own. I'd like to use an Enum to select which of the SubVIs is running at a given time. The problem is that no data is passing out of the case structure. How can I pass the temperatures and heater outputs acquired by the SubVIs to the main VI? I've attached my some of my code below. I can't attach more than 3 files, but you can see how the main VI is configured. Like I said, the SubVIs are working individually, so you shouldn't really need to look at them.
Thank you,
CJones581
Attachments:
RampHeater6-21-07.vi ‏305 KB
69_Heater_Case.vi ‏23 KB
HeaterTCD6-21-07.vi ‏210 KB

CJones,
You might check a couple of things.
Your HeaterTCD... VI has a While loop with a stop button condition. HeaterTCD pass out values only when it finishes running. If it doesn't pop open the front panel (which usually doesn't happen when running a SubVI) you could run into a stuck loop because you don't have access to the Stop button. This could appear in the form of no data being passed out (because the SubVI never stops running). The primary VI opens the HeaterTCD VI, starts it, and waits for the VI to finish and pass final values .
Secondary note: Unless you want your SubVI panel (which probably isn't open when running the main VI) to update continuously, consider moving your Temperature Graph and Temperature oC indicators outside the while loop. Pass final values to them via a tunnel, since the main VI will only read their values after the loop finishes running, anyway.
It might help to add error management to HeaterTCD like you have for RampHeater. If you connect error lines with Error Outs to your main VI, that will help tell if there is an error somewhere that is preventing info output.
RampHeater SubVI has the same issue with the stop button. It is also probably getting stuck in the While loop waiting for a manual push of that SubVI's Stop button.
An easy way to test this would be to set up a logic circuit so that when the While loop iteration counter reaches a certain number, it registers True and sends it to the conditional. I know this isn't what you want to do long-term, but if that lets your SubVI return outputs it means that the SubVI was just never stopping.
Hope that helps.
David C, Applications Engineering
David C
Applications Engineering

How can I have multiple inputs into the selector terminal of a case structure

Hi everyone
I have a question on how to wire multiple inputs in to the selector terminal of a case structure.
Currently, I have three switches, each switch determines different case. So if I switch the switch 1 is on, the numeric indicator will show 1. If the switch 2 is on, the numeric indicator will show 2, so on and so forth. However, the selector terminal will not allow me to wire multiply inputs into the case structure, I tried Bundle by Name, Bundle and Array to Cluster, but they did not work. I set the case structure with 3 cases, they are 1, 2 and 3.
Could someone help me please. I have attach an image and the VI of the work I did so far.
I have another question, is there a function which can toggle other switches to off when there is a switch has been toggled on.
Thank you very much
Tommy
Attachments:
Trial - Case Structure.vi ‏7 KB

Tommy, attached find a cheeseball way of doing this that has given me a LOT of mileage over the years. IT lends itself nicely to a couple of really good practices that NI recommend, but I have given you the bare-bones to "see under the hood".
The recommended practices:
1. You can make this a nice tight sub-vi where you can put it into a core library of routines that you'll use over the years, even extending the logic to look only for changes, etc.
2. If you are thinking about Front Panel design considerations, you'll want to use arrays of controls where possible, as that's a nice neat way of containerizing your switch for both the FP and Block Diagram.
Have fun. I have TONS of these types of things, so feel free to PM me if you have any other needs.
Wes
Wes Ramm, Cyth UK
CLD, CPLI
Attachments:
Boolean Switch Logic.vi ‏11 KB

How do i output multiple arrays from a case structure to create one larger array

I currently have a vi that has one hardware input that i needed to take a measurement then be moved and take a similar measurement at a different point. To accomplish this i used a while loop inside a case structure. The while loop takes the measurement and finds the numbers i need while the case structure is changed per the new measurement location. I want to take the data points i have created in each case and output them into a single table. I assumed to do this the best way would be to get the data from each case into its own built array and build a larger array but I cant get the information out of the case structure so that it all inputs at different places.
thanks for your help
Attachments:
Array.vi ‏30 KB

Hi Ross,
attached you will find a solution for your table building problem.
I would suggest thinking about program design - having the same case content in several cases doesn't make sense. I also would not want my user to press several stop buttons depending on choosen measurement...
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome
Attachments:
Array.vi ‏45 KB

How can i use a string as a control for case structure?

my vi is reading data. the output is a string,how can a string can control the case structure? because the there's a constructed vi in that case structure that wll perform a tast after the main vi read.
Thank You
(Can you please give me a simple example how can do this)

Try this vi. You shouldn't have any problems just connecting a string to the case selector.
BJD1613
Lead Test Tools Development Engineer
Philips Respironics
Certified LV Architect / Instructor
Attachments:
string_to_control_case_structure.vi ‏10 KB

Run only once in case structure

Hello,
I have a menu set up that is wired to a case structure. Of course the menu is some boolean buttons that are set to switch when pressed so the case will stay open as long as the button is true.
inside that case I have another menu and a case structure that operates the same. In one of these cases I have a piece of code that I only want to run once. I have tried the while loop that runs once and a for loop that only runs once, but the section of code seems to run continuosly instead of just once. It works ok if I use any of the latch functions but not the switch when pressed functions. However, I need the button to stay pressed until the user is finished with that case.
I really don't want to use an event structure as I was saving that for another piece of code that monitors inputs.
Anyone have a suggestion?

Typically, this works easiest with a shift register and and a boolean "implies" function.
In the code example (see image), the button is set to "switch until released". (Of course you probably don't need the NOT, simply place your one-time code into the FALSE case )
Message Edited by altenbach on 01-26-2007 01:52 PM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
implies.png ‏8 KB

CASE structure limits - dynamic?

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