Multi-Case-Structure

Hello,
what is the best way to create an multi-case structure for checking many logic states in once? I need it for a simple state machine which is controlled by some digital sensors in the way:
WHEN DI0; DI2 = TRUE and DI1 and DI3 = FALSE then .........state1
WHEN DI0; DI3 = TRUE and DI2 and DI1 = FALSE then .........state2
WHEN all DI = TRUE then ........ error state
And so on... has someone an idea? Maybe I am a little bit slow?! ;-)
Thanks!
Paul

How are you reading the DIO? I would be tempted to just read the port (8 digital lines) as a U8 and then that value can go straight to the case selector.
The other option is to read the 3 lines as an array of booleans and then use Boolean Array To Number whose result can then go into the case selector.
If using numbers, you can set the radix of the case structure so that you can view the state case in boolean. Might make it a little easier to understand what is happening.
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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!
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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
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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
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Attachments:
implies.png ‏8 KB

How to get a case structure to execute only once in a loop

I have a while loop that is monitoring temperature. Once the temperature meets or exceeds a given setpoint I want to start a timer. At this point I don't want to monitor the temperature anymore. That is, if the temperature should drop below the setpoint, I don't want to execute the case structure again when the temperture meets or exceeds the setpoint(the temp may oscillate about the setpoint for a given period of time). In any event, I need the case structure to execute only one time, not every iteration of the loop.

You can put a local Boolean variable "Flag" inside that case structure and
set "Flag" to False. Outside the case structure, use an "AND" function
output to control the case structure. The "AND" function has two inputs. One
goes to the comparison results between real temp and setpoint. The other
inputs connects to the "Flag" variable. In this way, once you entered that
case structure, the "Flag" will be turned to False, and then in next
iteration, you won't get into the case again because the "AND" function will
be False as your "Flag" is False now.
Hope this helps.
Rentian
1. Inside the case structure, put a
"BB Herman" wrote in message
news:[email protected]..
>I have a while loop that is monitori
ng temperature. Once the
> temperature meets or exceeds a given setpoint I want to start a timer.
> At this point I don't want to monitor the temperature anymore. That
> is, if the temperature should drop below the setpoint, I don't want to
> execute the case structure again when the temperture meets or exceeds
> the setpoint(the temp may oscillate about the setpoint for a given
> period of time). In any event, I need the case structure to execute
> only one time, not every iteration of the loop.

Possible to do this with case structure?

Essentially I want the case structure to do: If case1 = run OR case2 = run, do this, else do case3++
I'm using a string case structure right now, where for example, the inputs could be SWEEP_A or SWEEP_B but I want the case structure to use case SWEEPAorB. This is so I can have different names for the input string BUT run the same case (this is to avoid redundant code for what I'm doing).
Thanks.

For more complex logic use can use create a boolean array and convert it to a number.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot

How can I put a numeric indicator into a case structure using VI scripting

I'm using VI scripting and I'm trying to add a numeric indicator inside a case structure. I'm able to add the case structure and the numeric indicator just fine, but as soon as I specify the case structure as the "owner" of the numeric (as opposed to the block diagram being the owner) I get error 1060. Is there any way around this?
Note: The reason I am doing this is because this specific pattern (indicator in a case structure) will prevent a VI from being inlined when it is being built. This pattern will provide no functionality in itself, it only prevents the inlining. It is added to a larger VI which is use to initialize objects in a simulation, and there are many of them in the total simulation. If they are inlined, it takes a VERY long time to generate the C code, and performance on this VI isn't an issue since it is performed only once at the beginning of the simulation. The rest of the VIs do need to be inlined for performance reasons. Therefore, I'm open to other options to prevent a VIs from being inlined if the "indicator in a case structure" cannot be performed via scripting.
If any of this is unclear please let me know and I can clarify. Thanks.
Solved!
Go to Solution.

I now understand what you were saying about inlining a subvi. I did as you said and made a subvi with a case structure and an indicator within it. I use the New VI Object node to add that subvi to the slow-inlining parent VI. Then I tried to inline it using the invoke node, but I got error 1399, which make sense. Is this what you meant for me to do, or did I misunderstand?
Also, I tried the ControlTerminal reference approach you mentioned earlier. Unfortunately when I called the move method on the control terminal property and had the 0th frame of the case structure as the owner I got error 1060 again.
I really appreciate your help. Do you have any other thoughts?

Keeping count of how many times a case structure has been entered.

I have a "Case" structure (when a button is pressed, it is "case True").
I want to keep track of how many times this "case True" has been entered.
How can I do this?
Solved!
Go to Solution.

For that you need to have a shift register or a feedback node and keep counting whenever the case structure case is executed the count will be increased by one see the attached snippet.
Good Luck
The best solution is the one you find it by yourself
Attachments:
CaseStructure count.png ‏10 KB

Resetting a Case structure

I am writing a VI that reads in a signal to a comparator and sends the
output
to a
case structure.
The ides behind the project is EMG (monitoring muscle active/inactive
times).
The case structure is as follows:
If 1: count up and if count reaches 10 then green LED on (represents muscle
active)
If 0: count up and if count reaches 10 then red LED on (represents muscle
inactive
and should be exercised.)
My question is how could I reset the case structure to start again: i.e, If
Case=0
and the inactive time reaches 10 and RED LED comes on, I want this to then
turn
off
and put the count back to 0 if it switches to Case=1.
(The idea is that this RED LED is representing a Vibrate motor (which I
will
output
to using DAQ) . The motor will switch on as the RED LED does to indicate to
a
user
muscle should be exercised but I do not want the motor to be on constant, I
need it
to turn off when the muscle is exercised and then restart the count again)
I probably haven't explained this very well but I have attached my VI.
Any help would be appreciated
Solved!
Go to Solution.

PinkLady4128 wrote:
The case structure is as follows:
If 1: count up and if count reaches 10 then green LED on (represents muscle
active)
If 0: count up and if count reaches 10 then red LED on (represents muscle
inactive and should be exercised.)
What is the count interval? How is the count increment triggered (time ie: every second?)
My question is how could I reset the case structure to start again: i.e, If
Case=0 and the inactive time reaches 10 and RED LED comes on, I want this to then
turn off and put the count back to 0 if it switches to Case=1.
Do you want the reset to occur automatically and restart? Do you want someone to notice the RED LED? If it resets, do you want to start again but keep the RED LED on which also indicates that the motor is running?
(The idea is that this RED LED is representing a Vibrate motor (which I
will output to using DAQ). The motor will switch on as the RED LED does to indicate to
a user muscle should be exercised but I do not want the motor to be on constant, I
need it to turn off when the muscle is exercised and then restart the count again)
So while it is counting, if there is muscle
movement detected, do you want the motor to stop and the RED LED to turn
off?
I probably haven't explained this very well but I have attached my VI.
You forgot to attach your VI

Problem with multiple sub-panels through Enum case structure: "The VI is not in a state compatible with this operation"

Hello,
I am using LabVIEW 8.0 and I am attempting to create a sub-panel that displays the front panel of a sub-vi depending on the selection made by the user via the Enum dropdown menu. I have wired the Enum to a case structure and applied identical coding to each individual case structure except for obviously changing the sub-vi source. However, I receive an error "The VI is not in a state compatible with this operation." I was able to successfully make a single sub-vi work within a sub-panel using a true/false case structure and the exact same coding. However, now that I am using an Enum box wired to a case structure, I receive this error. I have attached my block diagram as well. Could anyone assist me as to where it is that I am going wrong?
Thanks in advance!
Solved!
Go to Solution.
Attachments:
enum subpanels.JPG ‏22 KB

torm wrote:
I have attached my block diagram as well
I only see a picture. Can you attach the VI instead? At what point do you close the reference?
torm wrote:
I have wired the Enum to a case structure and applied identical coding to each individual case structure except for obviously changing the sub-vi source.
Well, if the code is identical except for the source, only the source should be inside the case, right? Why duplicate code?
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