I'm trying to pass data which is continuously changed from the inside of one While loop to the inside of another While loop of a sub-vi. The main program on the left is constantly reading new data and the program on the right is adding 1 to the new value. My issue is that I cannot input new values to a While loop which is already running and thus my sub-vi is never updated. I've tried a global variable ("write" from the main program control and then "read" into the sub-vi) but that doesn't work either (same result as if the main were just passing data into the sub).
I apparently don't have enough reputation to post a picture of my program but I'm basically trying to run parallel loops (almost inside each other). Can anyone lend me an experienced hand?
The most common problem with while loops are based on lack of knowledge how exactly does the while loop work in LabVIEW.
First of all the information will be given outside the loop only if the condition terminal (right down corner of the loop) will be flagged as true.
If you want to pass the data earlier (while the loop is running) you have to choose easiest option:
Use queue (is the most common and well working). I can elaborate how this one work in practise if you want, or just try to run an example from LabVIEW help.
local/shared variables - you can define in your own library variables and pass the data by READ/WRITE option.
Please try to upload some documentation to an external server (as you are blocked here), and post a link, and then I could help you with a specific example.
Help»Find Examples. Search for "queue". Pick out an example with parallel loops.
You might want to look into Queues or Notifiers as means of passing data between running loops.
Related
So i have a problem which I modeled using PDDL. I want to implement the plan generated from this problem to a an existing Python code which controls two motors via Wi-Fi with a loop on VS Code (Python). I want this code to take my plan and execute it. Does this mean I need to define the actions I have as functions for my Python code and read the .plan file as a text and call the functions step by step? What are other options I might have?
Thank you for sparing your time!
Yes, it means that for every action of your PDDL, you have a corresponding function. And for every object in your problem, you have a corresponding instance that you can pass as an argument to the functions.
When you get a plan, you must parse it, take the step of the plan and:
look up the function by your action name
look up the instances by name to pass them to the function.
Once the function completes successfully, repeat.
Note that if you want to be able to interrupt the action while it is ongoing, you might need more complex kind of functions, if not objects.
I was wondering if there were a way to compute the size of a reg in Verilog. I researched it quite a bit, and found $size(a), but it's only in SystemVerilog, and it won't work in my verilog program.
Does anyone know an alternative for this??
I also wanted to ask as a side note; I'm having some trouble with my test bench in the sense that when I update a value in the file, that change is not taken in consideration when I simulate. I've been told I might have been using an old test bench but the one I am continuously simulating is the only one available in this project.
EDIT:
To give you an idea of what's the problem: in my code there is a "start" signal and when it is set to 1, the operation starts. Otherwise, it stays idle. I began writing the test bench with start=0, tested it and simulated it, then edited the test bench by setting start to 1. But when I simulate it, the start signal remains 0 in the waveform. I tried to check whether I was using another test bench, but it is the only test bench I am using in this project.
Given that I was on a deadline, I worked on the code so that it would adapt to the "frozen" test bench. I am getting now all the results I want, but I wanted to test some other features of my code, so I created a new project and copy pasted the code in new files (including the same test bench). But when I ran a simulation, the waveform displayed wrong results (even though I was using the exact same code in all modules and test bench). Any idea why?
Any help would be appreciated :)
There is a standardised way to do this, but it requires you to use the VPI, which I don't think you get on Modelsim's student edition. In short, you have to write C code, and dynamically link it to the simulator. In the C code, you can get object properties using routines such as vpi_get. Useful properites might be vpiSize, which is what you want, vpiLeftRange, vpiRightRange, and so on.
Having said all that, Verilog is essentially a static language, and objects have to be declared with a static width using constant expressions. Having a run-time method to determine an object's size is therefore of pretty limited value (since you should already know it), and may not solve whatever problem you actually have. Your question would make more sense for VHDL (and SystemVerilog?), which are much more dynamic.
Note on Icarus: the developers have pushed lots of SystemVerilog stuff back into the main language. If you take advantge of this you may find that your code is not portable.
Second part of your question: you need to be specific on what your problem actually is.
Labview is very frusturating to me having used C/Java before.
I have a simple problem I dont know how to solve.
My program does some operations in a loop and updates an indicator inside the loop. I would like to make this loop (and the inputs it requires) into a VI but I have no idea how to make the indicator an output of the VI.
I would like to be able to reuse this VI, connect an indicator to it, and have it automatically update without creating any loops outside of the VI.
In C I would be able to do this by either returning a pointer or passing by reference to a function.
Use a queue to move data between loops in block diagrams.
The producer/consumer pattern uses a queue to move the data between two loops on the same diagram, but a queue is global to a VI hierarchy and by naming it when you create it, a second VI can obtain a reference to it by using the same name.
NB: queues are 1:1 and lossless; if you need 1:N data transmission, use a notifier (which is newest-value lossy) instead.
In LabVIEW while loops have simple condition. The value can go outside the loop only when we will meet the condition. There is a condition terminal in the right down corner of the loop.
At general:
1) When true flag will be set there (stop if true) then the value will be passed outside the loop.
2) When the false flag will be set there (continue if true), then the value will be passed outside the loop.
3) You can always use error wires with condition terminal inside the loop, when error will be raised, then loop will stop.
In your case:
Always try to use the smallest amount of while loops as it is possible due to optimalization reason.
1) You can use while loop in your main VI, while all SubVIs will be in this loop and all values (indicators) will be updated.
2) You can try using while loops inside subVIs, but then you have to provide mechanisms that will transport values outside the loop such as queues or local variables
You can make a reference for a labview indicator as well, but you would need to make it a global variable or pass in the reference from the calling vi.
As for your frustrations, you should know that you can pretty much do anything in Labview that you can do in C.
A) The image below shows how to do this.
B) This style of programming works in small applications, but as an application grows larger, I would encourage you to explore an actual architecture for producing data in one hierarchy and consuming it in another (as alluded to by other answers to this question). In particular, do File >> Create Project and choose the Producer/Consumer template to explore a good starting point for such architectures. There are more sophisticated ones, but that makes an excellent beginning.
I am making my existing .Net Application Scriptable for non programming users. I added lua, it works like a charm. Then I added debug functionality(pause/continue/step) via debug.sethook. It works also like a charm.
Now I realize that my Application needs edit and continue feature like Visual Studio has it. You pause the execution can edit the code and then continue from your current state with changes applied. This feature is very important to me. I thought this would be easy to do for scripting languages.
Everywhere I read that scripting languages can do this. But even after spending hours of searching I haven't found an Lua implementation yet. It hasn't to be Lua but hot swapping code in Lua would be my first choice.
How can the ability for the user be offered to pause and edit the script and than continue the execution with changes applied?
NOTE: It doesn't have to be Lua every scripting language would be okay
Update
#Schollii
Here is an example:
function doOnX()
if getValue() == "200" then
value = getCalculation()
doSomething() -- many function calls, each can take about 2s
doSomething()
doSomething()
print(value)
doX(value)
end
end
doOnX()
Thank you for your suggestions. This is how it might work:
I will use https://github.com/frabert/NetLua Its a very cool, well written 100% C# Lua Interpreter. It is generating an AST tree first and then directly executing it.
The parser needs to be modified. In Parser.cs public Ast.Block ParseString(string Chunk) there is a parseTree generated first. parseTree.tokens[i].locations are containing the exact position of each token. The Irony.Parsing.ParseTree is then parsed again and is converted to a NetLua.Ast.Block but the location information is missed. I will need to change that so later I will know which Statement is in which line.
Now each Statement from the AST tree is directly executed via EvalBlock. Debug functionality (like I have in my C Binding lua Interpreter DynamicLua via debug.setHook) needs to be added. This can be done in LuaInterpreter.cs internal static LuaArguments EvalBlock(`. Pause/continue/step functions should be no problem. I also can now add current line Highlighting because each statement contains position line information.
When the execution is paused and the code was edited the current LuaContxct is saved. It contains all variables. Also the last Statement with the last execution line is saved.
Now the code String is parsed again to a new AST tree. It gets executed. But all statements are skipped until the saved statement with the line statement is reached. The saved LuaContext is restored and execution can continue with all changes applied.
New variables could be also added after the last executed line, because a new NetLua.Ast.Assignment Statement could just add a new variable to the current LuaContext and everything should just work fine.
Will this work?
I think this is quite challenging and triicky to do right.
Probably the only way you could do that is if you recompile the chunk of code completely. In a function this would mean the whole function regardless of where edit is in function. Then call the function again. Clearly the function must be re-entrant else its side effects (like having incremented a global or upvalue) would have to be undone which isn't possible. If it is not reentrant it will still work just not give expected results (for example if the function increments a global variable by 1 calling it again will result in the global variable having been increased by 2 once the function finally returns).
But finding the lines in the script where the chunknstarts and ends would be tricky if truly generic solution. For specific solution you would have to post specific examples of scripts you want to run and examples of lines you would want to edit. If the whole user script gets recompiled and rerun then this is not a problem, but the side effects is still an issue, examples could help there too.
I have a large, somewhat messy For loop in which I can not find the iteration number box. Is there any way of searching for this component or simply creating a second iteration number box?
You can't create a second iterator terminal, but you can use scripting to move the iterator to a typical location (bottom left) with this VI Snippet.
Be sure the file is open before running the script.
This is a bit of a gamble, but you can try the Clean Up Diagram tool and see if that helps. If it doesn't it should still expose the iteration icon, and you can find out what wires it is connected to. Hit Ctrl-Z to undo the clean-up, and double click on the wire indicated previously and it should expose everywhere the wire routes to. Hopefully you can track it down then.
A messy diagram means that sub-vis or an architecture re-design is badly needed.
Depending on what version of labview you are using, you can use Block Diagram Cleanup tool, as mentioned by Austin. But you can also highlight a section of code and clean that up individually. This 'selective cleanup' feature was introduced in 2012.
Regardless, you can't search for an iteration counter. Use your eyeballs...how bad could this for loop be? Hint hint: I want to see it :-)