Problem with one control in Subvi to use in MainVi...

Question

Hi,
I'll try to explain easy. I have my application with main window, where I do calculates and have one graph data. I use subvi to open the serial port and when I close the subvi, the data is drawed in the mainvi graph. Now I am trying to implement one option to do several test from serial port automatically. I want to have one Control Bottom in subvi, that when I active it, When I close the Subvi acquisition data, automatically active the save bottom and save the file and THEN open again the subvi ready to acquire another run of data. So I only need to start/Finish the data entry and it will going save diferent test in file.
I tried several things, but I have the problem when I active the option. In the first time, appear me BEFORE the execution of Subvi than the option to save the file. In the second run it seems works well, so 3rd,... the problem come when I disable the option in the Subvi and when I close the window in the mainVi the values aren't changed and appear the new save option and Subvi several times, until the iteration change and put 0 value and it works normally again. I am trying to retard the for/else 1 or 2 iterations but I dont know to do it, since The iteration value is increasing from starting the program and when I open the Subvi it only stops to count and when I come back again to Main continues with the last value. I would need the iteration of loop reset to 0 to say to the for/else to wait 2 iterations or use any counter... I tried to do it, but I spent my ideas.
I tried to do one example program in Lv7.1. 
It have the same structure and the same problem that in my program. In this example even I can't close the subvi between it is saving and re-openning it. I suppose since It is so simple, the active value do the subvi open directly.
I hope you tell me any idea to do it.
Regards, Fonsi.
Attachments:
Main.vi ‏55 KB
Subvi2.vi ‏14 KB

Answer 1

The reason why you seem to need that "extra run" is due to a race condition. If you watch your code in highlight mode you will see this. You have 3 independent case structure. Let's say you start the VI and then press the "Start Test" button. The main VI is now executing the True part of the top-left case. Meanwhile, the other two case structures are executing since there is no data dependency. They see the values of the local variables as they were when you pressed that "Start Test" button. You set the "Active Multiple Runs" to True. The top-left case ends, and now the loop can go to the next iteration since all code has completed. In this iteration "ActMultiple" is True, so in the bottom case structure you execute the True case where you delay for 0.5 seconds, and then set "NewRun" and "MultSave" to 1. Meanwhile, the other two cases have already run. You now finish this iteration and move to the next. In this iteration the top-left case evaluates to True since "NewRun" is 1. So you get the dialog. While the dialog is up, the other two cases have already finished. You set the "Active Multiple Runs" control to False. The subVI ends, "ActMultiple" is set to False. and the loop iteration completes. Next iteration. Even though "ActMultiple" is False, you are probably thinking that you will get the "NewRun" and "MultSave" set to False because of the bottom case structure, so the top-left and top-right should see the values. This is not what happens. LabVIEW will read the values of the local variables before you enter the bottom case structure to set them. This is the race condition.