Error in continuously saving waveform data

[rajesh111]

In the attached VI, I am trying to display the numbers coming out of a random generator with respect to time, write this data to a binary file and then reading the waveform by calling that particular file. I want to display the write and read data waveform simultaneously. The VI is running fine except that it is showing a dialog box again and again to 'Replace the existing file'. Can somebody tell me how can I get rid of that popup message?

[GerdW]

Hi meetrajesh,

The VI is running fine except that it is showing a dialog box again and again to 'Replace the existing file'. Can somebody tell me how can I get rid of that popup message?

This message is created in a subVI of WriteWaveformToFile - you can dig into the function and its subVIs…

To get rid of that message you should NOT edit those subVIs - they are part of the LabVIEW installation.

Instead you need to delete the file before trying to overwrite it!

(Your VI is some weird kind of Rube-Goldberg! Why do you need to write a waveform to a file, just to load the file again? And then export the waveform data to a different file again…)

[rajesh111]

Actually my aim is to import this design to a PID controller application. The program will keep on writing/storing the current values of P, I and D to a text(and binary) file with respect to time and we can read/plot the data points on a waveform graph as and when required. Like 3 select buttons (one each for P, I & D) can be provided to display the 24 hour data. For the time being, I have made 2 separate VIs, one for writing the data and other to read the data. 'Write waveform to file.vi' & 'Read waveform from file.vi' accepts binary file format so I used '.txt' as well as '.dat' format. The problem I am facing is in the graphwrite.vi. Whenever I run this VI, it continuously asks to replace the existing file, as shown in the attached pic. How can I get rid of this issue? I think delete option will not suffice, as it would create some problem in graphread.vi. 

[crossrulz]

You really should not be continuously reading the waveform file.  Instead, use a queue to send the data to your "read" loop.

[rajesh111]

I have recently started working on LabVIEW and I don't know which function should I use to send the data through a queue. And secondly I am facing the issue in writing the values (and not in reading). In graphwrite.vi, it is again and again showing that dialog box to replace the file. How to write the data values continuously without any popup message?

[RavensFan]

Make sure you feed it a file path!

[rajesh111]

You are not getting my point. I am feeding the same .dat file path in writing and reading. When I run both graphread and graphwrite simultaneously, the write program keep on asking me to replace the existing file. I want to get rid of that popup and store the data to the specific file continuously.

[GerdW]

Hi meet,

did you read message#2?

You may also append to existing file instead of overwriting it again and again! ( Read the help for the WriteWaveform function...)

[crossrulz]

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@rajesh111 wrote:

I have recently started working on LabVIEW and I don't know which function should I use to send the data through a queue.

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Then I recommend you check out the Producer/Consumer.