Wire Description to Write LVM File

[hema]

I have to give a title to my LVM file. The title is a string .
I am trying to wire the title string to the description input of WriteLVM file express vi. After i write, when i read back using Read LVM FILe Express vi, the description output is blank.
How to give a title string to LVM file and this should be done once. Its OK if the String does not appear in the LVM file when i open in Notepad.

[Bob_Y.]

There is no input for the description in the Write LVM Express VI. There is an input for a comment. If you wire something into the comment, when you read the file,it will be on the comment terminal, not the description terminal. The description terminal will have the description that you set on the Write LVM Express VI's configuration dialog.

I think you are looking in the wrong place for the wired string. I think you are setting the comment, so you should look at the comment.

I hope that this helps!

[Jeremy_L]

Hi,

If you double click to open the configuration of the Write LVM File VI, you should see a text box at the very bottom of this dialog. This is the description box. Unfortunately, there is no terminal input for this box. The only terminal input available for header info is the Comment box, which is probably what you're looking at. Try writing a string into the comment terminal, and open up the configuration dialog and write something in the description. Now read that file back, and set up a couple of indicators for the comment and description. You should be able to see the difference. Hope this helps!

Jeremy L.
National Instruments

[hema]

hello,
there is no description input for write LVM express vi. But i tried to make a description input in the VI by opening The LVM front panel and making a description input. Later i wired my string to this input, it did not work.if i wire comment, this input string appears in the file, i do not want the string to appear in .lvm file. so wiring description is ideal to me but it does not work.

[hema]

"hello,
there is no description input for write LVM express vi. But i tried to make a description input in the VI by opening The LVM front panel and making a description input. Later i wired my string to this input, it did not work.if i wire comment, this input string appears in the file, i do not want the string to appear in .lvm file. so wiring description is ideal to me but it does not work."

[Bob_Y.]

The file created by the Write LVM File is a text file. It sounds like you are trying to write an annotation into the file that cannot be read by someone with just notepad. If this is the case, you might want to use the comment section and modify your string before you write it in and then un modify it after you read it out. This could be done by type casting your string to a U8 and then rotate it a number of bits (say 4) converting it back to a string and sending it to the file. When you read it you do the same thing except you rotate it enough to bring it back to the origional (in this example 4 more bits). This will make it incomprehensible in notepad et al.

As for the description versus the comment, the description is written once in t
he overall header and the comment is written with the data. If you want one annotaion for the whole file, you use the description. If you want a different annotation for each section of data in the file, you use the comment. And it sounds like you know how to open the Express VIs up and modify them to change the description constant into a control.

If I have not given you what you are looking for, please better describe you problem in more detail and we'll take another crack at it.

Good Luck!

[Jeremy_L]

Hi,

If I am not mistaken, usually writing a title to a file means having an annotation in the header. This would then mean that you want to write to the description of the express vi. If you choose to use this, then you do not have access to it as a terminal input on the express VI. So, when you create your lvm file, you have to open the configuration of the express VI and type in the constant. You cannot change this programmatically or wire a string constant or control to it. If you want to have the programmability feature, then you should use the Comment terminal. Hope this clears up the confusion! Please let us know if this is not what you are referring to, and if so provide us with some details and a better explanation. Tha
nks for your patience!

Jeremy L.
National Instruments

[hema]

hello,

I am trying to give a header to the .lvm file in one shot.that is one annotation for the whole file.

My annotaton is for example 'Cyclic Spin Test data' is to be given programatically. I do not want many annotations in the file.

Because there is no Description terminal on the Write LVMExpress, i tried to open the front panel and make description control as one more input.

Then i wired my string constant value to this description terminal, it did not work. So i do not know
how to get this..
Thanks & Regards

[hema]

hello,

I am trying to give a header to the .lvm file in one shot.that is one annotation for the whole file.

My annotaton is for example 'Cyclic Spin Test data' is to be given programatically. I do not want many annotations in the file.

Because there is no Description terminal on the Write LVMExpress, i tried to open the front panel and make description control as one more input.

Then i wired my string constant value to this description terminal, it did not work. So i do not know
how to get this..
Thanks & Regards
hema

[Jeremy_L]

Hi,

If you want to get access to that Description terminal, you will have to open the front panel of the Express VI and convert it to a standard subvi. Once it is a standard subvi, you cannot change it back into an express VI. You lose the configuration settings, and must set those properties yourself by wiring the values to the subvi. Once you have converted the subvi, go into the subvi's block diagram. You'll notice that you have the description terminal wired to a constant. Right click on the constant and change it to a control. Then, go to your front panel and right click on the icon in the upper right corner. Select Show Connector, and connect the new description control to a terminal in the connector pane. Once y
ou have done this, save the VI and then return to your main VI. You should now see that another terminal has been added to the front of the Write LVM subvi. Here, you can see the description. Wire your description (constant or control) to this terminal and you're set. Keep in mind, however, that you lose all functionality of an Express VI, and you now have a subvi if you choose to do this. Hope this helps!

Jeremy L.
National Instruments