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File Reader VI

Module by: National Instruments

Summary: In this exercise, the objective is to build a VI that reads data from a file. Complete the following steps to build a VI that reads the file created previously and displays the information in a string indicator.

Problem 1

1.a) Front Panel

  1. Open a blank VI and build the front panel shown in Figure 1 using the file path control located on the Controls>>Text Controls palette and a string indicator located on the Controls>>Text Indicators palette.
    filereader.png
    Figure 1

1.b) Block Diagram

  1. Build the block diagram shown in Figure 2.
    filereaderbd.png
    Figure 2
    1. OpenFileIcon.png Place the Open/Create/Replace File VI, located on the Functions>>All Functions>>File I/O palette, on the block diagram. This VI displays a dialog box that you use to open or create a file. Right-click the prompt input, select Create>>Constant from the shortcut menu, and type Select Filename in the constant. Right-click the function input, select Create>>Constant from the shortcut menu, and click the constant with the Operating tool to select open.
    2. ReadFileIcon.png Place the Read File function, located on the Functions>>All Functions>>File I/O palette, on the block diagram. This function reads count bytes of data from the file starting at the beginning of the file.
    3. CloseFileIcon.png Place the Close File function, located on the Functions>>All Functions>>File I/O palette, on the block diagram. This function closes the file.
    4. Error.png Place the Simple Error Handler VI, located on the Functions>>All Functions>>Time & Dialog palette, on the block diagram. This VI checks the error cluster and displays a dialog box if an error occurs.
    5. Complete the block diagram as shown in Figure 2.
  2. Save the VI as File Reader.vi in the C:\Exercises\LabVIEW Basics I directory.

1.c) Run the VI

  1. Display the front panel and use the Operating tool to click the Browse button in the path control.
  2. Navigate to demofile.txt and click the Open or OK button.
  3. Run the VI. String Read from File displays the contents of the file.
  4. If time permits, complete the challenge step. Otherwise, save and close the VI.

1.d) Challenge

  1. Modify the VI so it parses the numeric value and displays the numeric value in a numeric indicator. After you finish, save and close the VI.
    tip: Use the Match Pattern function to search for the first numeric character.

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