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Labview programming basics Tutorial-text and complex File I/O

This Labview programming language tutorial covers File I/O in labview. It covers text and numeric based file formats. This labview tutorial covers following topics:
Labview data types
Creating SubVI
Creating Array and Array operations
Cluster concepts in labview
Various plots in labview
File I/Os
For loop,while loop and case structure
Local variable vs Global variable concepts

File I/O is used to pass data between your VI and certain data files.

The file I/O operations allow the user to perform any of the following:

•  Opening and closing data files
•  Reading from or writing to files including spreadsheets
•  Managing files (moving, renaming, or changing file characteristics)
•  Managing configuration files (creating, modifying, and reading)

Two types of file I/O VIs exist:

High-Level: performs common I/O operations all in one VI (i.e. opens, reads, and closes file).

1) These VIs can be accessed in the Functions Palette: •  Functions Palette -> File I/O

2) These VIs can perform operations from the following data types:
•  Characters to and from text files
•  Lines from text files
•  Arrays of single-precision numerics to and from spreadsheet text files
•  Arrays of single-precision numerics or signed 16-bit integers to and from binary files

3)Pls. donot put low level vis in the loops and not high level one.

4) High-level VIs always need a file path input and if one is not assigned, an error message will appear prompting for the file path.

Low-Level: performs only one I/O operation (i.e. reads file)
File I/O formats depend on the type of files being used. 3 types of formats exist: text, binary, and datalog. Some basic guidelines for choosing a data type are:

•  Text files are the most common and should be used if the data will be used in programs such as Word and Excel.

•  Binary files are more efficient than text files with respect to disk space and speed and should be used if memory and speed is crucial.

•  Datalog files are the best way to store data if the data will only be accessed in LabVIEW and if the data structure is complex.

Using File I/O in labview VI

Access File I/O operations by:

•  Functions Palette -> All-Functions -> File I/O

•  In addition to the File I/O operations, the user will need to identify the File Path so that the VI knows where the file can be accessed. Insert a File Path Control or Indicator by:

•  Controls Palette -> All-Controls -> String & Path -> File Path Control or File Path Indicator


text file I/O block digram

EXAMPLE BLOCK DIAGRAM of Numeric complex FILE I/O labview VI

Following labview VI is used to read numeric file data into labview and stores them to array. Note that text file need to have numeric data separated by tab space for multiple columns(if any). It also explains how complex data is read into labview using file I/O and array index. The complex data to be read should be separated into real and imaginary and need to store in a text file. Both real and image columns should be separated by tab space. The file I/O reads this complex data and array index in labview separates both real and imag part. This real and imag data is further combined into complex array in labview, which can be processed as desired.

numeric file I/O block digram

Download Labview Source code of this FILE I/O example

Download TEXT FILE IO example labview VI
Download Numeric FILE IO example labview VI
Download 2D array IQ file numeric

Related Links

•   What is Labview
•   National Instruments Labview
•   Download Labview, http://www.ni.com/downloads/products/


Useful Links to Labview Source codes

Refer following as well as links mentioned on left side panel for useful labview source codes.

Hex to Binary labview VI      Decimal to Binary labview VI
Number Generator labview VI      Binary to Decimal labview VI
Binary number generator     modulator-demodulator
FFT     up and down sample

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