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File I/O C S-function Example

version 1.0.0.1 (9.22 KB) by

A simple C S-function which reads data from a file during simulation.

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S-functions are used to create user defined blocks in Simulink. This S-function creates a block that reads data from a file incrementally at each time step of the Simulink simulation.
The S-function was written in C and uses the standard file I/O functions from the stdio.h library (fopen, fscanf, fclose). It is intended merely as an example.

The trickiest part of writing S-functions can sometimes be maintaining persistent data in subsequent calls to the S-function. This issue presents itself in this example. In order to read from the file throughout the simulation without closing and reopening the file each time step, the FILE pointer is stored in the PWork vector. This gives the S-function access to the FILE pointer at each step in the simulation.

In this S-function, the mdlStart function opens the file at the start of the simulation and the mdlTerminate function closes the file at the end. The mdlOutputs function is used to read data from the file at every time step.

To run the example:
1) Enter
mex -setup
at the MATLAB Command Prompt and select a compiler
2) Copy the attached files to the current MATLAB directory
3) Enter
mex cfileiosfun.c
to compile the S-function
4) Open the attached model and simulate.

Comments and Ratings (4)

Ravi

Ravi (view profile)

if i run this simulation..error is
==> mex at 222
unable to complete successfully...

Can you explain.... plzz its urgent.

Thanks in advance

H. Grutzeck

Unfortunately c-Code has poor documentation.
So its difficult for beginners to understand
whats happening

Deepa Jain

sae Yong Lee

Good as an example for s-function beginers

Updates

1.0.0.1

Updated license

MATLAB Release
MATLAB 7.3 (R2006b)

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