MATLAB: Is there a way to directly load the data from a text file into a S-function in Simulink 7.0 (R2007b)

simulink

I have a text file with data and I want to load this data directly into an S-function.

Best Answer

Below are the steps that you can use to read data directly from a text file into Simulink S-function as a source:

1. Specify the sizes and the sample time for the S-function.

2. Open the file by using the FOPEN function in the mdlStart or the mdlInitializeConditions function.

3. Store the pointer in a PWork vector for later use.

4. In the mdlOutputs function, obtain the file pointer from work storage and use the FSCANF to read the next element.

5. Then close the file using the FCLOSE in mdlTerminate.

See the attached simple example model 'test_textSource.mdl' which reads the data from a text file 'input.txt' into an S-function.

Related Solutions

MATLAB: Does the Lookup Table(n-D) block error in Simulink 7.0 (R2007b)

The Lookup Table (n-D) block in Simulink 7.0 (R2007b) does not use a masked S-function underneath. In Simulink 6.6 (R2007a) and previous versions the lookup Table (n-D) had an underlying S-function.

For a later version such as R2007b showing the masked S-function behavior indicates that Simulink is picking up libraries from an earlier version installed in the machine.

As a workaround, please try one of the following:

a) Use SLUPDATE to replace blocks from previous releases with latest versions

b) Make sure that the current version's Simulink libraries are on top in MATLAB path to force Simulink to pick up the new version of the library.

Please execute the following in the MATLAB Command Window:

[matlabroot  '\toolbox\simulink\blocks']

This will return the path of the library blocks in which Lookup tables reside.

Please add this path on top of the existing MATLAB path. To do this, navigate to File -> Set Path-> Add with Sub Folders.

Make sure that this path (which was returned in the Command Window earlier) is placed higher in the path than the older version of Simulink. Then save the path and restart MATLAB.

Simulink should now pick up the newer version of the Lookup table library.

MATLAB: Can I create a C++ MEX-file S-function

We officially support C++ MEX-file S-functions as of Simulink 4.0 (R12).

To view an example of how to do this, please type:

sfundemos

at the MATLAB Command Prompt. This will open sfundemos.mdl. This demo that ships with SIMULINK provides examples of how to write different types of S-Functions and includes a C++ example.

You can also take a look at chapter 4 of the "Writing S-function" manual which has a good description on writing C++ MEX-file S-functions.

When writing the S-function, declare the MEX Function as extern "C". The rest of the code that you write can all be in C++. For example:

 extern "C" 
 {
 void mexFunction(
     int nlhs_,
     mxArray *plhs_[],
     int nrhs_,
     const mxArray *prhs_[])
 {
   /* Body can use all C++ language features and file can be compiled with a
      C++ compiler
    */
 }
 }

Below is the 'Timestwo' example written as a C++ file. You can compile the file using the MEX command. Note that if you are using the Watcom compiler, you need to add the -DNO_BUILT_IN_SUPPORT_FOR_BOOL flag to your COMPFLAGS option in your options file.

If you are using MSVC 5.0, you do not need to add this flag. The C compiler will automatically know to compile it as C++ code using the mex command.

 /*
* TIMESTWO An example C-file S-function for multiplying an input by 2
*      
*      y  = 2*x
*   
*   See sfuntmpl.c for a general S-function template.
*
*   See also VSFUNC, DSFUNC, SFUNTMPL.
* 
*   Copyright (c) 1990-96 by MathWorks, Inc.
*   All Rights Reserved
*   $Revision: 1.1 $
*/
 #ifdef __cplusplus
     extern "C" {
 #endif
 #define S_FUNCTION_NAME timestwo_level1_cpp
 /* The following three lines are necessary for the WATCOM compiler
* only. You need to remove these lines for the MSVC compiler.
*/
 #ifndef COMPILER_SUPPORTS_BOOL
 typedef int bool;
 #endif
 #include "simstruc.h"
 /*
* mdlInitializeSizes - initialize the sizes array
*/
 static void mdlInitializeSizes(SimStruct *S)
 {
     ssSetNumContStates(    S, 0);   /* number of continuous states */
     ssSetNumDiscStates(    S, 0);   /* number of discrete states */
     ssSetNumInputs(        S, DYNAMICALLY_SIZED);   /* number of inputs */
     ssSetNumOutputs(       S, DYNAMICALLY_SIZED);   /* number of outputs */
     ssSetDirectFeedThrough(S, 1);   /* direct feedthrough flag */
     ssSetNumSampleTimes(   S, 1);   /* number of sample times */
     ssSetNumSFcnParams(    S, 0);   /* number of input arguments */
     ssSetNumRWork(         S, 0);   /* number of real work vector elements */
     ssSetNumIWork(         S, 0);   /* number of integer work vector elements */
     ssSetNumPWork(         S, 0);   /* number of pointer work vector elements */
 }
 /*
* mdlInitializeSampleTimes - initialize the sample times array
*/
 static void mdlInitializeSampleTimes(SimStruct *S)
 {
     ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
     ssSetOffsetTime(S, 0, 0.0);
 }
 /*
* mdlInitializeConditions - initialize the states
*/
 static void mdlInitializeConditions(double *x0, SimStruct *S)
 {
 }
 /*
* mdlOutputs - compute the outputs
*/
 static void mdlOutputs(double *y, double *x, double *u, SimStruct *S, int tid)
 {
     class mul2 {
         double            *u;
         double            *y;
         int                width;
     public:
         mul2(double *u_i, double *y_i, int width_i) 
         {
             u = u_i;
             y = y_i;
             width = width_i;
         }
         void output(void) 
         {
             for (int i=0;i<width;i++)
             { 
                 *y++=2.0*(*u++); 
             }
         }
     };
     class mul2 m(u,y,ssGetNumOutputs(S));
     m.output();
 }
 /*
* mdlUpdate - perform action at major integration time step
*/
 static void mdlUpdate(double *x, double *u, SimStruct *S, int tid)
 {
 }
 /*
* mdlDerivatives - compute the derivatives
*/
 static void mdlDerivatives(double *dx, double *x, 
                            double *u, SimStruct *S, int tid)
 {
 }
 /*
* mdlTerminate - called when the simulation is terminated.
*/
 static void mdlTerminate(SimStruct *S)
 {
 }
 #ifdefMATLAB_MEX_FILE    /* Is this file being compiled as a MEX-file? */
 #include "simulink.c"      /* MEX-file interface mechanism */
 #else
 #include "cg_sfun.h"       /* Code generation registration function */
 #endif
 #ifdef __cplusplus
     }
 #endif

Best Answer

Related Solutions

MATLAB: Does the Lookup Table(n-D) block error in Simulink 7.0 (R2007b)

MATLAB: Can I create a C++ MEX-file S-function

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