MATLAB: S-function and input data

simulink

Hello! I have a little s-function. I want to use input data in void spinDisplay(void). But this function must be void. How can I do that? Thank for any answer. Natalia
    #define S_FUNCTION_NAME  timestwo
    #define S_FUNCTION_LEVEL 2
    #include "simstruc.h"
    #include <GL/glut.h>
    #include <stdlib.h>
    static GLfloat spin = 0.0;
    static GLfloat k = 0.0;
    void display(void)
    {
       glClear(GL_COLOR_BUFFER_BIT);
       glPushMatrix();
       glRotatef(spin, 0.0, 0.0, 1.0);
       glColor3f(1.0, 1.0, 1.0);
       glRectf(-25.0, -25.0, 25.0, 25.0);
       glPopMatrix();
       glutSwapBuffers();
    }
    void spinDisplay(void)
    {
          spin = k;
       if (spin > 360.0)
          spin = spin - 360.0;
       glutPostRedisplay();
    }
    void init(void) 
    {
       glClearColor (0.0, 0.0, 0.0, 0.0);
       glShadeModel (GL_FLAT);
    }
    void reshape(int w, int h)
    {
       glViewport (0, 0, (GLsizei) w, (GLsizei) h);
       glMatrixMode(GL_PROJECTION);
       glLoadIdentity();
       glOrtho(-50.0, 50.0, -50.0, 50.0, -1.0, 1.0);
       glMatrixMode(GL_MODELVIEW);
       glLoadIdentity();
    }
    static void mdlInitializeSizes(SimStruct *S)
    {
        ssSetNumSFcnParams(S, 0);
        if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
            return; /* Parameter mismatch will be reported by Simulink */
        }
        if (!ssSetNumInputPorts(S, 1)) return;
        ssSetInputPortWidth(S, 0, DYNAMICALLY_SIZED);
        ssSetInputPortDirectFeedThrough(S, 0, 1);
        if (!ssSetNumOutputPorts(S,1)) return;
        ssSetOutputPortWidth(S, 0, DYNAMICALLY_SIZED);
        ssSetNumSampleTimes(S, 1);
        /* specify the sim state compliance to be same as a built-in block */
        ssSetSimStateCompliance(S, USE_DEFAULT_SIM_STATE);
        /* Take care when specifying exception free code - see sfuntmpl_doc.c */
        ssSetOptions(S,
                     SS_OPTION_WORKS_WITH_CODE_REUSE |
                     SS_OPTION_EXCEPTION_FREE_CODE |
                     SS_OPTION_USE_TLC_WITH_ACCELERATOR);
    }
    static void mdlInitializeSampleTimes(SimStruct *S)
    {
        ssSetSampleTime(S, 0, INHERITED_SAMPLE_TIME);
        ssSetOffsetTime(S, 0, 0.0);
        ssSetModelReferenceSampleTimeDefaultInheritance(S); 
    }
    static void mdlOutputs(SimStruct *S, int_T tid)
    {   
       glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
       glutInitWindowSize (250, 250); 
       glutInitWindowPosition (100, 100);
       glutCreateWindow ("hello");
       init ();
       glutDisplayFunc(display); 
       glutReshapeFunc(reshape); 
       glutIdleFunc(spinDisplay);
       glutMainLoop();
        }
    }
    #ifdef  MATLAB_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

Best Answer

To access the S-function input data, you need to have access to the Simstruct pointer (the S argument in all S-function callback methods), which needs to be passed in.
At best, you can have a global variable to cache the pointer to the input signal that you could update right before calling spinDisplay(). Note that global data is shared if you have multiple instances of the S-function in your model, so you must only use it to cache the pointer just before calling your function.
I'm not entirely confident that this is the best solution, but there's an idea for you to try.
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