Question

I’m trying to create a level 2 S-Function written in C that has different numbers of output ports depending on the signals’ datatypes that are connected to the inports.

The practical background is that I have some other S-Functions that define custom datatypes by calling ssRegisterDataType. These datatypes describe pointers to certain data.

I now want to have another S-Function that can consume these custom datatypes (pointers) and, depending on what pointer type is fed into them, output certain data.

I tried setting the number of output ports through ssSetNumOutputPorts by

static void mdlSetInputPortDataType(SimStruct *S, int portIndex,DTypeId dType)
{
    if( portIndex == 0 )
    {
        if(      dType == ssGetDataTypeId(S, "ptrtype1" ) )
        {
            if (!ssSetNumOutputPorts(S, nOutportsPtr1)) return;
        }
        else if( dType == ssGetDataTypeId(S, "ptrtype2" ) )
        {
            if (!ssSetNumOutputPorts(S, nOutportsPtr2)) return;
        }
        else if( dType == ssGetDataTypeId(S, "ptrtype3" ) )
        {
            if (!ssSetNumOutputPorts(S, nOutportsPtr3)) return;
        }
        else if( dType == ssGetDataTypeId(S, "ptrtype4" ) ) 
        {
            if (!ssSetNumOutputPorts(S, nOutportsPtr4)) return;
        }
        else
        {
            ssSetErrorStatus(S, "Input data type is not supported."); return;
        }


        if (!ssSetInputPortDataType(S, portIndex, dType)) return;
    }
} /* mdlSetInputPortDataType */

while in mdlInitializeSizes I set the inport’s data type to be DYNAMICALLY_TYPED.

But Simulink keeps telling me I should set the inport data type in mdlSetInputPortDataType on a call to ssSetNumOutputPorts. I assume inside this function only the data type of inports may be changed.

Does anybody know of a solution to this problem? The only workaround I can think of is masking the S-Function and having the user to manually select the pointer type that he wishes to be processed. With data type propagation this seems messy and unnecessary though.

Answer 1

You need to set number of ports in mdlInitializeSizes. You cannot change that after that function. The only workaround is the one you mentioned.