Motorola DSP Developer's Kit

Instantiating Input and Output Objects

Mapping Arguments to Objects.   

To instantiate input and output objects you should use the macros defined as CREATE_INPUT_ARG and CREATE_OUTPUT_ARG in the <matlab>/toolbox/motdsp/motdspmex/include/headers/56k/motdsp_api.h file. Also, CREATE_NORM_INPUT_ARG is available if you are sure that the input will always be normalized. See Chapter 3, Motorola DSP MEX-File Programming Reference.

For example,

CREATE_INPUT_ARG(a, 0);
CREATE_INPUT_ARG(b, 1);
num_data_inputs = config.GetFixedInputs();
    if (num_data_inputs == 2)        // i.e., two Matlab inputs
    {           
        / REAL conditions...
        if ((a->GetType() == REAL_DOUBLE) && 
                    (b->GetType() == REAL_DOUBLE)) 
        {
            CREATE_OUTPUT_ARG(y, 0, REAL_DOUBLE);
        }
    }

Once the mapping of arguments to objects is complete, all access to the MEX-file arguments is through these newly created objects (i.e., the input objects a and b, and output object y in this example).

Mapping String Arguments..   

For advanced MEX-files, use the CREATE_OPT_INPUT_ARG macro to create input objects from optional string input variables. For example, a filter function may require string inputs as optional arguments to indicate a high-pass or low-pass filter type. Implement this functionality by using code similar to

MOTDSP_Input* c = PTR_NIL;
...
try {
    // Validation Code goes here - see template
    ...
    char *opts[] = {'high', 'low'};
    int num_opts = sizeof(opts)/sizeof(opts[0]);
    // Instantiate the optional string arguments
    CREATE_OPT_INPUT_ARG(c,2,opts,num_opts);
    // The 2 indicates that the optional string input 
    // is mapped from position 2 -- i.e. it is the third argument
    // expected on the command line.
    ...
    // To use the optional string inputs.
    // They are treated as fixed inputs...
    if (config.GetFixedInputs()==3) {
         // This suggest there are three input arguments -- NOT
         // including the possible OPTIONAL arguments; DSP type
         // or command file 
         // strings that may be included on the command line.
         if (*(c->GetData()) == 0) {
         // This suggests an input of 'high'
         // Some useful code goes here ...
        }
        if (*(c->GetData()) == 1) {
         // This suggests an input of 'low'
         // Some more useful code goes here ...
        }
        else {
         // Error in string input arg
         // Throw an exception here ...
         sprintf(err_msg, "Invalid string input argument\n");
         THROW_MEX_ERROR(err_msg);
        } 
    }
}

Declaring Input and Output Objects

Instantiating the Motorola DSP Simulator