modelParameters = Simulink.Parameter;
modelParameters.Value = myStruct;
modelParameters.CoderInfo.StorageClass = 'ExportedGlobal';

modelParameters_T *modelParameters = (modelParameters_T*)mxGetPr(ssGetSFcnParam(S, PARAM_STRUCT));

mxArray* param = ssGetSFcnParam(S, PARAM_STRUCT);
mxArray* prop = mxGetProperty(param, 0, "Value"); // Get Value property from param object
// If prop is double precision use the following line to get its value
double* prop = *(mxGetPr(prop));