Custom Data Types in C S-Functions

C S-Functions can communicate using user-defined data types. There are two broad categories for these data types:

Using Simulink Recognizable Data Types in C S-Functions

To register a custom data type recognizable by Simulink, the S-function mdlInitializeSizes routine must register the data type, using ssRegisterTypeFromNamedObject.

For example, the following code placed at the beginning of mdlInitializeSizes defines a custom data type from a Simulink.AliasType object named u8 in the MATLAB^® workspace. The example then assigns the custom data type to the first output port.

int id1;
ssRegisterTypeFromNamedObject(S, "u8", &id1);
ssSetOutputPortDataType(S, 0, id1);

In addition, you can use the identifier id1 to assign this data type to S-function parameters, DWork vectors, and input ports.

Using Opaque Data Types in C S-Functions

For cases in which S-Functions need to communicate using a data type that cannot be understood by Simulink, the S-function mdlInitializeSizes routine must:

Define the user-defined data type in an external header file to include in the level 2 C S-Function.

/* Define the structure of the user-defined data type */
typedef struct{
    int8_T   a;
    uint16_T b;
}myStruct;

Place the following code at the beginning of mdlInitializeSizes to set the size and zero representation of the custom data type myStruct.

/* Define variables */
int_T   status;
DTypeId  id;

myStruct tmp;

/* Register the user-defined data types */
id = ssRegisterDataType(S, "myStruct");
if(id == INVALID_DTYPE_ID) return;

/* Set the size of the user-defined data type */
status = ssSetDataTypeSize(S, id, sizeof(tmp));
if(status == 0) return;

/* Set the zero representation */
tmp.a = 0;
tmp.b = 1;
status = ssSetDataTypeZero(S, id, &tmp);