Integrate Custom Structures in Stateflow Charts

You can define custom structures in C code, which you can integrate with your Stateflow^® chart in a Simulink^® model for simulation and code generation. For example, the model sf_bus_demo uses a custom C function to write to the output structure outbus. By sharing data with custom code, you can augment the capabilities supported by Stateflow and take advantage of your preexisting code. For more information, see Reuse Custom Code in Stateflow Charts and Access Bus Signals Through Stateflow Structures.

Define Custom Structures in C Code

In your C code, define a structure by creating a custom header file. The header file contains typedef declarations matching the properties of the Simulink.Bus object that defines the Stateflow structure. For example, in the model sfbus_demo, the header file counterbus.h declares three custom structures:
```
...
typedef struct {
  int input;
} SIGNALBUS;

typedef struct {
  int upper_saturation_limit;
  int lower_saturation_limit;
} LIMITBUS;

typedef struct {
  SIGNALBUS inputsignal;
  LIMITBUS limits;
} COUNTERBUS;
...
```
In the Bus Editor, define a Simulink.Bus object that matches each custom structure typedef declaration. In the Header file field of each Simulink.Bus object, enter the name of the header file that contains the matching typedef declaration.
Configure your C action language chart to include custom C code.
- To include custom code for simulation, see Access Custom C Code in Nonlibrary Charts.
- To include custom code for code generation, see Integrate External Code by Using Model Configuration Parameters (Simulink Coder).
Build and run your model.

Pass Stateflow Structures to Custom Code

When you write custom code functions that take structure pointers as arguments, pass the Stateflow structures by address. To pass the address of a Stateflow structure or one of its fields to a custom function, use the & operator and dot notation:

&outbus provides the address of the Stateflow structure outbus.
&outbus.inputsignal provides the address of the substructure inputsignal of the structure outbus.
&outbus.inputsignal.input provides the address of the field input of the substructure outbus.inputsignal.

For more information, see Index Substructures and Fields.

For instance, the model sfbus_demo contains a custom C function counterbusFcn that takes structure pointers as arguments. The custom header file contains this function declaration:

extern void counterbusFcn
            (COUNTERBUS *u1, int u2, COUNTERBUS *y1, int *y2);

The chart passes the addresses to the Stateflow structures counterbus_struct and outbus by using this function call:

counterbusFcn(&counterbus_struct, u2, &outbus, &y2);

The function reads the value of the chart input u2 and the local structure counterbus_struct. It writes to the chart output y2 and the output structure outbus.

Documentation