Stateflow

Calling User-Written C Code Functions

To install your own C code functions for use in Stateflow action language, do the following:

1. From the Tools menu, select the Open (RTW or Simulation) Target dialog.
2. When the Open Target dialog appears, select Target Options.
3. Enter the following:

• Include a header file containing the declarations of your C code functions in the Custom code included at the top of generated code field.
• Specify the source file name containing your C code functions in the Custom source files field.

See Specifying Custom Code Options.

To use your own C code functions in Stateflow action language, follow these guidelines:

• Define a function by its name, any arguments in parentheses, and an optional semicolon.
• String parameters to user-written functions are passed between single quotation marks. For example, func(`string').
• An action can nest function calls.
• An action can invoke functions that return a scalar value (of type double in the case of MATLAB functions and of any type in the case of C user-written functions).

Function Call Transition Action Example

These are example formats of function calls using transition action notation.

If S1 is active, event e occurs, c is true, and the transition destination is determined, then a function call is made to function_name with arg1, arg2, and arg3. The transition action in the transition from S2 to S3 shows a function call nested within another function call.

Function Call State Action Example

These are example formats of function calls using state action notation.

When the default transition into S1 occurs, S1 is marked active and then its entry action, a function call to function_name1 with the specified arguments, is executed and completed. If S2 is active and an event occurs, the during action, a function call to function_name3 with the specified arguments, executes and completes.

Passing Arguments by Reference

A Stateflow action can pass arguments to a user-written function by reference rather than by value. In particular, an action can pass a pointer to a value rather than the value itself. For example, an action could contain the following call

• f(&x);
  

where f is a custom-code C function that expects a pointer to x as an argument.

If x is the name of a data item defined in the Stateflow data dictionary, the following rules apply.

• Do not use pointers to pass data items input from Simulink.

• If you need to pass an input item by reference, for example, an array, assign the item to a local data item and pass the local item by reference.

• If x is a Simulink output data item having a data type other than double, the chart property Use strong data typing with Simulink IO must be on (see Specifying Chart Properties).
• If the data type of x is boolean, the coder option Use bitsets to store state-configuration must be turned off (see Use bitsets for storing state configuration -- Use bitsets for storing state configuration variables. This can significantly reduce the amount of memory required to store the variables. However, it can increase the amount of memory required to store target code if the target processor does not include instructions for manipulating bitsets.).
• If x is an array with its first index property set to 0 (see Array), then the function must be called as follows.

• f(&(x[0]));

  This passes a pointer to the first element of x to the function.

• If x is an array with its first index property set to a nonzero number (for example, 1), the function must be called in the following way:

• f(&(x[1]));

  This passes a pointer to the first element of x to the function.

Calling C Functions

MATLAB Functions and Data