Target Language Compiler

Generate Code Using a Wrapper

To create a wrapper for external function my_alg.c, you need to construct a TLC file that embodies its calling function, wrapsfcn.c. The TLC file must generate C code that provides

• A function prototype for the external function that returns a double, and passes the input double u.
• An appropriate function call to my_alg() in the outputs section of the code.

To create a wrapper for my_alg(), do the following:

1. Open the file change_wrapsfcn.tlc in your editor, and add lines of code where comments indicate to create a workable wrapper.
2. Save the edited file as wrapsfcn.tlc. It must have the same name as the S-function block that uses it or the TLC won't be called to inline code.
3. Inform Simulink that your code has an external reference to be resolved. To update the model's parameters, in the MATLAB command window type

• set_param('externalcode/S-Function','SFunctionModules','my_alg')
  

4. Click Build Model (or type Ctrl+B) to create the stand-alone application.
5. If all went well, run the new stand-alone application and verify that it yields identical results as prior executions:

• !externalcode
  

If you had any problems building the application:

• Find the error messages and try to determine what files are at fault, paying attention to which step (code generation, compiling, linking) failed.
• Be sure you issued the set_param() command as specified above.
• Chances are that any problems can be traced to your TLC file. It may be helpful to use the TLC debugger to step through wrapsfcn.tlc.

As a last resort, look at wrapsfcn.tlc in the solutions/tlc_solution directory, also listed below:

• %% File    : wrapsfcn.tlc
  %% Abstract:
  %%      Example tlc file for S-function wrapsfcn.c
  %%
  %% Copyright 1994-2001 The MathWorks, Inc.
  %%
  %% $ Revision: 1.3 $
  
  %implements "wrapsfcn" "C"
  
  %% Function: BlockTypeSetup ================================
  %% Abstract:
  %%      Create function prototype in model.h as:
  %%      "extern double my_alg(double u);" 
  %%
  %function BlockTypeSetup(block, system) void
    %openfile buffer
    %% ASSIGNMENT: PROVIDE ONE LINE OF CODE AS A FUNCTION PROTOTYPE
    %% FOR "my_alg" AS DESCRIBED IN THE WRAPPER TLC ASSIGNMENT 
    extern double my_alg(double u);
  
    %closefile buffer
    %<LibCacheFunctionPrototype(buffer)>
  %endfunction %% BlockTypeSetup
  
  
  %% Function: Outputs =======================================
  %% Abstract:
  %%      y = my_alg( u );
  %%
  %function Outputs(block, system) Output
    /* %<Type> Block: %<Name> */
    %assign u = LibBlockInputSignal(0, "", "", 0)
    %assign y = LibBlockOutputSignal(0, "", "", 0)
    %% PROVIDE THE CALLING STATEMENT FOR "wrapfcn"
    %<y> = my_alg( %<u> );
  
  %endfunction %% Outputs
  

Look at the highlighted lines. Did you declare my_alg() as extern double? Did you call my_alg() with the proper input and output? Correct any mistakes you may have made and build the model again.

Generate Code Without a Wrapper

Code Generation Architecture