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Navigation: Language Reference > Functions > External > dll |
  
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y = dll(filename, functionname, x);
Given a function (functionname) of a dll (filename), the dll function returns the output values (y) for a given input (x).
Users can write their own source code using a native compiler such as Visual C++ or Borland C++. With these compilers it is possible to create DLLs with user defined functions that have an input- output relation which can be embedded in simulation code.
parameters
string filename = 'example.dll';
string function = 'myFunction';
variables
real x[2], y[2];
equations
x = [ramp(1); ramp(2)];
y = dll(filename, function, x);
filename and functionname must be string parameters. Note that the size of Y and X (scalars or matrices) must correspond with the size that is expected for the given dll-function.
20-sim uses the following search order for the dll-file:
| 1. | The bin directory of 20-sim (usually C:\Program Files\20-sim 5.1\bin). |
| 2. | The current directory. |
| 3. | A directory that is entered in list of paths in the General Properties dialog (choose Tools - Options - Folders - DLL Search Paths). Use this option to store DLL's in a central location. |
| 4. | The Windows system directory. |
| 5. | The Windows directory. |
| 6. | The directories that are listed in the PATH environment variable. |
The simplest place to put the DLL-file is the bin directory, but it is always possible to give a complete path for the DLL filename.
20-sim allows for code generation of the 20-sim model. In case of a DLL call, 20-sim cannot generate the complete code for a DLL call since it only knows the DLL file name, function name and arguments and not the internal DLL code.
Therefore, in the generated code, the dll(dll_name, function_name, in) will be generated as:
%dll_name%_%function_name%(double *inarr, int inputs, double *outarr, int outputs, int major)
Where %dll_name% and %function_name% are replaced with the actual DLL and function name. You have to add the C-code implementation of this function yourself to the generated code before you can compile it.