.ModelicaDEVS.FunctionBlocks.Delay

Information

• Create a C++ file containing all the functions that you want to be able to use from Dymola. In the case of our Delay block the file's name is "DEVSdelay.cpp" and it defines several functions among which also the following one:
  
  

  #ifndef DEVSdelay_C
  #define DEVSdelay_C
  #include 
  double ARRu[1000], ARRmu[1000], ARRpu[1000], ARRtime[1000];
  int counterIn=1;
  double getSigmaDint(int counterOut, double tim, double delay){
    if ((counterOut+1)%1000==counterIn){
      return 4e10;
    }else{
      if (ARRtime[counterOut]+delay-tim < 0){
        return counterOut;
      }else{
        return ARRtime[counterOut]+delay-tim;
      }
    }
  }
  [...other functions...]
  #endif
  

  
  
  Note that it is important to protect Dymola from including the C++ file more than once. This is done using the #ifndef and #endif construct.
  
  
• Put the file into the folder Dymola/Source since this is where Dymola looks for the C code.
  
  
• Now it is possible to declare a Modelica function that acts as an interface to the C function.
  As we could see in the above code snippet, the function getSigmaDint() expects three arguments and has a return value. This means we have to declare three input variables and one output value in our Modelica function. The variable declaration section of a function is usually followed by the algorithm section. In the case of an external defined function, this section is replaced by two declarations (lines 6 and 7) that tell Dymola a) that the function is an external one and b) where to find the corresponding C code.
  
  

  1 function getSigmaDint
  2   input Integer counterOut;
  3   input Real tim;
  4   input Real delay;
  5   output Real sigma_o;
  6 external "C";     //instead of the "algorithm" declaration
  7   annotation(Include="#include ");
  8 end getSigmaDint;