Software Integration

Finally, to bring all these radio environment and navigation control functions in this document all together, they are called from the following overall navigation function which should be called regularly every 200 milliseconds. As an exercise, this function has been headed as a timer call-back function to be called by a designated system timer within a Microsoft Windows environment. 
WORD FAR PASCAL Nav (    //called every 200 ms
  HWND hWnd,             //identifies the Nav window
  WORD wMsg,             //timer message resulting in this call
  int nIDEvent,          //id number of system timer which made the call
  DWORD dwTimer          //current system time
) {
  StnPoll();             //check rough distance of stations
  RxInput();             //scan receiver tuner inputs etc.
  TxScan();              //get station signal strengths

  //The NAV Rx which is currently switched to the NAV computer
  struct RxData *r = *(*(Rx + 4) + Air.Sw);

  struct TxData *t = r->t ;    //dominant station currently being received
  double et = ElapsedTime();   //elapsed time since last pass
  if((int Sig = r->Sig) > 0)   //if in range of nav station
    HorzSteer(t, r, et);       //do horizontal (roll) steering

  //If it is an ILS or ILS/DME and it is within glideslope range
  if(((int st = t->StnType) == 4 || st == 5) && (Sig > 85))
    VertSteer(t, r, et);       //do vertical (pitch) steering
}
For this to work you will have to set up the timer in the WM_CREATE case in the application's MainWndProc() as follows:

'C' Functions

The following schematic shows the relationships between the 'C' functions which have been discussed in these research project notes.

Circuit Breaker Logic

Within the functions discussed in these notes, many of the computations have been made conditional upon the states of various circuit breakers which control the power supplies to the various elements of the aircraft's on-board equipment. The positioning of these circuit breakers is indicated in the diagram below:

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