Listing 3: Derived-class functions for PID Control

PipingSet::PipingSet( double kP, double kI, double kD,
                      double lI, double cD) :
    PidControl( kP, kI, kD, lI, cD )
{
   CurrentMode = PIPE_MEASURE;
   mbox = OSMboxCreate( (void*) 0 );
   OSTaskCreate( (void(*) (void*))PipingSet::StartControlTask,
                 (void *)this, &TaskStack[CONTROL_STACK_SIZE],
                 PD_CONTROL_PRIO );
}
//-----------------------------------------------------------------
void PipingSet::SetSetpoint( double SetPoint )
{

   OSMboxPost( mbox, (void*)CHANGE_SETPOINT_START );
   PidControl::SetSetpoint( ( SetPoint / FullScale ) * 100 );
   OSMboxPost( mbox, (void*)SETPOINT_COMPLETE );
}
//-----------------------------------------------------------------
void PipingSet::ControlTask( void )
{
   UBYTE err;
   double pressure;
   int    stop_control;
   double gain;
   float  volts;
   void   *msg;
   for(;;) {
      msg = OSMboxPend( mbox, 0, &err );
      if( (int ) msg == START_CONTROL ) {
         CurrentMode = PIPE_CONTROL;
         stop_control = FALSE;
         while( !stop_control ) {
            pressure = controlSensor->get_pressure();
            gain = CalculateGain( ( pressure / FullScale ) * 100 );
            volts = -( gain / 100 );
            if( volts > 10 )
                volts = 10;
            else if( volts < -10 )
                volts = -10;
            SetServoVoltage( volts );
            msg = OSMboxPend( mbox, 1, &err );
            if( err == OS_NO_ERR ) {
               if( (int)msg == STOP_CONTROL ) {
                  SetServoVoltage( 0.0 );
                  stop_control = true;
                  }
               else if( (int)msg == CHANGE_SETPOINT_START ) {
                  do
                     msg = OSMboxPend( mbox, 0, &err );
                     while( (int)msg != SETPOINT_COMPLETE );
                  }
               }
            }
         CurrentMode = PIPE_MEASURE;
         }
      }
}
//End of File