File content as of revision 4:a51fa881cc4c:

#include "mbed.h"
#ifndef PID_H_
#define PID_H_

class PID
{
  public:
 
  //Constants used in some of the functions below
  #define AUTOMATIC 1
  #define MANUAL    0
  #define DIRECT  0
  #define REVERSE  1
 
  //commonly used functions **************************************************************************
    PID(double*, double*, double*,        // * constructor.  links the PID to the Input, Output, and 
        double, double, double, int);     //   Setpoint.  Initial tuning parameters are also set here
    
    void SetMode(int Mode);               // * sets PID to either Manual (0) or Auto (non-0)
 
    bool Compute();                       // * performs the PID calculation.  it should be
                                          //   called every time loop() cycles. ON/OFF and
                                          //   calculation frequency can be set using SetMode
                                          //   SetSampleTime respectively
 
    void SetOutputLimits(double, double); //clamps the output to a specific range. 0-255 by default, but
                                          //it's likely the user will want to change this depending on
                                          //the application
    
 
 
  //available but not commonly used functions ********************************************************
    void SetTunings(double, double,       // * While most users will set the tunings once in the 
                    double);              //   constructor, this function gives the user the option
                                          //   of changing tunings during runtime for Adaptive control
    void SetControllerDirection(int);     // * Sets the Direction, or "Action" of the controller. DIRECT
                                          //   means the output will increase when error is positive. REVERSE
                                          //   means the opposite.  it's very unlikely that this will be needed
                                          //   once it is set in the constructor.
    void SetSampleTime(int);              // * sets the frequency, in Milliseconds, with which 
                                          //   the PID calculation is performed.  default is 100
                                          
   // void changeSetpoint(*double);         // changes system setpoint                                      
                                          
  //Display functions ****************************************************************
    double GetKp();                       // These functions query the pid for interal values.
    double GetKi();                       //  they were created mainly for the pid front-end,
    double GetKd();                       // where it's important to know what is actually 
    int GetMode();                        //  inside the PID.
    int GetDirection();                   //
 
  private:
    void Initialize();
    
    double dispKp;              // * we'll hold on to the tuning parameters in user-entered 
    double dispKi;              //   format for display purposes
    double dispKd;              //
    
    double kp;                  // * (P)roportional Tuning Parameter
    double ki;                  // * (I)ntegral Tuning Parameter
    double kd;                  // * (D)erivative Tuning Parameter
 
    int controllerDirection;
 
    double *myInput;              // * Pointers to the Input, Output, and Setpoint variables
    double *myOutput;             //   This creates a hard link between the variables and the 
    double *mySetpoint;           //   PID, freeing the user from having to constantly tell us
                                  //   what these values are.  with pointers we'll just know.
              
    unsigned long lastTime;
    double ITerm, lastInput;
 
    unsigned long SampleTime;
    double outMin, outMax;
    bool inAuto;
    Timer t;
};

#endif