{

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

//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;