File content as of revision 0:4a55d0a21ea9:

#include <PID.h>
#include <stdlib.h>
#include <math.h>
/*Constructor (...)*********************************************************
 *    The parameters specified here are those for for which we can't set up 
 *    reliable defaults, so we need to have the user set them.
 ***************************************************************************/
PID::PID(float* Input, float* Output, float* Setpoint,
        float Kp, float Ki, float Kd)
{
    
    myOutput = Output;
    myInput = Input;
    mySetpoint = Setpoint;

    
    PID::SetOutputLimits(-1000,1000);                //default output limit corresponds to 
                                                //the arduino pwm limits
    PID::SetTunings(Kp, Ki, Kd);
    //PID::SetIntegratorLimits(399);
       
    

}
 
 
/* Compute() **********************************************************************
 *     This, as they say, is where the magic happens.  this function should be called
 *   every time "void loop()" executes.  the function will decide for itself whether a new
 *   pid Output needs to be computed.  returns true when the output is computed,
 *   false when nothing has been done.
 **********************************************************************************/ 
void PID::Compute()
{

    float input = *myInput;
    float error =(*mySetpoint)-input; 
    
    ITerm+= (error+lasterror)/2;
    /*
     if(!ki==0){
    
     if(ITerm < (-abs(max/ki))){
        ITerm= (-abs(max/ki));
        }
     else if(ITerm > abs(max/ki)){
        ITerm= abs(max/ki);
        }
            }
     */  
     float dInput = (error - lasterror);
 

           /*Compute PID Output*/
     float output = (kp * error )+(ki * (ITerm))+(kd * (dInput));
       if(output > outMax) output = outMax;
      else if(output < outMin) output = outMin;
      *myOutput =output;

     /*Remember some variables for next time*/
      lasterror=error;

     
}


/* SetTunings(...)*************************************************************
 * This function allows the controller's dynamic performance to be adjusted. 
 * it's called automatically from the constructor, but tunings can also
 * be adjusted on the fly during normal operation
 ******************************************************************************/ 
void PID::SetTunings(float Kp, float Ki, float Kd)
{
   kp = Kp;
   ki = Ki; 
   kd = Kd; 
//lasterror=0;
//ITerm=0; 
  
}
  
/* SetOutputLimits(...)****************************************************
 *     This function will be used far more often than SetInputLimits.  while
 *  the input to the controller will generally be in the 0-1023 range (which is
 *  the default already,)  the output will be a little different.  maybe they'll
 *  be doing a time window and will need 0-8000 or something.  or maybe they'll
 *  want to clamp it from 0-125.  who knows.  at any rate, that can all be done
 *  here.
 **************************************************************************/
void PID::SetOutputLimits(float Min, float Max)
{
    if(Min >= Max) return;
        outMin = Min;
        outMax = Max;
 
 }
/****************SetIntegratorLimits**********/
void PID::SetIntegratorLimits(float Max)
{
max=Max;
}