Allow to set the resolution to either microseconds or microseconds

PID_v1/PID_v1.cpp

@@ -34,7 +34,7 @@ PID::PID(double* Input, double* Output, double* Setpoint,
     PID::SetControllerDirection(ControllerDirection);
     PID::SetTunings(Kp, Ki, Kd);
 
-    lastTime = millis()-SampleTime;				
+    PID::setResolution(MILLIS); // Use a resolution of milliseconds by default
 }
  
  
@@ -47,7 +47,7 @@ PID::PID(double* Input, double* Output, double* Setpoint,
 bool PID::Compute()
 {
    if(!inAuto) return false;
-   unsigned long now = millis();
+   unsigned long now = PID::getTime();
    unsigned long timeChange = (now - lastTime);
    if(timeChange>=SampleTime)
    {
@@ -86,7 +86,7 @@ void PID::SetTunings(double Kp, double Ki, double Kd)
  
    dispKp = Kp; dispKi = Ki; dispKd = Kd;
 
-   double SampleTimeInSec = ((double)SampleTime)/1000;  
+    double SampleTimeInSec = ((double)SampleTime)/secondsDivider;  
     kp = Kp;
     ki = Ki * SampleTimeInSec;
     kd = Kd / SampleTimeInSec;
@@ -182,6 +182,29 @@ void PID::SetControllerDirection(int Direction)
    controllerDirection = Direction;
 }
 
+/* getTime()*******************************************************************
+ * Will get the current time either by using millis() or micros()
+ ******************************************************************************/
+unsigned long PID::getTime()
+{
+  if (secondsDivider == 1000.0) return millis();
+  return micros();
+}
+
+/* setResolution(...)**********************************************************
+ * Will set the resolution of getTime().
+ * MILLIS will set the resolution to milliseconds while
+ * MICROS will set the resolution to microseconds.
+ ******************************************************************************/
+void PID::setResolution(int resolution)
+{
+  if (resolution == MILLIS)
+    secondsDivider = 1000.0;
+  else
+    secondsDivider = 1000000.0;
+  lastTime = PID::getTime()-SampleTime; // Update last time variable
+}
+
 /* Status Funcions*************************************************************
  * Just because you set the Kp=-1 doesn't mean it actually happened.  these
  * functions query the internal state of the PID.  they're here for display 

PID_v1/PID_v1.h

@@ -13,6 +13,8 @@ class PID
   #define MANUAL	0
   #define DIRECT  0
   #define REVERSE  1
+  #define MILLIS  0
+  #define MICROS  1
 
   //commonly used functions **************************************************************************
     PID(double*, double*, double*,        // * constructor.  links the PID to the Input, Output, and 
@@ -41,6 +43,9 @@ class PID
 										  //   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 setResolution(int);			  // * Set the resolution of the getTime() function. 
+    									  //   MILLIS sets the resolution to milliseconds.
+    									  //   MICROS sets the resolution to microseconds.
 										  
 										  
 										  
@@ -53,6 +58,8 @@ class PID
 
   private:
 	void Initialize();
+	unsigned long getTime();    // * This will call either millis() or micros()
+	                            //   depending on the used resolution.
 	
 	double dispKp;				// * we'll hold on to the tuning parameters in user-entered 
 	double dispKi;				//   format for display purposes
@@ -73,6 +80,7 @@ class PID
 	double ITerm, lastInput;
 
 	unsigned long SampleTime;
+	double secondsDivider;
 	double outMin, outMax;
 	bool inAuto;
 };