Update PID_v1.cpp

I put the start sample time  at is beginning not after the calculus.
Taking account the calcul past time and other...

PID_v1.cpp

@@ -62,6 +62,8 @@ bool PID::Compute()
    unsigned long timeChange = (now - lastTime);
    if(timeChange>=SampleTime)
    {
+      // take the start sample time		   
+      lastTime = now;	   
       /*Compute all the working error variables*/
       double input = *myInput;
       double error = *mySetpoint - input;
@@ -88,7 +90,7 @@ bool PID::Compute()
 
       /*Remember some variables for next time*/
       lastInput = input;
-      lastTime = now;
+
 	    return true;
    }
    else return false;