Make the external interface "pure"

This removes all internal calls to millis() and puts the
responsibility of getting the millisecond count to the caller.

This change removes the dependency on the Arduino standard library and
allows this code to run on any platform where a millis() function is implemented.

Author: adisbladis

PID_v1.cpp

@@ -5,12 +5,6 @@
  * This Library is licensed under the MIT License
  **********************************************************************************************/
 
-#if ARDUINO >= 100
-#include "Arduino.h"
-#else
-#include "WProgram.h"
-#endif
-
 #include "PID_v1.h"
 
 // The parameters specified here are those for for which we can't set up
@@ -31,8 +25,6 @@ PID::PID(double *Input, double *Output, double *Setpoint, double Kp, double Ki,
 
   PID::SetControllerDirection(ControllerDirection);
   PID::SetTunings(Kp, Ki, Kd, POn);
-
-  lastTime = millis() - SampleTime;
 }
 
 // To allow backwards compatability for v1.1, or for people that just want to
@@ -42,17 +34,23 @@ PID::PID(double *Input, double *Output, double *Setpoint, double Kp, double Ki,
     : PID::PID(Input, Output, Setpoint, Kp, Ki, Kd, P_ON_E,
                ControllerDirection) {}
 
+void PID::Begin(unsigned long now) { lastTime = now - SampleTime; }
+
+void PID::Begin(PIDControllerMode mode, unsigned long now) {
+  Begin(now);
+  SetMode(mode);
+}
+
 // 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.
-bool PID::Compute() {
+bool PID::Compute(unsigned long now) {
   if (mode != AUTOMATIC) {
     return false;
   }
 
-  unsigned long now = millis();
   unsigned long timeChange = (now - lastTime);
   if (timeChange >= SampleTime) {
     /*Compute all the working error variables*/

PID_v1.h

@@ -1,6 +1,4 @@
-#ifndef PID_v1_h
-#define PID_v1_h
-#define LIBRARY_VERSION 1.2.1
+#pragma once
 
 enum PIDControllerDirection { DIRECT, REVERSE };
 enum PIDControllerMode { MANUAL, AUTOMATIC };
@@ -21,14 +19,18 @@ class PID {
   PID(double *, double *, double *, double, double, double,
       PIDControllerDirection);
 
+  // Sets initial state relative to current time
+  void Begin(PIDControllerMode, unsigned long);
+  void Begin(unsigned long);
+
   // sets PID to either Manual (0) or Auto (non-0)
   void SetMode(PIDControllerMode Mode);
 
   // performs the PID calculation.  it should be
   // called every time loop() cycles. ON/OFF and
   // calculation frequency can be set using SetMode
   // SetSampleTime respectively
-  bool Compute();
+  bool Compute(unsigned long);
 
   // clamps the output to a specific range. 0-255 by default, but
   // it's likely the user will want to change this depending on
@@ -94,4 +96,3 @@ class PID {
   unsigned long SampleTime;
   double outMin, outMax;
 };
-#endif

examples/PID_AdaptiveTunings/PID_AdaptiveTunings.ino

@@ -30,7 +30,7 @@ void setup() {
   Setpoint = 100;
 
   // turn the PID on
-  myPID.SetMode(AUTOMATIC);
+  myPID.Begin(AUTOMATIC, millis());
 }
 
 void loop() {
@@ -44,6 +44,6 @@ void loop() {
     myPID.SetTunings(aggKp, aggKi, aggKd);
   }
 
-  myPID.Compute();
+  myPID.Compute(millis());
   analogWrite(PIN_OUTPUT, Output);
 }

examples/PID_Basic/PID_Basic.ino

@@ -13,19 +13,20 @@ double Setpoint, Input, Output;
 
 // Specify the links and initial tuning parameters
 double Kp = 2, Ki = 5, Kd = 1;
-PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);
+PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd,
+          PIDControllerDirection::DIRECT);
 
 void setup() {
   // initialize the variables we're linked to
   Input = analogRead(PIN_INPUT);
   Setpoint = 100;
 
   // turn the PID on
-  myPID.SetMode(AUTOMATIC);
+  myPID.Begin(PIDControllerMode::AUTOMATIC, millis());
 }
 
 void loop() {
   Input = analogRead(PIN_INPUT);
-  myPID.Compute();
+  myPID.Compute(millis());
   analogWrite(PIN_OUTPUT, Output);
 }

examples/PID_PonM/PID_PonM.ino

@@ -24,11 +24,11 @@ void setup() {
   Setpoint = 100;
 
   // turn the PID on
-  myPID.SetMode(PIDControllerMode::AUTOMATIC);
+  myPID.Begin(PIDControllerMode::AUTOMATIC, millis());
 }
 
 void loop() {
   Input = analogRead(0);
-  myPID.Compute();
+  myPID.Compute(millis());
   analogWrite(3, Output);
 }

examples/PID_RelayOutput/PID_RelayOutput.ino

@@ -40,12 +40,12 @@ void setup() {
   myPID.SetOutputLimits(0, WindowSize);
 
   // turn the PID on
-  myPID.SetMode(PIDControllerMode::AUTOMATIC);
+  myPID.Begint(PIDControllerMode::AUTOMATIC, millis());
 }
 
 void loop() {
   Input = analogRead(PIN_INPUT);
-  myPID.Compute();
+  myPID.Compute(millis());
 
   /************************************************
    * turn the output pin on/off based on pid output