#include	<PID_v2.h>

const	int	photores	=	A0;	//	Photo	resistor	input
const	int	pot	=	A1;	//	Potentiometer	input
const	int	led	=	9;	//	LED	output	
double	lightLevel;	//	variable	that	stores	the	incoming	light	level
//	Tuning	parameters
float	Kp=0;	//Initial	Proportional	Gain
float	Ki=10;	//Initial	Integral	Gain
float	Kd=0;	//Initial	Differential	Gain
double	Setpoint,	Input,	Output;	//These	are	just	variables	for	storingvalues	
PID	myPID(&Input,	&Output,	&Setpoint,	Kp,	Ki,	Kd,	DIRECT);	
 //	This	sets	up	our	PDID	Loop
 //Input	is	our	PV
//Output	is	our	u(t)
 //Setpoint	is	our	SP
const	int	sampleRate	=	1;	//	Variable	that	determines	how	fast	our	PID	loop	runs	
//	Communication	setup
const	long	serialPing	=	500;	//This	determines	how	often	we	ping	our	loop	
//	Serial	pingback	interval	in	milliseconds	
unsigned	long	now	=	0;	//This	variable	is	used	to	keep	track	of	time	
//	placeholder	for	current	timestamp
unsigned	long	lastMessage	=	0;	//This	keeps	track	of	when	our	loop	last	spoke	to	serial
//	last	message	timestamp.	

void setup() {
  // put your setup code here, to run once:
lightLevel	=	analogRead(photores);//Read	in	light	level
Input	=	map(lightLevel,	0,	1024,	0,	255);		//Change	read	scale	to	analog	out	scale	
Setpoint	=	map(analogRead(pot),	0,	1024,	0,	255);	//get	our	setpoint	from	our	pot
Serial.begin(9600);	//Start	a	serial	session	
myPID.SetMode(AUTOMATIC);	//Turn	on	the	PID	loop
myPID.SetSampleTime(sampleRate);	//Sets	the	sample	rate
Serial.println("Begin");	//	Hello	World!
lastMessage	=	millis();	//	timestamp
}

void loop() {
  // put your main code here, to run repeatedly:
Setpoint	=	map(analogRead(pot),	0,	1024,	0,	255);	//Read	our	setpoint	
lightLevel	=	analogRead(photores);//Get	the	light	level
Input	=	map(lightLevel,	0,	900,	0,	255);	//Map	it	to	the	right	scale
myPID.Compute();//Run	the	PID	loop
analogWrite(led,	Output);	//Write	out	the	output	from	the	PID	loop	to	our	LED	pin
now	=	millis();//Keep	track	of	time
if(now	- lastMessage	>	serialPing)	{	//If	it	has	been	long	enough	give	us	
// some	info	on	serial
//	this	should	execute	less	frequently	
//	send	a	message	back	to	the	mother	ship	
Serial.print("Setpoint	=	");	
Serial.print(Setpoint);	
Serial.print("	Input	=	");	
Serial.print(Input);	
Serial.print("	Output	=	");	
Serial.print(Output);	
Serial.print("\n");	
if	(Serial.available()	>	0)	{	//If	we	sent	the	program	a	command	deal	with	it	
for	(int x=0;x<4;x++)	{	
switch	(x)	{	
case	0:
Kp	=	Serial.parseFloat();	
break;	
case	1:
Ki	=	Serial.parseFloat();	
break;	
case	2:
Kd	=	Serial.parseFloat();	
break;	
case	3:
for	(int	y	=	Serial.available();	y	==	0;	y--)	{	
Serial.read();	//Clear	out	any	residual	junk	
}	
break;	
}	
}
Serial.print("	Kp,Ki,Kd	=	");	
Serial.print(Kp);	
Serial.print(",");	
Serial.print(Ki);
Serial.print(",");
Serial.println(Kd);	//Let	us	know	what	we	just	received	
myPID.SetTunings(Kp,	Ki,	Kd);	//Set	the	PID	gain	constants	and	start	running	
}	
lastMessage	=	now;	
 //update	the	time	stamp.
}
}