#include <PID_v1.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 storing values

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

// placehodler for current timestamp

unsigned long lastMessage = 0; //This keeps track of when our loop last spoke to serial

// last message timestamp.

void setup(){

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(){

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 its 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.

}

}