#include <PID_v1.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Wire.h>

// OLED Display Settings
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Pin Definitions
const int ntcPin = A0;          // NTC thermistor analog pin
const int heaterPin = 9;        // PWM pin for heater control
const int buttonUpPin = 2;      // Button to increase setpoint
const int buttonDownPin = 3;    // Button to decrease setpoint

// PID Variables
double setpoint = 30.0;         // Initial setpoint temperature
double input, output;
double Kp = 2.0, Ki = 0.5, Kd = 1.0; // PID tuning parameters
PID myPID(&input, &output, &setpoint, Kp, Ki, Kd, DIRECT);

// NTC Thermistor Variables
const double beta = 3950.0;     // Beta value for the NTC thermistor
const double nominalResistance = 10000.0; // Resistance at 25°C
const double nominalTemp = 25.0; // Temperature for nominal resistance
const double seriesResistor = 10000.0; // Series resistor value

// Button Variables
bool lastButtonUpState = HIGH;
bool lastButtonDownState = HIGH;

void setup() {
  // Initialize Serial Monitor
  Serial.begin(9600);

  // Initialize OLED Display


  // Initialize OLED
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("OLED failed"));
    while(1);

  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("PID Temp Control");
  display.display();
  delay(2000);

  // Initialize PID
  myPID.SetMode(AUTOMATIC);
  myPID.SetOutputLimits(0, 255); // PWM range

  // Initialize Buttons
  pinMode(buttonUpPin, INPUT_PULLUP);
  pinMode(buttonDownPin, INPUT_PULLUP);

  // Initialize Heater Pin
  pinMode(heaterPin, OUTPUT);
}

void loop() {
  // Read Temperature
  input = readTemperature();

  // Compute PID
  myPID.Compute();

  // Control Heater
  analogWrite(heaterPin, output);

  // Adjust Setpoint with Buttons
  adjustSetpoint();

  // Update OLED Display
  updateDisplay();

  // Small delay for stability
  delay(100);
}

double readTemperature() {
  int analogValue = analogRead(ntcPin);
  double resistance = seriesResistor / (1023.0 / analogValue - 1.0);
  double temperature = 1.0 / (1.0 / (nominalTemp + 273.15) + log(resistance / nominalResistance) / beta) - 273.15;
  return temperature;
}

void adjustSetpoint() {
  bool buttonUpState = digitalRead(buttonUpPin);
  bool buttonDownState = digitalRead(buttonDownPin);

  if (buttonUpState == LOW && lastButtonUpState == HIGH) {
    setpoint += 1.0; // Increase setpoint by 1°C
  }
  if (buttonDownState == LOW && lastButtonDownState == HIGH) {
    setpoint -= 1.0; // Decrease setpoint by 1°C
  }

  lastButtonUpState = buttonUpState;
  lastButtonDownState = buttonDownState;
}

void updateDisplay() {
  display.clearDisplay();
  display.setCursor(0, 0);
  display.print("Temp: ");
  display.print(input);
  display.println(" C");
  display.setCursor(0, 20);
  display.print("Set: ");
  display.print(setpoint);
  display.println(" C");
  display.setCursor(0, 40);
  display.print("Output: ");
  display.print(output);
  display.display();
}