#define LDR_UP A1
#define LDR_DOWN A2
#define VOLTAGE_SENSOR A3  // Simulated by potentiometer
#define CURRENT_SENSOR A4  // Simulated by potentiometer

const int forward = 8;
const int backward = 9;
const int speedPin = 10;

// ** Variables for Voc and Isc **
float Voc = 0;  // Open Circuit Voltage
float Isc = 0;  // Short Circuit Current
bool measured = false;  // Flag to check if Voc/Isc is measured

void setup() {
  Serial.begin(9600);
  pinMode(forward, OUTPUT);
  pinMode(backward, OUTPUT);
  pinMode(speedPin, OUTPUT);
}

void loop() {
  // **Step 1: Measure Voc & Isc Only Once**
  if (!measured) {
    measureVocIsc();
    measured = true;  // Ensure it's only measured once
  }

  // **Step 2: Read Sensor Data**
  int lightUp = analogRead(LDR_UP);
  int lightDown = analogRead(LDR_DOWN);
  int luxDifference = lightUp - lightDown;

  float voltage = analogRead(VOLTAGE_SENSOR) * (25.0 / 1023.0);
  float current_raw = analogRead(CURRENT_SENSOR) * (5.0 / 1023.0);

  // **Step 3: Limit the PV Curve Based on Voc & Isc**
  float current = Isc * (1 - exp(-voltage / Voc));  // PV Curve Limiting
  float power = voltage * current;  // Corrected PV Power

  // **Step 4: Solar Tracker Movement**
  int motorSpeed = map(abs(luxDifference), 0, 200, 150, 255);

  if (lightUp < 10 && lightDown < 10) {  
    Serial.println("Returning to Start Position");
    digitalWrite(forward, LOW);
    digitalWrite(backward, HIGH);
    analogWrite(speedPin, 100);
  }  
  else if (luxDifference > 30) {  
    Serial.println("Moving Forward");
    digitalWrite(forward, HIGH);
    digitalWrite(backward, LOW);
    analogWrite(speedPin, motorSpeed);
  }  
  else if (luxDifference < 5) {  
    Serial.println("Waiting (Cloud detected)");
    digitalWrite(forward, LOW);
    digitalWrite(backward, LOW);
    delay(5000);
  }  
  else {  
    Serial.println("Stopping");
    digitalWrite(forward, LOW);
    digitalWrite(backward, LOW);
  }  

  // **Step 5: Display PV Data**
  Serial.print("Voc: "); Serial.print(Voc); Serial.print("\t");
  Serial.print("Isc: "); Serial.print(Isc); Serial.print("\t");
  Serial.print("Voltage: "); Serial.print(voltage); Serial.print("\t");
  Serial.print("Current: "); Serial.print(current); Serial.print("\t");
  Serial.print("Power: "); Serial.print(power); Serial.print("\t");
  Serial.print("Light Up: "); Serial.print(lightUp); Serial.print("\t");
  Serial.print("Light Down: "); Serial.print(lightDown); Serial.print("\t");
  Serial.print("Motor Speed: "); Serial.println(motorSpeed);

  delay(1000);
}

// **Function to Measure Voc and Isc**
void measureVocIsc() {
  // Measure Voc (Max Voltage when Current = 0)
  float sumVoc = 0;
  for (int i = 0; i < 10; i++) {  // Take multiple readings for accuracy
    sumVoc += analogRead(VOLTAGE_SENSOR) * (25.0 / 1023.0);
    delay(100);
  }
  Voc = sumVoc / 10;  // Average Voc

  // Measure Isc (Max Current when Voltage = 0)
  float sumIsc = 0;
  for (int i = 0; i < 10; i++) {
    sumIsc += analogRead(CURRENT_SENSOR) * (5.0 / 1023.0);
    delay(100);
  }
  Isc = sumIsc / 10;  // Average Isc

  Serial.print("Measured Voc: "); Serial.println(Voc);
  Serial.print("Measured Isc: "); Serial.println(Isc);
}