/*
 * ESP32 Photoresistor Light Sensor with LED Indicator
 * 
 * This program reads light intensity using a photoresistor (LDR - Light Dependent Resistor)
 * and controls an LED based on the ambient light level.
 * 
 * Hardware Setup for Wokwi:
 * - ESP32 board
 * - Photoresistor (LDR) connected to GPIO 25 (ADC pin)
 * - LED connected to GPIO 12 with current limiting resistor
 * 
 * The photoresistor forms a voltage divider circuit with a fixed resistor,
 * and the ESP32's ADC reads the voltage to calculate light intensity in Lux.
 */

// Constants for LDR calculations
const float GAMMA = 0.7;        // Gamma correction factor for the specific LDR type
const float RL10 = 50;          // LDR resistance at 10 Lux (from datasheet)
const int LDR_PIN = 25;         // Analog pin connected to photoresistor
const int LED_PIN = 12;         // Digital pin connected to LED
const float THRESHOLD_LUX = 50; // Light threshold to determine bright/dark

// Variables for sensor readings
float lux = 0;
int analogValue = 0;
float voltage = 0;
float resistance = 0;

void setup() {
  // Initialize serial communication at 115200 baud rate
  Serial.begin(115200);
  
  // Configure LED pin as output
  pinMode(LED_PIN, OUTPUT);
  
  // Configure ADC resolution (ESP32 default is 12-bit = 4096 levels)
  analogReadResolution(12);
  
  // Initial message
  Serial.println("=== ESP32 Light Sensor Started ===");
  Serial.println("Monitoring ambient light level...\n");
  
  // Turn off LED initially
  digitalWrite(LED_PIN, LOW);
}

void loop() {
  // Read analog value from photoresistor (0-4095 for 12-bit ADC)
  analogValue = analogRead(LDR_PIN);
  
  // Convert ADC reading to voltage
  voltage = analogValue * 5 / 4095.0;
  
  // Calculate photoresistor resistance using voltage divider formula
  // Assuming a 2kΩ pull-down resistor in the voltage divider
  if (voltage > 0.1) { // Avoid division by very small numbers
    resistance = 2000 * voltage / (1 - voltage / 5);
  } else {
    resistance = 999999; // Very high resistance (very dark)
  }
  
  // Convert resistance to Lux using the photoresistor's characteristic curve
  // This formula is specific to the LDR type and may need calibration
  if (resistance > 0) {
    lux = pow((RL10 * 1000 * pow(10, GAMMA)) / resistance, (1.0 / GAMMA));
  } else {
    lux = 0;
  }
  
  // Limit unrealistic values
  if (lux > 10000) lux = 10000;
  if (lux < 0) lux = 0;
  
  // Display readings on serial monitor
  Serial.print("ADC Reading: ");
  Serial.print(analogValue);
  Serial.print(" | Voltage: ");
  Serial.print(voltage, 2);
  Serial.print("V | Resistance: ");
  Serial.print(resistance, 0);
  Serial.print("Ω | Lux: ");
  Serial.print(lux, 1);
  
  // Determine light condition and control LED
  if (lux >= THRESHOLD_LUX) {
    Serial.print(" | Status: Terang (Bright)");
    digitalWrite(LED_PIN, LOW);  // Turn OFF LED when it's bright
  } else {
    Serial.print(" | Status: Gelap (Dark)");
    digitalWrite(LED_PIN, HIGH); // Turn ON LED when it's dark
  }
  
  Serial.println(); // New line
  
  // Wait 500ms before next reading (reduced frequency for better readability)
  delay(500);
}