// Intelligent lighting system

#define LDR_PIN_AO  A0
#define LED_PIN     10
#define PIR_OUT_PIN 13
// Arduino ADC parameters
const float VREF = 5.0;
const float ADC_resolution = 10;

void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(PIR_OUT_PIN, INPUT);
  Serial.begin(115200);
}

float get_ldr_voltage() {
  int analog_value = analogRead(LDR_PIN_AO); // Reads the analog value from pin
  // Voltage conversion formula
  float voltage = (analog_value / pow(2,ADC_resolution)) * VREF;
  return voltage;
}

bool motion_detection() {
  // a logic HIGH in PIR OUT corresponds to motion
  if (digitalRead(PIR_OUT_PIN) == HIGH) {
    return true;
  }
  // a logic LOW in PIR OUT corresponds to no motion
  else {
    return false;
  }
}

void loop() {
  float voltage_val = get_ldr_voltage();
  Serial.print("LDR voltage : ");
  Serial.println(voltage_val);
  bool poor_lighting;
  // Voltage value for office lighting is 1.37V and for Stairway lighting is 2.5V
  // Hence choosing a value of 2V between this range.
  // Any value greater than 2V can be assumed to be poor lighting.
  if (voltage_val > 2.0) {
    poor_lighting = true;
  } else {
    poor_lighting = false;
  }

  bool motion = motion_detection();

  // Turn ON LED if room if poorly lit and motion is detected
  if (motion == true && poor_lighting == true) {
    digitalWrite(LED_PIN, HIGH);
  } else {
    digitalWrite(LED_PIN, LOW);
  }

  delay(100);
}