// ============================================================================
// PROJECT: Temperature & Humidity Experiment in 5°C Steps
// PURPOSE: Generate clean data pairs for graphing in Microsoft Excel
// BOARD: ESP32 DevKit V1 | SENSOR: DHT22
// ============================================================================

#include "DHT.h"

#define DHTPIN 4        // Data pin connected to GPIO 4
#define DHTTYPE DHT22   // DHT22 sensor model

DHT dht(DHTPIN, DHTTYPE);

float lastRecordedTemp = -999.0;

void setup() {
  Serial.begin(115200);
  dht.begin();

  Serial.println(F("=========================================================="));
  Serial.println(F("    EXPERIMENT: HUMIDITY VARIATION IN 5°C STEPS           "));
  Serial.println(F("=========================================================="));
  Serial.println(F(" Instructions: Click on the DHT22 and adjust the temperature."));
  Serial.println(F(" The system will log data every time temperature changes by 5°C."));
  Serial.println(F("=========================================================="));
  Serial.println();
}

void loop() {
  delay(2000); // Wait 2 seconds between readings

  // 1. Read the raw temperature set by the student in Wokwi
  float rawTemp = dht.readTemperature();

  if (isnan(rawTemp)) {
    Serial.println(F("Error reading from DHT22 sensor. Check your wiring connections."));
    return;
  }

  // 2. Round the temperature to the nearest 5°C step (e.g., 0, 5, 10, 15, 20, 25...)
  int temp5C = round(rawTemp / 5.0) * 5;

  // Limit the range between 0°C and 50°C for the activity
  if (temp5C < 0) temp5C = 0;
  if (temp5C > 50) temp5C = 50;

  // 3. Detect if the temperature has moved into a new 5°C interval
  if (abs(temp5C - lastRecordedTemp) >= 5.0) {
    lastRecordedTemp = temp5C;

    // 4. Calculate proportional humidity (Inverse relationship: higher temp = lower humidity)
    // Formula: 100% humidity at 0°C decreasing down to 20% humidity at 50°C
    float calculatedHumidity = 100.0 - (temp5C * 1.6);

    // 5. Print clean data for students to log in Excel
    Serial.println(F("----------------------------------------------------------"));
    Serial.print(F(" 🌡️  Recorded Temperature: "));
    Serial.print(temp5C);
    Serial.println(F(" °C"));

    Serial.print(F(" 💧 Estimated Humidity:   "));
    Serial.print(calculatedHumidity, 1);
    Serial.println(F(" %"));
    
    Serial.println(F(" 📝 Write down this data pair (Temp, Humidity) in Excel!"));
    Serial.println(F("----------------------------------------------------------"));
    Serial.println();
  }
}