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

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

#define OLED_RESET    -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define MQ137_PIN 34    // Analog pin for MQ137 sensor
#define BUZZER_PIN 25   // Digital pin for buzzer
#define PPM_THRESHOLD 100 // PPM threshold for triggering the buzzer

void setup() {
  // Initialize serial communication at 115200 baud rate
  Serial.begin(115200);

  // Initialize the SSD1306 display with I2C address 0x3C
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }

  // Clear the buffer
  display.clearDisplay();
  
  // Display static text
  display.setTextSize(1);      
  display.setTextColor(SSD1306_WHITE); 
  display.setCursor(0, 0);     
  display.println(F("MQ137 PPM and Concentration"));
  display.display();

  // Initialize the buzzer pin
  pinMode(BUZZER_PIN, OUTPUT);
  digitalWrite(BUZZER_PIN, LOW); // Ensure the buzzer is off initially
}

void loop() {
  // Read from MQ137 sensor
  int adcValue = analogRead(MQ137_PIN); 
  float voltage = adcValue * (3.3 / 4095.0); // Convert to voltage (ESP32 ADC range is 0-4095)

  // Convert voltage to PPM (this is a simplified example, proper calibration is required)
  float ppm = (voltage - 0.1) * 100;
  
  // Calculate concentration from PPM (example calculation, needs calibration)
  float concentration = ppm * 0.1; // Example conversion factor

  // Display values on Serial Monitor
  Serial.print("ADC Value: "); Serial.print(adcValue);
  Serial.print(", Voltage: "); Serial.print(voltage);
  Serial.print(", PPM: "); Serial.print(ppm);
  Serial.print(", Concentration: "); Serial.println(concentration);
  
  // Display values on OLED
  display.clearDisplay();
  display.setCursor(0, 10); // Start a bit lower to avoid overlap
  display.print("PPM: ");
  display.print(ppm);
  display.setCursor(0, 30); // Move cursor down for concentration
  display.print("Concentration: ");
  display.print(concentration);
  display.display();
  
  // Check if PPM exceeds the threshold
  if(ppm > PPM_THRESHOLD) {
    digitalWrite(BUZZER_PIN, HIGH); // Turn on the buzzer
  } else {
    digitalWrite(BUZZER_PIN, LOW); // Turn off the buzzer
  }
  
  delay(1000); // Update every second
}