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	- Project: "H₂S Sensor"
	- Source Code NOT compiled for: Arduino Nano ESP32
	- Source Code created on: 2024-06-09 07:51:42

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/****** SYSTEM REQUIREMENTS *****/
/****** SYSTEM REQUIREMENT 1 *****/
	/* Design an H2S detection system with the MQ136 */
	/* sensor. The system should capture digital and */
	/* analog outputs, send data to a cloud server for */
	/* remote monitoring, and use an LCD and buzzer to */
	/* alert users of high H2S concentrations. */
/****** END SYSTEM REQUIREMENTS *****/

/****** DEFINITION OF LIBRARIES *****/
#include <Wire.h>
#include <MQUnifiedsensor.h>  // https://github.com/miguel5612/MQSensorsLib
#include <LCDIC2.h>  // https://github.com/offcircuit/LCDIC2
#include <WiFi.h>  // For WiFi connectivity to send data to cloud server
#include <HTTPClient.h>  // For HTTP requests to send data to cloud server

/****** FUNCTION PROTOTYPES *****/
void setup(void);
void loop(void);
void sendDataToCloud(float ppm);

/***** DEFINITION OF DIGITAL INPUT PINS *****/
const uint8_t myHydro_MQ136_DOUT_PIN_D2 = 2;
const uint8_t buzzerPin = 3;  // Pin for buzzer

/***** DEFINITION OF ANALOG INPUT PINS *****/
const uint8_t myHydro_MQ136_AOUT_PIN_A0 = A0;

/***** DEFINITION OF I2C PINS *****/
const uint8_t LCD1602_Display_LCD1602I2C_I2C_PIN_SDA_A4 = A4;
const uint8_t LCD1602_Display_LCD1602I2C_I2C_PIN_SCL_A5 = A5;
const uint8_t LCD1602_Display_LCD1602I2C_I2C_SLAVE_ADDRESS = 0x27; // 39 in decimal

/****** DEFINITION OF LIBRARIES CLASS INSTANCES*****/
// Definitions for MQ136 sensor
#define placa "Arduino UNO"
#define Voltage_Resolution 5
#define type "MQ-136"  // MQ136
#define ADC_Bit_Resolution 10  // For Arduino UNO/MEGA/NANO
#define RatioMQ136CleanAir 3.6  // RS / R0 = 3.6 ppm

// Declare Sensor
MQUnifiedsensor MQ136(placa, Voltage_Resolution, ADC_Bit_Resolution, myHydro_MQ136_AOUT_PIN_A0, type);

// Declare LCD
LCDIC2 lcd(LCD1602_Display_LCD1602I2C_I2C_SLAVE_ADDRESS, 16, 2);

// WiFi credentials
const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";

// Cloud server URL
const char* serverName = "http://yourserver.com/api/data";

void setup(void)
{
  // Initialize the serial port communication
  Serial.begin(9600);

  // Initialize the LCD
  if (lcd.begin()) {
    lcd.print("Initializing...");
  }

  // Initialize WiFi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
    lcd.setCursor(0, 1);
    lcd.print("Connecting WiFi...");
  }
  Serial.println("Connected to WiFi");
  lcd.clear();
  lcd.print("WiFi Connected");

  // Set math model to calculate the PPM concentration and the value of constants
  MQ136.setRegressionMethod(1);  // _PPM = a*ratio^b
  MQ136.setA(36.737); 
  MQ136.setB(-3.536);  // Configure the equation to calculate H2S Concentration

  // Initialize the sensor
  MQ136.init(); 

  // Calibrate the sensor
  Serial.print("Calibrating please wait.");
  lcd.setCursor(0, 1);
  lcd.print("Calibrating...");
  float calcR0 = 0;
  for(int i = 1; i <= 10; i++) {
    MQ136.update();  // Update data, the Arduino will read the voltage from the analog pin
    calcR0 += MQ136.calibrate(RatioMQ136CleanAir);
    Serial.print(".");
  }
  MQ136.setR0(calcR0 / 10);
  Serial.println("  done!");
  lcd.clear();
  lcd.print("Calibration done!");

  // Check for connection issues
  if(isinf(calcR0)) {
    Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply");
    lcd.clear();
    lcd.print("Conn issue: R0 inf");
    while(1);
  }
  if(calcR0 == 0) {
    Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply");
    lcd.clear();
    lcd.print("Conn issue: R0 0");
    while(1);
  }

  // Enable serial debugging
  MQ136.serialDebug(true);

  // Initialize pins
  pinMode(myHydro_MQ136_DOUT_PIN_D2, INPUT_PULLUP);
  pinMode(myHydro_MQ136_AOUT_PIN_A0, INPUT);
  pinMode(buzzerPin, OUTPUT);
}

void loop(void)
{
  MQ136.update();  // Update data, the Arduino will read the voltage from the analog pin
  MQ136.readSensor();  // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
  MQ136.serialDebug();  // Will print the table on the serial port

  // Display PPM concentration on LCD
  lcd.setCursor(0, 0);
  lcd.print("H2S PPM: ");
  lcd.print(MQ136.getPPM());

  // Send data to cloud server
  sendDataToCloud(MQ136.getPPM());

  // Check if H2S concentration is above threshold and activate buzzer
  if (MQ136.getPPM() > 10) {  // Threshold value for H2S concentration
    digitalWrite(buzzerPin, HIGH);  // Turn on buzzer
  } else {
    digitalWrite(buzzerPin, LOW);  // Turn off buzzer
  }

  delay(500);  // Sampling frequency
}

void sendDataToCloud(float ppm) {
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    http.begin(serverName);
    http.addHeader("Content-Type", "application/x-www-form-urlencoded");

    String httpRequestData = "ppm=" + String(ppm);
    int httpResponseCode = http.POST(httpRequestData);

    if (httpResponseCode > 0) {
      String response = http.getString();
      Serial.println(httpResponseCode);
      Serial.println(response);
    } else {
      Serial.print("Error on sending POST: ");
      Serial.println(httpResponseCode);
    }
    http.end();
  } else {
    Serial.println("Error in WiFi connection");
  }
}