#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int mq2 = A0;
const int mq5 = A2;

void setup() {
  lcd.begin(16, 2);
  lcd.backlight();
  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("    SENSORES    ");
  lcd.setCursor(0, 1);
  lcd.print(" SMART DE GASES");
  delay(4000);
  lcd.clear();

  pinMode(mq5, INPUT);
  pinMode(mq2, INPUT);

  Serial.begin(9600);
}

void loop() {
  double mq5_value = analogToPPM(analogRead(mq5), 21.91, -0.6527, 1.30);
  double mq2_value = analogToPPM(analogRead(mq2), 21.91, -0.6527, 1.30);

  displayValue("LNG", mq5_value);
  delay(3000);
  
  displayValue("SMOKE", mq2_value);
  delay(3000);
}

void displayValue(const char* gasName, double value) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(gasName);
  lcd.setCursor(0, 3);
  lcd.print(value);
  lcd.setCursor(7, 7);
  lcd.print("PPM");
}

double analogToPPM(int sensorValue, float R0, float m, float b) {
  float sensor_volt = sensorValue * (5.0 / 1023.0);
  float RS_gas = ((5.0 * 10.0) / sensor_volt) - 10.0;
  float ratio = RS_gas / R0;
  double ppm_log = (log10(ratio) - b) / m;
  return ppm_log;
}