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

#define SPO2_ADDRESS 0x11     // I2C address of the custom SPO2 sensor
#define MQ2_PIN 34            // Analog pin for MQ2 sensor
#define CO2_THRESHOLD 2500    // Updated CO2 threshold for apnea detection

// LCD I2C address (0x27 or 0x3F depending on your module)
LiquidCrystal_I2C lcd(0x27, 16, 2); 

void setup() {
  Serial.begin(115200);
  Serial.println("Starting SPO2 + MQ2 Monitor");

  // Initialize I2C for SPO2 and LCD
  Wire.begin(21, 22); // SDA = GPIO 21, SCL = GPIO 22

  // Initialize LCD
  lcd.begin(16, 2);
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Initializing...");
  delay(2000);
}

void loop() {
  byte spo2 = 0;

  // Request SPO2 value from custom chip
  Wire.requestFrom(SPO2_ADDRESS, 1);
  if (Wire.available()) {
    spo2 = Wire.read();
  }

  // Read CO2 from MQ2 sensor
  int co2Value = analogRead(MQ2_PIN);

  // Print to Serial Monitor
  Serial.print("SpO2: ");
  Serial.print(spo2);
  Serial.print("% | CO2: ");
  Serial.println(co2Value);

  // Update LCD
  lcd.clear();

  // Line 1: SpO2 display
  lcd.setCursor(0, 0);
  lcd.print("SpO2: ");
  lcd.print(spo2);
  lcd.print("%");

  // Line 2: CO2 and Apnea
  lcd.setCursor(0, 1);
  lcd.print("CO2: ");
  lcd.print(co2Value);
  
  if (co2Value > CO2_THRESHOLD) {
    lcd.setCursor(10, 1);  // Adjust to fit within 16 chars
    lcd.print("Apnea");
  } else {
    lcd.setCursor(10, 1);
    lcd.print("  OK ");
  }

  delay(1000);
}