Generate A Clean High-resolution Technical Engin

#include <HardwareSerial.h>
#include <Arduino.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <DHT.h>

// Forward declarations
String fit16(String text);
void showStatus(const String &line1, const String &line2);
bool readAcknowledgePress();

constexpr uint8_t LCD_SDA_PIN = 4;   // NodeMCU D2
constexpr uint8_t LCD_SCL_PIN = 5;   // NodeMCU D1
constexpr uint8_t DHT_PIN = 0;       // NodeMCU D3
constexpr uint8_t BUZZER_PIN = 14;   // NodeMCU D5
constexpr uint8_t BT_RX_PIN = 12;    // NodeMCU D6, receives HC-05 TX
constexpr uint8_t BT_TX_PIN = 13;    // NodeMCU D7, sends HC-05 RX
constexpr uint8_t MQ2_PIN = A0;
constexpr uint8_t BUTTON_PIN = 16;   // NodeMCU D0

constexpr int GAS_ALARM_LEVEL = 650;
constexpr unsigned long SAMPLE_INTERVAL_MS = 2000;
constexpr unsigned long DEBOUNCE_MS = 40;

LiquidCrystal_I2C lcd(0x27, 16, 2);
DHT dht(DHT_PIN, DHT11);
HardwareSerial bluetooth(2);

bool alarmAcknowledged = false;
bool previousButtonReading = HIGH;
bool stableButtonState = HIGH;
unsigned long lastButtonChangeMs = 0;
unsigned long lastSampleMs = 0;
String lastLine1;
String lastLine2;

String fit16(String text) {
  if (text.length() > 16) return text.substring(0, 16);
  while (text.length() < 16) text += ' ';
  return text;
}

void showStatus(const String &line1, const String &line2) {
  if (line1 != lastLine1) {
    lcd.setCursor(0, 0);
    lcd.print(fit16(line1));
    lastLine1 = line1;
  }
  if (line2 != lastLine2) {
    lcd.setCursor(0, 1);
    lcd.print(fit16(line2));
    lastLine2 = line2;
  }
}

bool readAcknowledgePress() {
  bool reading = digitalRead(BUTTON_PIN);
  if (reading != previousButtonReading) lastButtonChangeMs = millis();

  if ((millis() - lastButtonChangeMs) > DEBOUNCE_MS && reading != stableButtonState) {
    stableButtonState = reading;
    if (stableButtonState == LOW) {
      previousButtonReading = reading;
      return true;
    }
  }
  previousButtonReading = reading;
  return false;
}

void setup() {
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  digitalWrite(BUZZER_PIN, LOW);

  Wire.begin(LCD_SDA_PIN, LCD_SCL_PIN);
  lcd.init();
  lcd.backlight();
  dht.begin();
  bluetooth.begin(9600, SERIAL_8N1, BT_RX_PIN, BT_TX_PIN);

  showStatus("Safety Vest", "Starting sensor");
  delay(1200);
}

void loop() {
  if (readAcknowledgePress()) {
    alarmAcknowledged = true;
  }

  if (millis() - lastSampleMs < SAMPLE_INTERVAL_MS) return;
  lastSampleMs = millis();

  float humidity = dht.readHumidity();
  float temperatureC = dht.readTemperature();
  int gasRaw = analogRead(MQ2_PIN);
  bool gasAlarm = gasRaw >= GAS_ALARM_LEVEL;
  bool dhtValid = !isnan(humidity) && !isnan(temperatureC);

  if (!gasAlarm) alarmAcknowledged = false;
  bool soundAlarm = gasAlarm && !alarmAcknowledged;
  digitalWrite(BUZZER_PIN, soundAlarm ? HIGH : LOW);

  String line1;
  if (dhtValid) {
    line1 = "T:" + String(temperatureC, 1) + "C H:" + String((int)humidity) + "%";
  } else {
    line1 = "DHT11 check";
  }

  String line2 = "Gas:" + String(gasRaw);
  if (gasAlarm) line2 += alarmAcknowledged ? " ACK" : " ALERT";
  showStatus(line1, line2);

  bluetooth.print("TEMP=");
  if (dhtValid) bluetooth.print(temperatureC, 1); else bluetooth.print("NA");
  bluetooth.print(",HUM=");
  if (dhtValid) bluetooth.print(humidity, 0); else bluetooth.print("NA");
  bluetooth.print(",MQ2=");
  bluetooth.print(gasRaw);
  bluetooth.print(",ALARM=");
  bluetooth.println(gasAlarm ? "1" : "0");
}