Arduino Nano

#include <ArduinoJson.h>

#include <LiquidCrystal.h>

#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <DHT_U.h>

#define PIR_PIN 4
#define DHTPIN 1
#define DHTTYPE DHT22
DHT_Unified dht(DHTPIN, DHTTYPE);

LiquidCrystal lcd(8, 9, 7, 6, 5, 4);

enum msg {
  SENSOR_INFO,
  DOOR,
};

void setup() {
  pinMode(DHTPIN, INPUT);
  pinMode(PIR_PIN, INPUT);

  dht.begin();
  lcd.begin(16, 2);
  Serial.begin(9600);

  attachInterrupt(digitalPinToInterrupt(PIR_PIN), openDoorISR, RISING);
  attachInterrupt(digitalPinToInterrupt(PIR_PIN), closeDoorISR, FALLING);
}

void loop() {
  handleLcd();
  delay(1000);
}

void serialEvent()
{
  StaticJsonDocument<15> doc;
  deserializeJson(doc, Serial);
  int act = doc["action"];
  if (act == SENSOR_INFO)
  {
    sendSensorInfo();
  }
}

void sendSensorInfo()
{
  StaticJsonDocument<40> doc;
  doc["action"] = SENSOR_INFO;
  doc["temp"] = getTemp();
  doc["hmd"] = getHumidity();
  serializeJson(doc, Serial);
  Serial.println();
}

void handleDoor(bool state) {
  StaticJsonDocument<20> doc;
  doc["action"] = DOOR;
  doc["state"] = state;
  serializeJson(doc, Serial);
  Serial.println();
}

void handleLcd() {
  float temperature = getTemp();
  int humidity = getHumidity();
  printToLcd(temperature, humidity);
}

float getTemp()
{
  sensors_event_t event;
  dht.temperature().getEvent(&event);
  if (isnan(event.temperature)) {
    return 0;
  }
  else {
    return event.temperature;
  }
}

int getHumidity()
{
  sensors_event_t event;
  dht.humidity().getEvent(&event);
  if (isnan(event.relative_humidity)) {
    return 0;
  }
  else {
    return event.relative_humidity;
  }
}

void printToLcd(float temp, int hmd) {
  lcd.clear();
  String tempData = "Temp: " + String(temp);
  lcd.print(tempData);
  lcd.setCursor(0, 1);
  String tempHmd = "Humd: " + String(hmd) + "%";
  lcd.print(tempHmd);
}

void openDoorISR() {
  handleDoor(true);
}

void closeDoorISR() {
  handleDoor(false);
}