Arduino RFID System Based on RS485

#include <SPI.h>
#include <MFRC522.h>
#include <LiquidCrystal.h>
#include <Wire.h>
#include "RTClib.h"
#include <SoftwareSerial.h>
#include <EEPROM.h>

#define rs485_RX A0
#define rs485_TX A1
#define rs485_DE A2
#define rs485_RE A3
SoftwareSerial rs485(rs485_RX, rs485_TX); // RX, TX


//RFID
#define SS_PIN 10
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN);
String cards[10] = {"", "", "", "", "", "", "", "", "", ""};
String check;
String check_card;
String check_time;
String point = "Point A"; //Point B, Point C
String PORT = "01"; //FROM 01,02,03 TO FE - Total of 254 Slave stations
String MASTER_PORT = "FF";

//Time
RTC_DS1307 rtc;
String currentTime, DD, MM, YYYY, hh, mm;

//LCD
LiquidCrystal lcd(2, 3, 4, 5, 6, 7);

//Buzzer
#define buzzer 8

//Serial Communication
char incomingByte;
String command;
boolean messageCompleted = false;
boolean newMessage = false;

void setup() {
  pinMode(rs485_RE, OUTPUT);
  pinMode(rs485_DE, OUTPUT);
  digitalWrite(rs485_RE, LOW);
  digitalWrite(rs485_DE, LOW);
  Serial.begin(9600);   // Initiate a serial communication
  rs485.begin(19200);
  //RFID
  SPI.begin();      // Initiate  SPI bus
  mfrc522.PCD_Init();   // Initiate MFRC522

  //RTC
  if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }
  if (! rtc.isrunning()) {
    Serial.println("RTC is NOT running!");
  }

  //LCD
  lcd.begin(16, 2);

  //Buzzer
  pinMode(buzzer, OUTPUT);
  //Read last check from EEPROM memory (card id and timestamp)
  delay(10);
  check_card = readFromMemory(0, 8);
  delay(10);
  check_time = readFromMemory(10, 16);
  delay(10);
  //Read Card id list from memory
  for (int i = 0; i < 10; i++) {
    cards[i] = readFromMemory(30 + (i * 10), 8);
    //storeInMemory(30 + (i*10), "xxxxxxxx");
    delay(10);
    Serial.println(cards[i]);
  }
  Serial.println("System is up and running");
}


void setTime(int YYYY, int MM, int DD, int hh, int mm) {
  rtc.adjust(DateTime(YYYY, MM, DD, hh, mm, 0));
}

void readTime() {
  //DAY
  DateTime now = rtc.now();
  if (now.day() <= 9) {
    DD = "0" + String(now.day());
  }
  else {
    DD = String(now.day());
  }

  //MONTH
  if (now.month() <= 9) {
    MM = "0" + String(now.month());
  }
  else {
    MM = String(now.month());
  }

  //HOUR
  if (now.hour() <= 9) {
    hh = "0" + String(now.hour());
  }
  else {
    hh = String(now.hour());
  }

  //MINUTE
  if (now.minute() <= 9) {
    mm = "0" + String(now.minute());
  }
  else {
    mm = String(now.minute());
  }

  //YEAR
  if (now.year()) {
    YYYY = String(now.year());
  }
  currentTime = DD + "/" + MM + "/" + YYYY + " " + hh + ":" + mm;
}

void checkCard() {
  if ( ! mfrc522.PICC_IsNewCardPresent())
  {
    check = "";
    return;
  }
  // Select one of the cards
  if ( ! mfrc522.PICC_ReadCardSerial())
  {
    check = "";
    return;
  }
  //Show UID on serial monitor
  String card = "";
  for (byte i = 0; i < mfrc522.uid.size; i++)
  {
    card.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
    card.concat(String(mfrc522.uid.uidByte[i], HEX));
  }
  card.toUpperCase();
  card = card.substring(1);
  card.replace(" ", "");
  for (int i = 0; i < 10; i++) {
    if (card == cards[i]) {
      check = "VALID: " + String(card);
      check_card = String(card);
      check_time = currentTime;
      storeInMemory(0, check_card); //Start store card id from memory addr 0
      storeInMemory(10, check_time); //Start store time stamp from memory addr 10
      return;
    }
    else {
      check = "Card Not found...";
    }
  }
}

void printLCD(String line1, String line2) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(line1);
  lcd.setCursor(0, 1);
  lcd.print(line2);
}

void buzzerTone() {
  tone(buzzer, 1000); // Send 1KHz sound signal...
  delay(1000);        // ...for 1 sec
  noTone(buzzer);     // Stop sound...
}

void storeInMemory(char addr, String data) {
  int _size = data.length();
  int i;
  for (i = 0; i < _size; i++)
  {
    EEPROM.write(addr + i, data[i]);
  }
  EEPROM.write(addr + _size, '\0'); //Add termination null character for String Data
}
String readFromMemory(char addr, int size)
{
  int i;
  char data[size + 1];
  int len = 0;
  unsigned char k;
  k = EEPROM.read(addr);
  while (len < size) //Read until null character
  {
    k = EEPROM.read(addr + len);
    data[len] = k;
    len++;
  }
  data[len] = '\0';
  return String(data);
}

void serialCommunication() {
  if (rs485.available()) {
    incomingByte = rs485.read();
    if (incomingByte == '>') {
      messageCompleted = true;
      newMessage = false;
    }
    else if (incomingByte == '<') {
      newMessage = true;
    }

    if (newMessage) {
      command.concat(incomingByte);
    }
  }

  if (messageCompleted) {
    if (command.substring(1, 3) == PORT || command.substring(1, 3) == "00" ) {
      //Set time
      if (command.charAt(3) == 'T') {
        int YYYY = (command.substring(4, 8)).toInt();
        int MM = (command.substring(8, 10)).toInt();
        int DD = (command.substring(10, 12)).toInt();
        int hh = (command.substring(12, 14)).toInt();
        int mm = (command.substring(14)).toInt();
        setTime(YYYY, MM, DD, hh, mm);
      }
      //Set cards ids
      else if (command.charAt(3) == 'C') {
        int index = (command.substring(4, 5)).toInt();
        String id = command.substring(5);
        cards[index] = id;
        //Store in memory!
        storeInMemory(30 + (index * 10), id); //Start store card id from memory addr 30
      }
    }
    if (command.substring(1, 3) == PORT) {
      //Report time of this slave station to master
      if (command.charAt(3) == 't') {
        digitalWrite(rs485_DE, HIGH);
        rs485.println("<" + MASTER_PORT + "t" + currentTime + ">");
        digitalWrite(rs485_DE, LOW);
      }
      //Report card ids of this slave station to master
      else if (command.charAt(3) == 'c') {
        int index = (command.substring(4,5)).toInt();
        String MSG = "<" + MASTER_PORT + "c"+String(index);
        MSG += cards[index] + ">";
        digitalWrite(rs485_DE, HIGH);
        rs485.println(MSG);
        digitalWrite(rs485_DE, LOW);
      }
      //Report last check to master - time and card id
      else if (command.charAt(3) == 'r') {
        digitalWrite(rs485_DE, HIGH);
        rs485.println("<" + MASTER_PORT + "r" + check_card + " " + check_time + ">");
        digitalWrite(rs485_DE, LOW);
      }
    }
    command = "";
    messageCompleted = false;
  }
}
void loop() {
  serialCommunication();
  checkCard();
  printLCD("Waiting for Card", point);
  readTime();
  if (check != "") {
    printLCD(currentTime, check);
    buzzerTone();
    delay(2000);
  }
}