RFID Domination Timer

Advantages of the system

List of supported hardware (PCB compatible):

• Arduino Nano V3.0
• LCD 2004A (20x4) with I2C converter, 5V operated
• NXP RFID RC522 (13.56 MHz), 3V3 operated
• ISO/IEC 14443-A RFID wristbands, cards (MiFare 1K tags - 13.56 MHz)
• Buzzer, 7.62 mm pitch, 5V operated
• 5mm LEDs
• THT resistors (220Ω up to 1K based on LED color)



Possible swaps:

• Uno, or standalone AVR ATmega328P chip with external 16 MHz oscillator - not compatible with PCB design



Other components:

• Pullup THT resistors for I2C bus: SDA, SCL signals (10K)
• Standoff Spacer Screws, 10 mm base + 6 mm M3 thread (plastic / brass) / threaded rod can be used (if unit mounted on the wall)
• Custom 3D printed enclosure 124 x 123 x 46 mm
• 25 mm Tie-down belt / strap
• Phillips screwdriver Ø 3 mm (to be able to set contrast through the 3D printed PLA enclosure ingame)

RFID DOMINATOR - source code:

Minimal version, 1 card per team, no buzzer, only for 20x4 LCD screen

 
//RFID DOMINATOR 2.0 - Domination Timer for Airsoft, USAGE UNDER MIT LICENSE!
//BLUE AND YELLOW TEAM, MINIMAL FUNCTIONALITY, ONE CARD / WRISTBAND PER TEAM
//BUZZER NOT INCLUDED, only 20x4 LCD screen supported
//Author: Martin Chlebovec (martinius96@gmail.com)
//Revision --> 20th February 2026
//Project info: https://your-iot.github.io/DOMINATOR/

//Installation instructions:
//Download library MFRC522 from: https://github.com/miguelbalboa/rfid/releases/tag/1.4.11 (Click on Source code (zip))
//Download library LiquidCrystal_I2C from: https://github.com/fdebrabander/Arduino-LiquidCrystal-I2C-library (click on Code --> Download ZIP)

//Open .zip and copy whole directory into C:/Users/[actual user]/Documents/Arduino/libraries
//Now you can compile this source code

//For Arduino Nano with Old Bootloader, navigate to Tools --> Board --> Arduino Nano
//Tools --> Processor --> ATMega328P (Old Bootloader) - that will reduce upload speed to 57600 baud/s
//Standardly all Arduino Nano V3.0 has Old Bootloader (Blue clones)
//For standard bootloader nothing is required to set, only Arduino Nano under Tools --> Board (default)

#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <Wire.h>
#include <MFRC522.h>

//Pinout compatible for Arduino Nano with MFRC522 (NXP RC522) on RFID DOMINATOR 2.0 PCB board
#define SS_PIN 10
#define RST_PIN 9

MFRC522 rfid(SS_PIN, RST_PIN);

//Known RFID cards UIDs based on teams (You can see UID of your cards in Serial monitor when attached)
const unsigned long TEAM_BLU = 4321; //BLUE TEAM UID --> BLUE CARD
const unsigned long TEAM_YEL = 17933; //YELLOW TEAM UID --> YELLOW CARD
const unsigned long TEAM_REFEREE = 7921; //REFEREE GROUP UID --> GREEN CARD
const unsigned long TEAM_ERASER = 4294948592; //ERASER GROUP UID --> RED CARD

unsigned long code; //UID --> RFID CARD ADDRESS
boolean run = false; //is BLU team active on DOMINATION TIMER?
boolean run2 = false; //is YEL team active on DOMINATION TIMER?

unsigned long timer = 0; //timer 32-bit - GAME TIMER
unsigned long timer2 = 0; //timer 32-bit - RFID CHECK TIMER


boolean once = false; //was once-timed action created yet?
//TIME RELATED VARIABLES FOR TEAM RED
int second = 0; //seconds of team RED
int minute = 0; //minutes of team RED
int hour = 0;   //hours of team RED

//TIME RELATED VARIABLES FOR TEAM GRE
int second2 = 0; //seconds of team GRE
int minute2 = 0; //minutes of team GRE
int hour2 = 0; //hours of team GRE

//OUTPUTS
const int BLU_LED = 6; //LED for team RED
const int RED_LED = 4; //LED for team GRE
const int ORA_LED = 7; //LED for team RED
const int GRE_LED = 3; //LED for team GRE

LiquidCrystal_I2C* lcd;

//user-defined functions declaration
void updateLCD();
void updateLCD2();
void tickClock();
void tick();
byte error, address;
void setup() {
  Serial.begin(9600); //Start UART bus at 9600 baud/s
  Serial.println(F("RFID Domination Timer 2.0 - freeware 9th February 2026"));
  Serial.println(F("Creator: Martin Chlebovec (martinius96@gmail.com)"));
  Serial.println(F("Project info: https://your-iot.github.io/DOMINATOR/"));
  SPI.begin(); //Standard SPI speed for RC522 --> 4 MHz
  Wire.begin(); //Standard I2C speed for LCD screen --> 100 kHz
  for (address = 1; address < 127; address++ ) //this cycle will scan I2C bus and set LCD display automatically with any I2C address
  {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();
    if (error == 0)
    {
      Serial.print("I2C device found at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println("  !");
      break;
    }
  }
  lcd = new LiquidCrystal_I2C(address, 20, 4); //display initialization
  pinMode(BLU_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(ORA_LED, OUTPUT);
  pinMode(GRE_LED, OUTPUT);
  rfid.PCD_Init(); // Init MFRC522
  rfid.PCD_SetAntennaGain(rfid.RxGain_max);
  rfid.PCD_DumpVersionToSerial(); //Write version of Firmware to UART
  lcd->begin(); //Not valid for Wokwi simulator, valid for LiquidCrystal_I2C library from @fdebrabander
  lcd->backlight(); //backlight on
  lcd->clear();
  lcd->setCursor(0, 0);
  lcd->print(F(" RFID DOMINATOR 2.0 "));
  lcd->setCursor(0, 2);
  lcd->print(F("   DEVELOPED  BY:   "));
  lcd->setCursor(0, 3);
  lcd->print(F("  Martin Chlebovec  "));

  for (int i = 0; i < 20; i++) {
    // LED animation effect, loading
    switch (i % 4) {
      case 0:
        digitalWrite(BLU_LED, HIGH);
        delay(250);
        digitalWrite(BLU_LED, LOW);
        break;
      case 1:
        digitalWrite(GRE_LED, HIGH);
        delay(250);
        digitalWrite(GRE_LED, LOW);
        break;
      case 2:
        digitalWrite(RED_LED, HIGH);
        delay(250);
        digitalWrite(RED_LED, LOW);
        break;
      case 3:
        digitalWrite(ORA_LED, HIGH);
        delay(250);
        digitalWrite(ORA_LED, LOW);
        break;
    }

    //print loading bar
    lcd->setCursor(i, 1);
    lcd->write(byte(255)); // plný znak
  }
  delay(500);
  lcd->clear();
  lcd->setCursor(0, 0);
  lcd->print(F("BLU 00:00:00")); //BLUE TEAM IN ROW 1
  lcd->setCursor(0, 1);
  lcd->print(F("YEL 00:00:00")); //YELLOW TEAM IN ROW 2
  lcd->setCursor(0, 2);
  lcd->print(F("  Martin Chlebovec  "));
  lcd->setCursor(0, 3);
  lcd->print(F(" RFID DOMINATOR 2.0 "));
}

void loop() {
  tickClock();
  if ((millis() - timer2) >= 300) { //Check for incomming datas from RC522 reader each 300 ms
    timer2 = millis();
    if (rfid.PICC_IsNewCardPresent() && rfid.PICC_ReadCardSerial()) {
      dump_byte_array(rfid.uid.uidByte, rfid.uid.size);
      rfid.PICC_HaltA();
      rfid.PCD_StopCrypto1();

      if (code == TEAM_BLU) { // WAS CARD FROM TEAM BLUE?
        if (!run) {
          timer = millis();
        }
        Serial.println(F("Detected card from team BLU"));
        digitalWrite(BLU_LED, HIGH);
        digitalWrite(RED_LED, LOW);
        digitalWrite(ORA_LED, LOW);
        digitalWrite(GRE_LED, LOW);
        run = true;
        run2 = false;
      }

      if (code == TEAM_YEL) { //WAS CARD FROM TEAM YELLOW?
        if (!run2) {
          timer = millis();
        }
        Serial.println(F("Detected card from team YEL"));
        digitalWrite(BLU_LED, LOW);
        digitalWrite(RED_LED, LOW);
        digitalWrite(ORA_LED, HIGH);
        digitalWrite(GRE_LED, LOW);
        run = false;
        run2 = true;
      }

      if (code == TEAM_REFEREE) { //WAS CARD FROM TEAM REFEREE?
        Serial.println(F("Detected card from REFEREE"));
        digitalWrite(BLU_LED, LOW);
        digitalWrite(RED_LED, LOW);
        digitalWrite(ORA_LED, LOW);
        digitalWrite(GRE_LED, LOW);
        run = false;
        run2 = false;
      }

      if (code == TEAM_ERASER) { //WAS CARD FROM TEAM ERASER?
        Serial.println(F("Detected card from ERASER"));
        digitalWrite(BLU_LED, LOW);
        digitalWrite(RED_LED, LOW);
        digitalWrite(ORA_LED, LOW);
        digitalWrite(GRE_LED, LOW);
        //Zero each value for times
        second = 0;
        minute = 0;
        hour = 0;
        second2 = 0;
        minute2 = 0;
        hour2 = 0;
        updateLCD();
        updateLCD2();
        //Stop active team
        run = false;
        run2 = false;
      }
    }
  }
}

void tickClock() {
  if ((millis() - timer) >= 1000) { //Timer for counting time each 1000 ms (second resolution)
    timer = millis();
    //Serial.println(timer); //UNCOMMENT TO GET TIMER PRECISION INFO, if couting in 1000 ms or more
    if (once == false) {
      timer2 = millis();
      once = true;
    }
    error = Wire.endTransmission(); //check, if display was disconnected during operation, if yes, that will renew is connection and initialization
    if (error != 0) {
      Serial.println("Display is not communicating");
      // Communication error, re-initialize the communication with the LCD
      lcd->begin(); //Not valid for Wokwi simulator, valid for LiquidCrystal_I2C library from @fdebrabander
      lcd->backlight();
      lcd->setCursor(0, 0);
      lcd->print(F("BLU   :  :  ")); //BLU TEAM IN ROW 1
      updateLCD();
      lcd->setCursor(0, 1);
      lcd->print(F("YEL   :  :  ")); //YEL TEAM IN ROW 2
      updateLCD2();
    }
    tick();
    tick2();
  }

}
void tick() {
  if (run) {
    //  updateLCD(); //print team 1 numbers (BLUE)
    second++;
    if (second >= 60)
    {
      second = 0;
      minute++;
      if (minute >= 60)
      {
        minute = 0;
        hour++;
      }
    }
    updateLCD();
  }
}

void tick2() {
  if (run2) {
    //   updateLCD2(); //print team 2 numbers (YELLOW)
    second2++;
    if (second2 >= 60)
    {
      second2 = 0;
      minute2++;
      if (minute2 >= 60)
      {
        minute2 = 0;
        hour2++;
      }
    }
    updateLCD2();
  }
}

void updateLCD() {
  lcd->setCursor(4, 0);
  if (hour < 10) {
    lcd->print(F("0"));
  }
  lcd->print(hour, DEC);
  lcd->setCursor(7, 0);
  if (minute < 10) {
    lcd->print(F("0"));
  }
  lcd->print(minute, DEC);
  lcd->setCursor(10, 0);
  if (second < 10) {
    lcd->print(F("0"));
  }
  lcd->print(second, DEC);
}

void updateLCD2() {
  lcd->setCursor(4, 1);
  if (hour2 < 10) {
    lcd->print(F("0"));
  }
  lcd->print(hour2, DEC);
  lcd->setCursor(7, 1);
  if (minute2 < 10) {
    lcd->print(F("0"));
  }
  lcd->print(minute2, DEC);
  lcd->setCursor(10, 1);
  if (second2 < 10) {
    lcd->print(F("0"));
  }
  lcd->print(second2, DEC);
}


void dump_byte_array(byte *buffer, byte bufferSize) {
  for (byte i = 0; i < bufferSize; i++) {
  }
  Serial.print(F("Detected UID (code) of RFID CARD: "));
  code = 10000 * buffer[4] + 1000 * buffer[3] + 100 * buffer[2] + 10 * buffer[1] + buffer[0]; //Final UID (reverse order, byte 5 as MSB
  Serial.println(code); //UID
}