nodemcu_esp8266_keypad_em18.ino

#include <Keypad.h>
 
const byte n_rows = 4;
const byte n_cols = 4;
 
char keys[n_rows][n_cols] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
 
byte colPins[n_rows] = {0, 4, 5, 16}; //connect to the row pinouts of the keypad
byte rowPins[n_cols] = {13, 12, 14, 2}; //connect to the column pinouts of the keypad
 
//initialize an instance of class NewKeypad
Keypad myKeypad = Keypad( makeKeymap(keys), rowPins, colPins, n_rows, n_cols);

int count = 0; 
char c; 
String id;

void setup(){
  Serial.begin(115200);
}

void loop(){
  char myKey = myKeypad.getKey();
 
  if (myKey != NULL){
    Serial.print("Key pressed: ");
    Serial.println(myKey);
  }

  while(Serial.available()>0)
    {
     c = Serial.read();
     count++;
     id += c;
     if(count == 12)  
      {
        Serial.print("RFID ID:");
        Serial.println(id);
        break; 
      }
    }
  id="";
}