user65644: i have a project that use two RFID Reader, the project for counting tag from conveyor belt, in this case the reader will placed in the middle of the conveyor belt and the reader faces each other.
So i have question, can two RFID Reader reading one or many tag simultaneously? I tried before but when i tried to scan, the two readers did not respond, but if i scan one tag and one reader it will work correctly.
For example:
i have readers 0 and readers 1, and two variables count0 and count1, remember the readers faces each others, so i put one tag in the middle of reader0 and reader1, if the reader 0 scan the tag, count0 will increase to 1 and if reader 1 scan the tag in the SAME TIME it wouldn’t be counting because the reader 0 has scan that tag.
but in my case, the readers(0 and 1) didnt response if i put the tag in the middle of readers.
i use this tutorial for my project https://youtu.be/HmGmFknAIqc
and for this project the data count0 and count1 i send it to nodemcu using SoftwareSerial(5,6).
Im new for using Arduino and i still learn about it(i dont understand too much)
Heres my arduino code
/**
 * --------------------------------------------------------------------------------------------------------------------
 * Example sketch/program showing how to read data from more than one PICC to serial.
 * --------------------------------------------------------------------------------------------------------------------
 * This is a MFRC522 library example; for further details and other examples see: https://github.com/miguelbalboa/rfid
 *
 * Example sketch/program showing how to read data from more than one PICC (that is: a RFID Tag or Card) using a
 * MFRC522 based RFID Reader on the Arduino SPI interface.
 *
 * Warning: This may not work! Multiple devices at one SPI are difficult and cause many trouble!! Engineering skill
 *          and knowledge are required!
 *
 * @license Released into the public domain.
 *
 * Typical pin layout used:
 * -----------------------------------------------------------------------------------------
 *             MFRC522      Arduino       Arduino   Arduino    Arduino          Arduino
 *             Reader/PCD   Uno/101       Mega      Nano v3    Leonardo/Micro   Pro Micro
 * Signal      Pin          Pin           Pin       Pin        Pin              Pin
 * -----------------------------------------------------------------------------------------
 * RST/Reset   RST          9             5         D9         RESET/ICSP-5     RST
 * SPI SS 1    SDA(SS)      ** custom, take a unused pin, only HIGH/LOW required **
 * SPI SS 2    SDA(SS)      ** custom, take a unused pin, only HIGH/LOW required **
 * SPI MOSI    MOSI         11 / ICSP-4   51        D11        ICSP-4           16
 * SPI MISO    MISO         12 / ICSP-1   50        D12        ICSP-1           14
 * SPI SCK     SCK          13 / ICSP-3   52        D13        ICSP-3           15
 *
 */
#include <Wire.h>
#include <SPI.h>
#include <MFRC522.h>
#include <SoftwareSerial.h>
#include <LiquidCrystal_I2C.h> //library penampil LCD

#define RST_PIN         9          // Configurable, see typical pin layout above
#define SS_1_PIN        10         // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 2
#define SS_2_PIN        8          // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 1

#define NR_OF_READERS   2

LiquidCrystal_I2C lcd(0x27,20,4); //0x3f dapat dicari dengan i2c scanner
SoftwareSerial s(5,6);
//SoftwareSerial s1(2,3);


byte ssPins[] = {SS_1_PIN, SS_2_PIN};

MFRC522 mfrc522[NR_OF_READERS];   // Create MFRC522 instance.
int i = 1;
byte code[10];
String uidString;
int count0 = 0;
int count1 = 0;


/**
 * Initialize.
 */
void setup() {
  s.begin(9600);
 // s1.begin(9600);
  Serial.begin(9600); // Initialize serial communications with the PC
  while (!Serial);
  SPI.begin();        // Init SPI bus

  for (uint8_t reader = 0; reader < NR_OF_READERS; reader++) {
    mfrc522[reader].PCD_Init(ssPins[reader], RST_PIN); // Init each MFRC522 card
    Serial.print(F("Reader "));
    Serial.print(reader);
    Serial.print(F(": "));
    mfrc522[reader].PCD_DumpVersionToSerial();
  }

//  lcd.init();
//  lcd.init();
//  lcd.backlight(); //menghidupkan lampu latar LCD
//  lcd.setCursor (3,0);
//  lcd.print("Final Project");
//  delay (1000);
//  lcd.clear();
}

/**
 * Main loop.
 */
void loop() {
//  lcd.setCursor (0,0);
//  lcd.print("SCAN RFID");

  for (uint8_t reader = 0; reader < NR_OF_READERS; reader++) {
    // Look for new cards
    if(reader == 0){
      reader0(reader);
    }else if(reader == 1){
      reader1(reader);
    }      
  }
}

/** SCAN RFID TAG READER0 */
void reader0(int reader){
    if (mfrc522[reader].PICC_IsNewCardPresent() && mfrc522[reader].PICC_ReadCardSerial()) {
      Serial.println();
      Serial.print(F("Reader "));
      Serial.print(reader);
      // Show some details of the PICC (that is: the tag/card)
      Serial.println();
      Serial.print(F("Card UID = "));
      dump_byte_array(mfrc522[reader].uid.uidByte, mfrc522[reader].uid.size);
      Serial.println();
//      Serial.print(F("PICC type: "));
//      MFRC522::PICC_Type piccType = mfrc522[reader].PICC_GetType(mfrc522[reader].uid.sak);
//      Serial.println(mfrc522[reader].PICC_GetTypeName(piccType));
      count0++;
      lcd.setCursor (0,0);

      Serial.print("Counter ");
      Serial.print(reader);
      Serial.print(" = ");
      Serial.print(count0);
      Serial.println();
      s.write(count0);
       }

      mfrc522[reader].PICC_HaltA();
      mfrc522[reader].PCD_StopCrypto1();   
}

/** SCAN RFID TAG READER1 */
void reader1(int reader){
    if (mfrc522[reader].PICC_IsNewCardPresent() && mfrc522[reader].PICC_ReadCardSerial()) {
      Serial.println();
      Serial.print(F("Reader "));
      Serial.print(reader);
      Serial.println();
      // Show some details of the PICC (that is: the tag/card)
      Serial.print(F("Card UID = "));
      dump_byte_array(mfrc522[reader].uid.uidByte, mfrc522[reader].uid.size);
      Serial.println();
//      Serial.print(F("PICC type: "));
//      MFRC522::PICC_Type piccType = mfrc522[reader].PICC_GetType(mfrc522[reader].uid.sak);
//      Serial.println(mfrc522[reader].PICC_GetTypeName(piccType));
      count1++;
      lcd.setCursor (0,0);

      Serial.print("Counter ");
      Serial.print(reader);
      Serial.print(" = ");
      Serial.print(count1);
      Serial.println();
      s.write(count1);
    }

      mfrc522[reader].PICC_HaltA();
      // Stop encryption on PCD
      mfrc522[reader].PCD_StopCrypto1();      
}

/**
 * Helper routine to dump a byte array as hex values to Serial.
 */
void dump_byte_array(byte *buffer, byte bufferSize) {
  for (byte i = 0; i < bufferSize; i++) {
    Serial.print(buffer[i] < 0x10 ? " 0" : " ");
    Serial.print(buffer[i], HEX);
  }
}

anyway sorry for my bad english :D

user69619: Take a look at this this link it might be of a help to you. It uses four RFID readers at the same time

user71300: I'm just starting a project using RFID tags to track cars and engines on a model railroad.
Although I haven't gotten very far yet, my first thought was to use a multiplexer to select which reader I receive data from at any given time. It won't be simultaneous but I should be able to read a dozen or more per second which is probably enough.

65644: <p>i have a project that use two RFID Reader, the project for counting tag from conveyor belt, in this case the reader will placed in the middle of the conveyor belt and the reader faces each other.</p>

<p>So i have question, can two RFID Reader reading one or many tag simultaneously? I tried before but when i tried to scan, the two readers did not respond, but if i scan one tag and one reader it will work correctly.</p>

<p>For example:
i have readers 0 and readers 1, and two variables count0 and count1, remember the readers faces each others, so i put one tag in the middle of reader0 and reader1, if the reader 0 scan the tag, count0 will increase to 1 and if reader 1 scan the tag in the SAME TIME it wouldn’t be counting because the reader 0 has scan that tag.</p>

<p>but in my case, the readers(0 and 1) didnt response if i put the tag in the middle of readers.</p>

<p>i use this tutorial for my project <a href="https://youtu.be/HmGmFknAIqc" rel="nofollow noreferrer">https://youtu.be/HmGmFknAIqc</a></p>

<p>and for this project the data count0 and count1 i send it to nodemcu using SoftwareSerial(5,6).</p>

<p>Im new for using Arduino and i still learn about it(i dont understand too much)</p>

<p>Heres my arduino code</p>

<pre><code>/**
 * --------------------------------------------------------------------------------------------------------------------
 * Example sketch/program showing how to read data from more than one PICC to serial.
 * --------------------------------------------------------------------------------------------------------------------
 * This is a MFRC522 library example; for further details and other examples see: https://github.com/miguelbalboa/rfid
 *
 * Example sketch/program showing how to read data from more than one PICC (that is: a RFID Tag or Card) using a
 * MFRC522 based RFID Reader on the Arduino SPI interface.
 *
 * Warning: This may not work! Multiple devices at one SPI are difficult and cause many trouble!! Engineering skill
 *          and knowledge are required!
 *
 * @license Released into the public domain.
 *
 * Typical pin layout used:
 * -----------------------------------------------------------------------------------------
 *             MFRC522      Arduino       Arduino   Arduino    Arduino          Arduino
 *             Reader/PCD   Uno/101       Mega      Nano v3    Leonardo/Micro   Pro Micro
 * Signal      Pin          Pin           Pin       Pin        Pin              Pin
 * -----------------------------------------------------------------------------------------
 * RST/Reset   RST          9             5         D9         RESET/ICSP-5     RST
 * SPI SS 1    SDA(SS)      ** custom, take a unused pin, only HIGH/LOW required **
 * SPI SS 2    SDA(SS)      ** custom, take a unused pin, only HIGH/LOW required **
 * SPI MOSI    MOSI         11 / ICSP-4   51        D11        ICSP-4           16
 * SPI MISO    MISO         12 / ICSP-1   50        D12        ICSP-1           14
 * SPI SCK     SCK          13 / ICSP-3   52        D13        ICSP-3           15
 *
 */
#include &lt;Wire.h&gt;
#include &lt;SPI.h&gt;
#include &lt;MFRC522.h&gt;
#include &lt;SoftwareSerial.h&gt;
#include &lt;LiquidCrystal_I2C.h&gt; //library penampil LCD

#define RST_PIN         9          // Configurable, see typical pin layout above
#define SS_1_PIN        10         // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 2
#define SS_2_PIN        8          // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 1

#define NR_OF_READERS   2

LiquidCrystal_I2C lcd(0x27,20,4); //0x3f dapat dicari dengan i2c scanner
SoftwareSerial s(5,6);
//SoftwareSerial s1(2,3);


byte ssPins[] = {SS_1_PIN, SS_2_PIN};

MFRC522 mfrc522[NR_OF_READERS];   // Create MFRC522 instance.
int i = 1;
byte code[10];
String uidString;
int count0 = 0;
int count1 = 0;


/**
 * Initialize.
 */
void setup() {
  s.begin(9600);
 // s1.begin(9600);
  Serial.begin(9600); // Initialize serial communications with the PC
  while (!Serial);
  SPI.begin();        // Init SPI bus

  for (uint8_t reader = 0; reader &lt; NR_OF_READERS; reader++) {
    mfrc522[reader].PCD_Init(ssPins[reader], RST_PIN); // Init each MFRC522 card
    Serial.print(F("Reader "));
    Serial.print(reader);
    Serial.print(F(": "));
    mfrc522[reader].PCD_DumpVersionToSerial();
  }

//  lcd.init();
//  lcd.init();
//  lcd.backlight(); //menghidupkan lampu latar LCD
//  lcd.setCursor (3,0);
//  lcd.print("Final Project");
//  delay (1000);
//  lcd.clear();
}

/**
 * Main loop.
 */
void loop() {
//  lcd.setCursor (0,0);
//  lcd.print("SCAN RFID");

  for (uint8_t reader = 0; reader &lt; NR_OF_READERS; reader++) {
    // Look for new cards
    if(reader == 0){
      reader0(reader);
    }else if(reader == 1){
      reader1(reader);
    }      
  }
}

/** SCAN RFID TAG READER0 */
void reader0(int reader){
    if (mfrc522[reader].PICC_IsNewCardPresent() &amp;&amp; mfrc522[reader].PICC_ReadCardSerial()) {
      Serial.println();
      Serial.print(F("Reader "));
      Serial.print(reader);
      // Show some details of the PICC (that is: the tag/card)
      Serial.println();
      Serial.print(F("Card UID = "));
      dump_byte_array(mfrc522[reader].uid.uidByte, mfrc522[reader].uid.size);
      Serial.println();
//      Serial.print(F("PICC type: "));
//      MFRC522::PICC_Type piccType = mfrc522[reader].PICC_GetType(mfrc522[reader].uid.sak);
//      Serial.println(mfrc522[reader].PICC_GetTypeName(piccType));
      count0++;
      lcd.setCursor (0,0);

      Serial.print("Counter ");
      Serial.print(reader);
      Serial.print(" = ");
      Serial.print(count0);
      Serial.println();
      s.write(count0);
       }

      mfrc522[reader].PICC_HaltA();
      mfrc522[reader].PCD_StopCrypto1();   
}

/** SCAN RFID TAG READER1 */
void reader1(int reader){
    if (mfrc522[reader].PICC_IsNewCardPresent() &amp;&amp; mfrc522[reader].PICC_ReadCardSerial()) {
      Serial.println();
      Serial.print(F("Reader "));
      Serial.print(reader);
      Serial.println();
      // Show some details of the PICC (that is: the tag/card)
      Serial.print(F("Card UID = "));
      dump_byte_array(mfrc522[reader].uid.uidByte, mfrc522[reader].uid.size);
      Serial.println();
//      Serial.print(F("PICC type: "));
//      MFRC522::PICC_Type piccType = mfrc522[reader].PICC_GetType(mfrc522[reader].uid.sak);
//      Serial.println(mfrc522[reader].PICC_GetTypeName(piccType));
      count1++;
      lcd.setCursor (0,0);

      Serial.print("Counter ");
      Serial.print(reader);
      Serial.print(" = ");
      Serial.print(count1);
      Serial.println();
      s.write(count1);
    }

      mfrc522[reader].PICC_HaltA();
      // Stop encryption on PCD
      mfrc522[reader].PCD_StopCrypto1();      
}

/**
 * Helper routine to dump a byte array as hex values to Serial.
 */
void dump_byte_array(byte *buffer, byte bufferSize) {
  for (byte i = 0; i &lt; bufferSize; i++) {
    Serial.print(buffer[i] &lt; 0x10 ? " 0" : " ");
    Serial.print(buffer[i], HEX);
  }
}
</code></pre>

<p>anyway sorry for my bad english :D</p>
 69619: <p>Take a look at this <a href="https://www.youtube.com/watch?v=ahc8Yai_sWI" rel="nofollow noreferrer">this link</a> it might be of a help to you. It uses four RFID readers at the same time</p>
 71300: <p>I'm just starting a project using RFID tags to track cars and engines on a model railroad.
Although I haven't gotten very far yet, my first thought was to use a multiplexer to select which reader I receive data from at any given time. It won't be simultaneous but I should be able to read a dozen or more per second which is probably enough.</p>
