I am using this library https://github.com/miguelbalboa/rfid, and using DumpInfo.ino from it:

 * --------------------------------------------------------------------------------------------------------------------
 * Example sketch/program showing how to read data from a 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 a PICC (that is: a RFID Tag or Card) using a MFRC522 based RFID
 * Reader on the Arduino SPI interface.
 * When the Arduino and the MFRC522 module are connected (see the pin layout below), load this sketch into Arduino IDE
 * then verify/compile and upload it. To see the output: use Tools, Serial Monitor of the IDE (hit Ctrl+Shft+M). When
 * you present a PICC (that is: a RFID Tag or Card) at reading distance of the MFRC522 Reader/PCD, the serial output
 * will show the ID/UID, type and any data blocks it can read. Note: you may see "Timeout in communication" messages
 * when removing the PICC from reading distance too early.
 * If your reader supports it, this sketch/program will read all the PICCs presented (that is: multiple tag reading).
 * So if you stack two or more PICCs on top of each other and present them to the reader, it will first output all
 * details of the first and then the next PICC. Note that this may take some time as all data blocks are dumped, so
 * keep the PICCs at reading distance until complete.
 * @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      SDA(SS)      10            53        D10        10               10
 * 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 <SPI.h>
#include <MFRC522.h>

#define RST_PIN         9          // Configurable, see typical pin layout above
#define SS_PIN          10         // Configurable, see typical pin layout above

MFRC522 mfrc522(SS_PIN, RST_PIN);  // Create MFRC522 instance

void setup() {
    Serial.begin(9600);     // Initialize serial communications with the PC
    while (!Serial);        // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
    SPI.begin();            // Init SPI bus
    mfrc522.PCD_Init();     // Init MFRC522
    mfrc522.PCD_DumpVersionToSerial();  // Show details of PCD - MFRC522 Card Reader details
    Serial.println(F("Scan PICC to see UID, SAK, type, and data blocks..."));

void loop() {
    // Look for new cards
    if ( ! mfrc522.PICC_IsNewCardPresent()) {

    // Select one of the cards
    if ( ! mfrc522.PICC_ReadCardSerial()) {

    // Dump debug info about the card; PICC_HaltA() is automatically called

When I connect everything correctly and upload that sketch, this shows up in my Serial Monitor: serial monitor not working rfid

I have tried this with another cheap Arduino Uno, I connected it exactly the same and scanned one card, everything works perfectly fine: serial monitor working rfid

So I guess RC522 module is working fine, and there is probably issue with that Arduino Uno board.

What I tried next without any success is:

  • Copy bootloader from working Arduino Uno to this Arduino Uno that is not working.
  • Switch ATMEGA328P from working Arduino Uno to this Arduino Uno that is not working.

I tested all pins (on board that is not working) for PWM and Digital Output functionality with Firmata Test, and everything is fine in this test.

You can take a look on images of this Arduino Uno board here.

So my question is: something is wrong with the board itself or I am doing something wrong?


  • reduce you sketch to the minimum code required to demonstrate the failure and post the sketch – jsotola Jan 19 at 21:16
  • @jsotola I posted a code that I am using. I think I can't reduce it, its example code from RC522 library. What confuses me the most is that why the code is not working on that Arduino Uno but works perfectly fine on another very identical Arduino Uno. – M. Pezo Jan 20 at 13:17
  • thanks for including the code .... actually, you can reduce the code .... delete everything in the loop() block .... the failure already exists in setup() ............ please recheck your wiring ...... if you are using a breadboard, then rebuild the circuit on another part of the breadboard – jsotola Jan 20 at 18:57
  • @jsotola I reduced a code as you say and checked wiring (I am using a direct connection from module to a reader with a female to male cables), still same results. – M. Pezo Jan 20 at 22:36

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