It's works for me: #include <SPI.h> #include <MFRC522.h> #define MISO_PIN 12 #define MOSI_PIN 13 #define SCK_PIN 14 #define SS_PIN 15 #define RST_PIN 16 MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance void setup() { delay(2000); Serial.begin(115200); // Initialize serial communications ...