How exactly have you connected the reader to the Leonardo ? Which pins have you used ? Which serial interface of the Leonardo are you using ? Is it Serial or Serial1 ?
Please post your full sketch, using code tags when you do
In my experience the easiest way to tidy up the code and add the code tags is as follows
Start by tidying up your code by using Tools/Auto Format in the IDE to make it easier to read. Then use Edit/Copy for Forum and paste what was copied in a new reply. Code tags will have been added to the code to make it easy to read in the forum thus making it easier to provide help.
/*
* ----------------------------------------------------------------------------
* This is a MFRC522 library example; see https://github.com/miguelbalboa/rfid
* for further details and other examples.
*
* NOTE: The library file MFRC522.h has a lot of useful info. Please read it.
*
* Released into the public domain.
* ----------------------------------------------------------------------------
* 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.
*
* Typical pin layout used:
* -----------------------------------------------------------------------------------------
* MFRC522 Arduino Arduino Arduino Arduino Arduino
* Reader/PCD Uno 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 //
#define SS_PIN 10 //
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
ShowReaderDetails(); // Show details of PCD - MFRC522 Card Reader details
Serial.println(F("Scan PICC to see UID, type, and data blocks..."));
}
void loop() {
// Look for new cards
if ( ! mfrc522.PICC_IsNewCardPresent()) {
return;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial()) {
return;
}
// Dump debug info about the card; PICC_HaltA() is automatically called
mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
}
void ShowReaderDetails() {
// Get the MFRC522 software version
byte v = mfrc522.PCD_ReadRegister(mfrc522.VersionReg);
Serial.print(F("MFRC522 Software Version: 0x"));
Serial.print(v, HEX);
if (v == 0x91)
Serial.print(F(" = v1.0"));
else if (v == 0x92)
Serial.print(F(" = v2.0"));
else
Serial.print(F(" (unknown)"));
Serial.println("");
// When 0x00 or 0xFF is returned, communication probably failed
if ((v == 0x00) || (v == 0xFF)) {
Serial.println(F("WARNING: Communication failure, is the MFRC522 properly connected?"));
}
}
Thank you for the update
The RC522 reader that you are using has an SPI interface so ignore my questions about the serial interface as they are not relevant