File content as of revision 2:c719944e080b:

#include "mbed.h"
#include "MFRC522.h"

//KL25Z Pins for MFRC522 SPI interface
#define SPI_MOSI    p5
#define SPI_MISO    p6
#define SPI_SCLK    p7
#define SPI_CS      p9
// KL25Z Pin for MFRC522 reset
#define MF_RESET    p8
/**
// KL25Z Pins for Debug UART port
#define UART_RX     gnd
#define UART_TX     gnd

Serial     DebugUART(UART_TX, UART_RX);
**/
MFRC522 RfChip(SPI_MOSI, SPI_MISO, SPI_SCLK, SPI_CS, MF_RESET);
Serial pc(USBTX, USBRX);

DigitalOut led(LED1);

int main(void) {
  pc.printf("Start");
  // Set debug UART speed
  //DebugUART.baud(115200);

  // Init. RC522 Chip
  RfChip.PCD_Init();

  while (true) {
    led = 0;
    // Look for new cards
    if ( ! RfChip.PICC_IsNewCardPresent())
    {
      wait_ms(500);
      continue;
    }

    // Select one of the cards
    if ( ! RfChip.PICC_ReadCardSerial())
    {
      wait_ms(500);
      continue;
    }

    // Print Card UID
    pc.printf("Card UID: ");
    for (uint8_t i = 0; i < RfChip.uid.size; i++)
    {
      led = 1;
      pc.printf(" %X02", RfChip.uid.uidByte[i]);
    }
    pc.printf("\n\r");

    // Print Card type
    uint8_t piccType = RfChip.PICC_GetType(RfChip.uid.sak);
    pc.printf("PICC Type: %s \n\r", RfChip.PICC_GetTypeName(piccType));
    wait_ms(1000);
  }
}