Hello, I'm trying to make a small device that will store the UID value of a RFID card on a SD card.
I have tried to combine two codes to option the following cod but for some unknown reasons it doesn't work for me 
Please help me.
//Libs
#include <Wire.h>
#include <SPI.h>
#include <Adafruit_PN532.h>
#include <SPI.h>
#include <SD.h>
//File
File myFile;
//Define
#define PN532_SCK (2)
#define PN532_MOSI (3)
#define PN532_SS (9)
//4
#define PN532_MISO (5)
//Other
Adafruit_PN532 nfc(PN532_SCK, PN532_MISO, PN532_MOSI, PN532_SS);
//Void
void setup(void)
{
//SD Initialization
Serial.begin(9600);
Serial.print("Initializing SD card...");
if (!SD.begin(4)) {
Serial.println("initialization failed!");
return;
}
Serial.println("initialization done.");
Serial.begin(115200);
Serial.println("PN532 = Lisening");
//NFC Initialization
nfc.begin();
uint32_t versiondata = nfc.getFirmwareVersion();
if (! versiondata) {
Serial.print("Didn't find PN53x board");
while (1); // halt
}
// Got ok data, print it out!
Serial.print("Found chip PN5");
Serial.println((versiondata>>24) & 0xFF, HEX);
Serial.print("Firmware ver. ");
Serial.print((versiondata>>16) & 0xFF, DEC);
Serial.print('.');
Serial.println((versiondata>>8) & 0xFF, DEC);
// configure board to read RFID tags
nfc.SAMConfig();
Serial.println("Waiting for an ISO14443A Card ...");
}
void loop(void)
{
myFile = SD.open("test.txt", FILE_WRITE);
if (myFile)
{
uint8_t success;
uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 }; // Buffer to store the returned UID
uint8_t uidLength; // Length of the UID (4 or 7 bytes depending on ISO14443A card type)
// Wait for an ISO14443A type cards (Mifare, etc.). When one is found
// 'uid' will be populated with the UID, and uidLength will indicate
// if the uid is 4 bytes (Mifare Classic) or 7 bytes (Mifare Ultralight)
success = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid, &uidLength);
if (success) {
// Display some basic information about the card
Serial.println("Found an ISO14443A card");
myFile.println("Found an ISO14443A card");
Serial.print(" UID Length: ");
myFile.print(" UID Length: ");
Serial.print(uidLength, DEC);
myFile.print(uidLength, DEC);
Serial.println(" bytes");
myFile.println(" bytes");
Serial.print(" UID Value: ");
myFile.print(" UID Value: ");
nfc.PrintHex(uid, uidLength);
Serial.println("");
myFile.println("");
if (uidLength == 4)
{
// We probably have a Mifare Classic card ...
Serial.println("Seems to be a Mifare Classic card (4 byte UID)");
myFile.println("Seems to be a Mifare Classic card (4 byte UID)");
// Now we need to try to authenticate it for read/write access
// Try with the factory default KeyA: 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
Serial.println("Trying to authenticate block 4 with default KEYA value");
myFile.println("Trying to authenticate block 4 with default KEYA value");
uint8_t keya[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
// Start with block 4 (the first block of sector 1) since sector 0
// contains the manufacturer data and it's probably better just
// to leave it alone unless you know what you're doing
success = nfc.mifareclassic_AuthenticateBlock(uid, uidLength, 4, 0, keya);
if (success)
{
Serial.println("Sector 1 (Blocks 4..7) has been authenticated");
myFile.println("Sector 1 (Blocks 4..7) has been authenticated");
uint8_t data[16];
// If you want to write something to block 4 to test with, uncomment
// the following line and this text should be read back in a minute
//memcpy(data, (const uint8_t[]){ 'a', 'd', 'a', 'f', 'r', 'u', 'i', 't', '.', 'c', 'o', 'm', 0, 0, 0, 0 }, sizeof data);
// success = nfc.mifareclassic_WriteDataBlock (4, data);
// Try to read the contents of block 4
success = nfc.mifareclassic_ReadDataBlock(4, data);
if (success)
{
// Data seems to have been read ... spit it out
Serial.println("Reading Block 4:");
myFile.println("Reading Block 4:");
nfc.PrintHexChar(data, 16);
Serial.println("");
myFile.println("");
// Wait a bit before reading the card again
delay(1000);
}
else
{
Serial.println("Ooops ... unable to read the requested block. Try another key?");
myFile.println("Ooops ... unable to read the requested block. Try another key?");
}
}
else
{
Serial.println("Ooops ... authentication failed: Try another key?");
myFile.println("Ooops ... authentication failed: Try another key?");
}
}
if (uidLength == 7)
{
// We probably have a Mifare Ultralight card ...
Serial.println("Seems to be a Mifare Ultralight tag (7 byte UID)");
myFile.println("Seems to be a Mifare Ultralight tag (7 byte UID)");
// Try to read the first general-purpose user page (#4)
Serial.println("Reading page 4");
myFile.println("Reading page 4");
uint8_t data[32];
success = nfc.mifareultralight_ReadPage (4, data);
if (success)
{
// Data seems to have been read ... spit it out
nfc.PrintHexChar(data, 4);
Serial.println("");
myFile.println("");
// Wait a bit before reading the card again
delay(1000);
}
else
{
Serial.println("Ooops ... unable to read the requested page!?");
myFile.println("Ooops ... unable to read the requested page!?");
}
}
}
myFile.close();
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
}