Writing to Mifare Ultralight C with PN532 library for Arduino Uno

Question

I use the sample code to read from MIFARE Ultralight and write to MIFARE Classic, with the definition in .h file:

#define PN532_RESPONSE_INDATAEXCHANGE       (0x41)
#define MIFARE_CMD_WRITE                    (0xA0)

but when I run the code below:

/**************************************************************************/
uint8_t PN532::mifareultralight_WritePage (uint8_t page, uint8_t *buffer1)
{
    /* Prepare the first command */
    pn532_packetbuffer[0] = PN532_COMMAND_INDATAEXCHANGE;
    pn532_packetbuffer[1] = 1;                      /* Card number */
    pn532_packetbuffer[2] = MIFARE_CMD_WRITE;       /* Mifare Write command = 0xA0 */
    pn532_packetbuffer[3] = page;                   /* Page Number (0..63 in most cases) */
    memcpy (pn532_packetbuffer + 4, buffer1, 4);        /* Data Payload */

    /* Send the command */
    if (HAL(writeCommand)(pn532_packetbuffer, 8)) {
        Serial.println(F("Go here 1"));
        return 0;
    }
    Serial.println(F("Go here 2"));
    /* Read the response packet */
    return (0 < HAL(readResponse)(pn532_packetbuffer, sizeof(pn532_packetbuffer)));
}

The result would be like this:

Scan a NFC tag

write:  4A 1 0
read:   4B 1 1 0 44 0 7 4 C1 37 CA 2C 2C 80
ATQA: 0x 44SAK: 0x 0
Writing Mifare Ultralight
write:  40 1 30 4
read:   41 0 2 0 0 10 0 6 1 10 11 FF 0 0 0 0 0 0
write:  40 1 30 3
read:   41 0 0 0 0 0 2 0 0 10 0 6 1 10 11 FF 0 0
Tag capacity 0 bytes
write:  40 1 A0 5 1 2 3 4
Go here 2
Write failed 0

It does not go into "Go here 1", it means that no write command to the reader, do anyone know why?

Answer 1

That write command you are using seems to be wrong. You are using the COMPATIBILITY_WRITE command code (0xA0) but you pass the parameters of a WRITE command.

I suggest you stick to the WRITE command:

+-----------+------+------+---------------------+
| WRAPPING  | CMD  | ADDR | DATA (1 PAGE)       |
+-----------+------+------+---------------------+
| 0x40 0x01 | 0xA2 | 0x05 | 0x01 0x02 0x03 0x04 |
+-----------+------+------+---------------------+

Or you could also use the COMPATIBILITY_WRITE command:

1. You start with sending the command and the address:

   +-----------+------+------+
   | WRAPPING  | CMD  | ADDR |
   +-----------+------+------+
   | 0x40 0x01 | 0xA0 | 0x05 |
   +-----------+------+------+
   

   You should then receive the ACK/NAK status from the tag.

2. Then you send the data in a second frame:

   +-----------+---------------------+------------------------------------------------------------+
   | WRAPPING  | DATA (1 PAGE)       | FILLER (3 EMPTY PAGES)
   +-----------+---------------------+------------------------------------------------------------+
   | 0x40 0x01 | 0x01 0x02 0x03 0x04 | 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
   +-----------+---------------------+------------------------------------------------------------+