Getting strange answer from PN532 with raspberry pi

Question

after I send command to adafruit PN532:

00 00 ff 03 fd d4 14 01 17 00

I get answer:

00 00 C3 BF 00 C3 BF 00 00 00 C3 BF 02 C3 BE C3 95 15 16 00

Instead of:

00 00 ff 00 ff 00 00 00 ff 02 fe d5 15 16 00

I am communicating with PN532 using uart through serial port "/dev/ttyAMA0" I have code in Java. Reading from GPIO using pi4j. Do you know why I am getting this kind of mishmashed answer?

Here is my code:

public class NFCapp {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    byte[] SAMConfiguration = {(byte) 0x00, (byte) 0x00, (byte) 0xff, (byte) 0x03, (byte) 0xfd, (byte) 0xd4, (byte) 0x14, (byte) 0x01, (byte) 0x17, (byte) 0x00};
    byte[] wakeUP = {(byte) 0x55, (byte) 0x55, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00};
    final byte[] ack = {(byte) 0x00, (byte) 0x00, (byte) 0xff, (byte) 0x00, (byte) 0xff, (byte) 0x00};
    final Serial serial = SerialFactory.createInstance();
    try {


        serial.open("/dev/ttyAMA0", 115200);
        serial.addListener(new SerialDataListener() {
            @Override
            public void dataReceived(SerialDataEvent event) {
                String data = event.getData();
                StringBuilder buffer = new StringBuilder();
                byte[] array = data.getBytes();

                System.out.println("Read: ");
                for (int i = 0; i < array.length; i++) {
                    System.out.printf("%02X ", array[i]);
                }
                serial.write(ack);
            }
        });
        System.out.println("Port Opened: " + serial.isOpen() + " ");
        serial.write(wakeUP);
        System.out.print("Write: ");
        for (int i = 0; i < SAMConfiguration.length; i++) {
            System.out.printf("%02X ", SAMConfiguration[i]);
        }
        System.out.println();
        serial.write(SAMConfiguration);

        for (;;) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException ex) {
                System.out.println(ex.getMessage());
            }
        }
    } catch (Exception e) {
        System.out.println(e.getMessage());
    } finally {
        serial.close();
    }

}

Answer 1

You want bytes, but you are reading a string and converting it to bytes. Unfortunately, it looks like in the process your data is getting UTF-8 encoded. For example 0xC3BF is the UTF-8 encoding of "\ÿ" unicode character. Also unfortunately, the only way to get data from SerialDataEvent is as a string. How the original bytes were decoded into a string depend on which string constructor was called. Looks like UTF-16 (probably big endian), so you might try this:

byte[] array = data.getBytes("UTF-16");

This is hacky, the real fix is to improve Pi4J and add a SerialDataEvent.getBytes() method. I hope this works for you.

Answer 2

This worked for me

data.getBytes("ISO-8859-1");

(data.getBytes("UTF-16") was returning 2 bytes per byte read, with 0x00 in the second byte)