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uniquenfcuniqueidentifierreader

nativescript-nfc rfid reader plugin unique id issue

I use the nfc reader and Im able to get the unique id of the tags. When I read the tag the id is called like this:

id: [ -52, 22, -61, -67, 80, 1, 4, -32, [length]: 8 ]

How can I get the hexadecimal one? It should be called CC:16:C3:BD:50:01:04:E0. That's also the way I will have database entries. So the way I get the id back is somehow useless for me.

I will appreciate any helpful answer. Thank you in advance.

Solution

  • The range of byte is -128 to 127

    e.g. For Java https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

    "byte: The byte data type is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive)."

    You just need to convert that to display as a String as Hex.

    Usually According to ISO/IEC 14443-3 the UID is a 7 byte Number with byte 4 being part of the check bytes

    I don't know how to convert bytes to string in Nativescript but in Java you can do

    
StringBuilder Uid = new StringBuilder();

for (int i = 0; i < result.length; i++) {
                        // byte 4 is a check byte
                        if (i == 3) continue;
                        Uid.append(String.format("%02X ", result[i]));
                    }

    While skipping the check byte is not totally needed to give you an unique ID this code does it.

    For JavaScript How to convert hex string into a bytes array, and a bytes array in the hex string? should provide the answer with a similar iterate over the array converting each byte to hex string