CODEWITHSUNDEEP
pythonraspberry-pirfidmifare
user3194279
user3194279

Reputation: 31

How to read 7 bytes long Desfire uid using rc522 and Raspberry Pi?

I use this library https://github.com/mxgxw/MFRC522-python to read UID using rc522 reader and Raspberry Pi. It works great for cards with 4 bytes long uid but I am unable to read 7 bytes long Desfire uid. I read that it is necessary to edit anti collision algorithm when cascade bit is 1. How to modify this library to be able to read 7 bytes long uid ?

Upvotes: 3

Views: 2341

Answers (1)

Sergio Ferrer Sánchez
Sergio Ferrer Sánchez

Reputation: 310

I have just come here with the same problem. Although more than 4 years have passed, maybe my solution can help someone.

1) Rename (or delete) the current MFRC522-python library

cd ~/.local/lib/python2.7  # or your python version
mv pirc522 pirc522_original

2) Create a new directory (if it does not exists) for the installation of a new library

mkdir /usr/local/lib/python2.7/dist-packages  # or your python version

3) Install this other version of the library, which contains a function anticoll2() that allows you to read more bytes from the RFID Card

git clone https://github.com/ondryaso/pi-rc522.git
cd pi-rc522
python setup.py install

And that's all. You can import this new library the same way you imported the previous one.

Now, to read a RFID card, remember that a 7-bytes RFID card starts with 0x88. So you can use the new function anticoll2() in this library to read more data when anticoll() returns 0x88 on the first position. Here's is an example:

from pirc522 import RFID

def detect_uid(reader):
    (error, tag_type) = reader.request()
    (error, uid) = reader.anticoll()

    if uid[0] != 0x88:
        rfid_uid = uid[0:4]  # classic 4bytes-rfid card
    else:
        (error, uid2) = reader.anticoll2()
        rfid_uid = uid[1:4] + uid2[:4]  # 7bytes-rfid card

    return rfid_uid


reader = pirc522.RFID()
print("UID: " + str(detect_uid(reader)))

Upvotes: 1

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