How to fix uid in NFC

Question

I want to fix uid for nexus s and when use the phone to tag at NFC shield. The shield will show id. But when it tag at the nfc shield, id is not same. Can I fix my uid ?

Answer 1

What you likely see is the NFCID: the NFC peer-to-peer ID. This ID is randomly generated anew by the NFC hardware on every NFC connection and cannot be fixed.

Answer 2

当前的SDK不允许您使用卡片仿真，因此您无法将手机用作标签。

Answer 3

Because the ID changes for the peer-to-peer on every connection, you'll have to define an NDEF record with a text value in it. Make that value your fixed ID. On the other side, on the shield, you'll need to read out that record to find your fixed value/ID.

https://github.com/adafruit/Adafruit_NFCShield_I2C/tree/master/examples has some examples on how to manipulate NDEF records but only on MiFare classics. If you're using Ultralights or other kinds of tags, this will be different.