Will the address of MFRC630 NFC card reader change when using I2C communication?

[chcmq]

Sometimes it is 0x2A, and sometimes it is 0x2B, which will cause me to fail when initializing the card reader. How can I keep it unchanged?

[iwanders]

Hmm, check the datasheet on page 22, section 8.4.4.6. It is most likely that your ADR1 or ADR2 pin is floating and switching by accident. Check section 8.4.1, table 7, give pin 28 and 31 either a pull up or a pull down, that should ensure their state doesn't change and the address stays stable.