Chinese_RFID RC522

AliExpress (also eBay, Amazon) sells many very cheap (under 2$) boards named like "RFID module RC522 Kits S50 13.56 Mhz 6cm With Tags SPI Write & Read for arduno uno 2560".

Some of the boards appears to have a clone chip labeled (in my case)

RC522
12 02
TXD6080
NXP

The chip may also be identified by Version code obtained with reading VersionReg (37h register). The result is 12h

The chip appears to be crippled and not fully functional.

Known flaws

1. VersionReg returns 12h, it's a clone, so ok
2. Self-test returns zeroes
3. Can't change UART speed (SerialSpeedReg)
4. Can't change transmission data rate (TxModeReg) if tag present

See also

1. Review with photos (in Russian)
2. Some logs and stuff