RC522 Mini Not Work vs RC522 Normal about rfid

[alex-eri]

it works if pulldown RST pin. see #599

[alastaira]

Without seeing the schematic, it sounds like they may have omitted the pullup resistor and/or put an inverter on the RST line. Normally, this pin can be ignored - it's pulled HIGH by default, and you only need write a LOW signal to it to reset the reader. From the description given by @alex-eri , it sounds like you need to do the opposite for this board.

[alex-eri]

[alex-eri]

Not inverted. Pull down needed to make this line of code work
https://github.com/miguelbalboa/rfid/blob/1e73cd34d977c5fe17fa5f2e2e8174650a572028/src/MFRC522.cpp#L210C2-L210C2

else RST pin stays in INPUT mode and FLOATING on many boards ( for example ESP32)

[alex-eri]

pulled HIGH by default only on board without FLOATING input (Arduinos).