Using MFRC522 with Arduino Pro Mini and ESP-01 in a power save mode. The code is provided as a working example based on the discussion here miguelbalboa/rfid#269

Parts (all none originals from aliexpress):

• MFRC522
• Arduino Pro Mini, 3.5V
• ESP-01 ESP8266

take alook at pinout.txt for the pinout and some ideas behind the project