I'm using TTGO ESP32 and I've got an MFRC522 from AliExpress.

I've soldered connector pins to the board itself (both for ESP32 and MFRC522) and I'm using jumper wires female-to-female to connect themselves.

However, using an example sketch (DumpInfo) from miguelbalboa's RFID library, it says communication failure and scanning 3 different key cards or the key fob doesn't output anything.

Firmware Version: 0xFF = (unknown)
WARNING: Communication failure, is the MFRC522 properly connected?

This is my current pinout scheme:

(MFRC - ESP32)
SDA (SS) -> 33
SCK -> 25
MISO -> 27
MOSI -> 26
RST -> 32

And, of course also GND to G and 3.3V to 3.3V.

I've also tried SDA and SCK to connect to 21 and 22, respectively but no luck. Though I have a DS1307 RTC module and microSD card adapter module and connected accordingly and it's working fine, by using Dupont wires, with the same method.

A manufacturer's defect or still I'm making an error somewhere?

You can see TTGO's ESP32 pinout diagram and also a picture of MFRC522 here wired using jumper wires. I may be using (again) the wrong pins. The red LED on the MFRC522 is stable, though.

Thank you in advance.

1 Answer 1


UPDATE! The issue has been fixed, just after finding this stackoverflow answer by bat macumba. I'll leave the question here, in case someone stumbles into the same problem.

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