I am trying to run this code: https://github.com/miguelbalboa/rfid/blob/master/examples/ReadNUID/ReadNUID.ino

Using an ESP8266 based D1 board and an RFID-RC522.

I am not able to get it to detect the rfid tags ...
the serial monitor just shows:

 ets Jan  8 2013,rst cause:4, boot mode:(3,4)

wdt reset
load 0x4010f000, len 1384, room 16 
tail 8
chksum 0x2d
csum 0x2d

The "Typical pin layout used" section of the above document does not mention any connections on the 3.3V & GND pins of the RFID-RC522 card.

Does this mean that I do not need to connect them?
Or is is just so obvious that I should connect them that they did not bother to write it in that section?

  • Where is this "written down" that you are talking about? Commented Jul 31, 2016 at 21:26
  • in the "Typical pin layout" section of the document I mentioned above.
    – epeleg
    Commented Aug 1, 2016 at 7:14
  • Stupid question, but apart from connecting the power, have you uploaded the code? Commented Aug 1, 2016 at 7:46

1 Answer 1


It is just so obvious that you should connect them that they did not bother to write it down.

The reader needs power. That is taken as read. Without power it can do nothing. Why would they bother to waste time telling you to connect the things that you have to connect regardless? The only things that they tell you to connect are things that are specific to the sketch - i.e., which IO pins to connect to which function on the reader. Power doesn't change - it's the same from sketch to sketch and from person to person. The IO pins do, though, and need to be detailed. Power and ground don't.

  • o.k. thanks. Its the first time I try to connect anything to my arduino... wat about an IRQ pin on the RC522? is this another standard pin I should know about? or does it just remain un connected?
    – epeleg
    Commented Aug 1, 2016 at 7:18
  • @epeleg You said you were using a D1. Commented Aug 1, 2016 at 7:45
  • Sorry, your are right of course.It is indeed a D1 board. being new to this area I still think of all those boards as "arduinos" but I now start to understand that this is not the case and each board is different. So to be more precise I am using a an ESP8266 based D1. and I think its considered a "retired" board as it turns out that there are newer releases of it (R2). That said, I do own also an "adeept" uno - is this considered an arduino? or arduino compatible board?
    – epeleg
    Commented Aug 1, 2016 at 19:38
  • Even after connecting the 3.3V and GND wires I still cant get the RFID-RC522 to detect neither the plastic nor pvc tag. I wander if I will have better luck if I use the "adeept" Uno... because I realy don't know why it does not work... maybe i need to initialize the tags somehow?
    – epeleg
    Commented Aug 1, 2016 at 19:39
  • just to add - I do manage to send a program to the D1 board and for example blink its onboard led.
    – epeleg
    Commented Aug 1, 2016 at 19:39

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