UKHeliBob:
Yes I am running the code and yes I get "Not allowed!"
That's so damn strange (and frustrating).
UKHeliBob:
Check the 7 connections to the RFID reader very carefully, Which pin on the Arduino does each pin on the reader connect to ?
Yeah, checked that like a hundred times:
Pin 9 - RST
Pin 10 - SDA (same as SS)
Pin 11 - MOSI
Pin 12 - MISO
Pin 13 - SCK
Which means that IRQ is not connected. Furthermore, GND is connected to the ground of Teensy and 3.3V to 3.3V of Teensy. All pins (9 until 13) are digital pins at the Teensy, so that should not be a problem.
The only thing I can imagine is that something is wrong inside the RFID-RC522 reader or Teensy itself, don't you think so? Or is that impossible since I can run codes, like reading the NUID?
(I rebuilt the circuit at another place of my board, because I thought maybe something inside the board could be broken. It had no effect.)