Connect 2 RC522 to Raspberry Pi

Question

I wanted to connect 2 RC522 to my Raspberry Pi. I Followed the instructions from here. But then I got the error message:

/usr/local/lib/python3.9/dist-packages/mfrc522/MFRC522.py:151: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
  GPIO.setup(pin_rst, GPIO.OUT)
Traceback (most recent call last):
  File "/home/pi/Desktop/rfid.py", line 63, in <module>
    data = nfc.read("reader1")
  File "/home/pi/Desktop/rfid.py", line 39, in read
    if not self.selectBoard(rid):
  File "/home/pi/Desktop/rfid.py", line 35, in selectBoard
    GPIO.output(self.boards[loop_id], loop_id == rid)
RuntimeError: The GPIO channel has not been set up as an OUTPUT

Can someone help me what I am doing wrong?

Answer 1

after a long search I found a working answer for the error: "RuntimeError: The GPIO channel has not been set up as an OUTPUT":

The problem really is as it says. The used GPIO Pins (here 5 and 6) are not set as an output. To do that at the beginnig of the script you have to add:

GPIO.setmode(GPIO.BCM)               
GPIO.setup(5, GPIO.OUT)
GPIO.setup(6, GPIO.OUT)

So the whole script would look like(for two RC522 readers):

import RPi.GPIO as GPIO
from mfrc522 import SimpleMFRC522
import spidev

GPIO.setmode(GPIO.BCM)               
GPIO.setup(5, GPIO.OUT)
GPIO.setup(6, GPIO.OUT)

class NFC():
    def __init__(self, bus=0, device=0, spd=1000000):
        self.reader = SimpleMFRC522()
        self.close()
        self.bus
        self.boards = {}
        
        self.bus = bus
        self.device = device
        self.spd = spd

    def reinit(self):
        self.reader.READER.spi = spidev.SpiDev()
        self.reader.READER.spi.open(self.bus, self.device)
        self.reader.READER.spi.max_speed_hz = self.spd
        self.reader.READER.MFRC522_Init()

    def close(self):
        self.reader.READER.spi.close()

    def addBoard(self, rid, pin):
        self.boards[rid] = pin

    def selectBoard(self, rid):
        if not rid in self.boards:
            print("readerid " + rid + " not found")
            return False

        for loop_id in self.boards:
            GPIO.output(self.boards[loop_id], loop_id == rid)
        return True

    def read(self, rid):
        if not self.selectBoard(rid):
            return None

        self.reinit()
        cid, val = self.reader.read_no_block()
        self.close()

        return val

    def write(self, rid, value):
        if not self.selectBoard(rid):
            return False

        self.reinit()
        self.reader.write_no_block(value)
        self.close()
        return True


if __name__ == "__main__":
    nfc = NFC()
    nfc.addBoard("reader1",5)
    nfc.addBoard("reader2",6)

    data = nfc.read("reader1")
    nfc.write("reader2",data)

I hope this will help others :)