Use RFID reader AND a 4x4 matrix keypad with breadboard

Question

I am trying to set up a pi to use rfid to scan a card and if the card is correct, the user will enter in a 4 digit code into a 4x4 matrix keypad. Each device works perfectly fine independently however if I connect both using a breadboard, it works once but requires a reboot to work again. Below is the code I'm using to get this to work. I read that I may need to use different spi pins but I'm not sure how. I'm a beginner at best. Any help would be greatly appreciated. Thank you!

#!/usr/bin/env python
# -*- coding: utf8 -*-
import RPi.GPIO as GPIO
import MFRC522
import time
import signal
import os

continue_reading = True

# Capture SIGINT for cleanup when the script is aborted
def end_read(signal,frame):
global continue_reading
print "Ctrl+C captured, ending read."
continue_reading = False
GPIO.cleanup()

# Hook the SIGINT
signal.signal(signal.SIGINT, end_read)

# Create an object of the class MFRC522
MIFAREReader = MFRC522.MFRC522()

# Welcome message
print "Welcome to the MFRC522 data read example"
print "Press Ctrl-C to stop."

# This loop keeps checking for chips. If one is near it will get the UID 
and authenticate
while continue_reading:

# Scan for cards    
(status,TagType) = MIFAREReader.MFRC522_Request(MIFAREReader.PICC_REQIDL)

# If a card is found
if status == MIFAREReader.MI_OK:
    print "Card detected"

# Get the UID of the card
(status,uid) = MIFAREReader.MFRC522_Anticoll()

# If we have the UID, continue
if status == MIFAREReader.MI_OK:

    # Print UID
    #print "Card read UID: "+str(uid[0])+","+str(uid[1])+","+str(uid[2])+","+str(uid[3])
    print "Card read UID: {0}, {1}, {2}, {3}".format(*uid)

    if uid[:4] == [68, 193, 21, 186]:
        print "Access Granted"

        #os.system('mpg123 -q resources/Access_Granted.mp3 &')

        #time.sleep(5)

        #os.system('pkill -9 mpg123')

        continue_reading = False
        opendoor = "147*"
        closedoor = "369#"
        keypress = ""

        MATRIX = [ [1,2,3,'A'],
                   [4,5,6,'B'],
                   [7,8,9,'C'],
                   ['*',0,'#','D'] ]

        ROW = [3,5,8,10]
        COL = [19,21,23,24]

        for j in range(4):
            GPIO.setup(COL[j], GPIO.OUT)
            GPIO.output(COL[j],1)

        for i in range(4):
            GPIO.setup(ROW[i], GPIO.IN, pull_up_down = GPIO.PUD_UP)

        try:
            while(True):
                for j in range(4):
                    GPIO.output(COL[j],0)

                    for i in range(4):
                        if GPIO.input(ROW[i]) == 0:
                            print (MATRIX[i][j])
                            keypress = keypress + str(MATRIX[i][j])
                            if len(keypress) == 4:
                                if keypress == opendoor:

                                    print("open door")
                                    os.system('mpg123 -q resources/Access_Granted.mp3 &')

                                    time.sleep(3)

                                    os.system('pkill -9 mpg123')

                                    GPIO.setup(18, GPIO.OUT)
                                    GPIO.output(18, GPIO.LOW)
                                    keypress = ""
                                elif keypress == closedoor:
                                    print("close door")
                                    GPIO.setup(18, GPIO.OUT)
                                    GPIO.output(18, GPIO.HIGH)
                                    keypress = ""
                                else:
                                    print("wrong code")
                                    keypress = ""
                            time.sleep(0.2)
                            while(GPIO.input(ROW[i]) == 0):
                                pass

                    GPIO.output(COL[j],1)
        finally:
            print ""
    else:
        print "Acess Denied"

    # This is the default key for authentication
    #key = [0xFF,0xFF,0xFF,0xFF,0xFF,0xFF]

    # Select the scanned tag
    #MIFAREReader.MFRC522_SelectTag(uid)

    # Authenticate
    #status = MIFAREReader.MFRC522_Auth(MIFAREReader.PICC_AUTHENT1A, 8, key, uid)

    # Check if authenticated
    #if status == MIFAREReader.MI_OK:
        #MIFAREReader.MFRC522_Read(8)
        #MIFAREReader.MFRC522_StopCrypto1()
    #else:
        #print "Authentication error"

Answer 1

The code is not formatted properly so I did not try to run the script.

Are you sure you copied the code properly? I would expect to see a set up of the GPIO numbering system to be used, i.e. GPIO.setmode(GPIO.BOARD) or GPIO.setmode(GPIO.BCM).

Neither is it clear which SPI channel you are using as this is concealed within the MFRC522 class.

For the sake of answering your question I will use Broadcom GPIO numbering (BCM in RPi.GPIO code).

I will also assume you are using SPI channel 0.

SPI channel 0 uses (Broadcom) GPIO 8, 9, 10, and 11. Make sure you do not use any of these GPIO for your keyboard matrix.

See https://pinout.xyz/