How to integrate an RFID module with Raspberry Pi

Published by DevicePlus Editorial Team at June 30, 2021

Purpose

The purpose of this tutorial is show how to integrate an RFID reader and an actuator with a Raspberry Pi. The basic principles discussed lay the foundation to make an RFID doggy door.

Overview

In this tutorial, I go over how to integrate the RC522 RFID module with a Raspberry Pi board. I also show how to integrate an actuator, in this case an LED, to respond to a correct reading from the RFID module. This actuator can be a solenoid lock, a speaker, or even a web interface that logs data. I discuss how this design can be implemented as an RFID doggy door.

Equipment

Table 1: Equipment

Item	Link
Raspberry Pi 3	Link for Raspberry Pi
RC522 RFID Module	Link for RFID Module
HDMI Cable	Link for HDMI Cable
LED	Link for LEDs from Adafruit
Mouse + Keyboard	Amazon Link for Keyboard/Mouse
Monitor/TV	Any TV or monitor with HDMI
Jumper Wires	Amazon Link for Jumper Wires
Micro USB Cable	Amazon Link for Micro USB Cable
Breadboard	Amazon Link for Breadboard

Step-by-Step Guide to Integrating an RFID Module with Raspberry Pi

1. Designing the Circuit

I always like to make a wiring diagram (Figure 1: Circuit Schematic w/ LED) using Fritzing, an open-sources schematic capture and PCB routing software. You can download Fritzing using the following link (optional): http://fritzing.org/home/

The first schematic is of the circuit I am building with an LED as an actuator. The LED will turn on when a correct reading is made by the RFID module.

The second circuit is with a solenoid as an actuator. This is the circuit you want to implement the design as a door lock or a doggy door. The TIP120 is a Darlington Array power transistor. This simply allows the Raspberry Pi to control the solenoid, which requires more power than the Raspberry Pi’s GPIO can output.

Figure 1: Circuit Schematic w/ LED

Figure 2: Circuit Schematic w/ SolenoidThe RC522 RFID module uses SPI (Serial Peripheral Interface Bus) to interface to the Raspberry Pi. SPI is a fairly common bus used in embedded systems. The reader should be wired according the table below.

Table 2: RC522 Wiring Table

RC522 Pin	Raspberry Pi Pin	Wire Color
3.3V	Pin 1	Red
RST	Pin 22	Orange
GND	Pin 6	Black
MISO	Pin 21	White
MOSI	Pin 19	Grey
SCK	Pin 23	Green
SDA	Pin 24	Blue

I’ve connected my actuator (an LED) to Pin 18 on the Raspberry Pi. This is the pin that you should connect

2. Writing the Code

a. Enabling SPI

The first step is to enable SPI on the Raspberry Pi. To do this, open a command line window and enter sudo raspi-config. This will open the Configuration Menu. Select menu 5 “Interfacing Options.” Now select “P4 SPI.” When asked if you want to enable the SPI Interface, select yes. The configuration menu will say “The SPI interface is enabled.” To finish enabling SPI, open a command line terminal and enter the command sudo reboot. This will reboot the Raspberry Pi can finish enabling SPI.

b. Installing Packages
The libraries we will use are written in Python 2, not Python 3. So the first step is to install Python 2.7. This is done by entering sudo apt-get install python2.7-dev. The SPI PY library is used interface with the RC522 module. I clone the library by typing the command git clone https://github.com/lthiery/SPI-Py.git. The library then needs to be installed. First, enter the SPI-Py directory by typing cd SPI-Py. Then install the library, sudo python setup.py install.

c. Adding to Read.py
Read.py is the script you need to change to talk to the RC522 module. While editing this script, scroll to the bottom of the script and comment out “Authenticate.” This tutorial doesn’t cover RFID authentication. Be sure to import time library at the header of the script. Next find the section with the heading “#Configure LED Output Pin.” This is where you should configure your actuator. If you are implementing this design as a doggy door, configure the output pins to the solenoids.

Next go to the heading “#Check to see if card UID read matches your card UID.” This If/Else statement checks the UID the reader reads from a card to a UID you have saved in the script. If the UIDs match, the actuator is outputted to a HIGH.

3. Running the Code

a. Getting the UID

The first time running the script you need to get your card’s UID. An RFID card UID is a unique number associated with the card, similar to a serial number.

To run the script, change directories to the directory you’ve saved the script in. Run the script by typing python Read.py. Because the script has my card’s UID on it, when you place your card up to the reader it will deny access. The card’s UID will be displayed on the screen. Note the UID. Edit the script and change the script’s UID to this value and save it.

Figure 3: Script Running w/ UID Printing

Figure 3: Script Running w/ UID Printingb. Running the Final Script

Run the script again by typing python Read.py. Now when you place your card to the reader, access should be granted and the LED will turn on for 5 seconds. If you have implemented your design as a doggy door, the solenoid should open when access is granted.

Figure 4: Waiting to Read Card

Figure 5: Access Granted4. Considerations if Implementing as a Doggy Door

1. Add a second solenoid to lock the door from both sides.
2. Add a hall effect (Magnetic Sensor) sensor and a magnet to the door so the Raspberry Pi knows the door has returned to the closed position before locking it.
3. If you are really ambitious you can design your own large loop antenna around the door instead of mounting the small reader to the door. You will need magnet wire, and will need to solder to connect to the reader module. This will require advanced skill. You can read about loop antennas here.
4. If you are an advanced programmer, you can read the MFRC522 datasheet and change the firmware on the chipset to better meet your application.

5. Other Implementations

1. A door lock
2. A safe lock
3. Fare Payment Devices
4. Transportation Tracking/Logistics
5. Retail/Shopping

6. Appendix: Read.py

#!/usr/bin/env python
# -*- coding: utf8 -*-
 
import RPi.GPIO as GPIO
import MFRC522
import signal
import time
 
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])+','+str(uid[4]))  
        # This is the default key for authentication
        key = [0xFF,0xFF,0xFF,0xFF,0xFF,0xFF]
        
        # Select the scanned tag
        MIFAREReader.MFRC522_SelectTag(uid)
        
        #ENTER Your Card UID here
        my_uid = [61,84,4,114,31]
        
        #Configure LED Output Pin
        LED = 18
        GPIO.setup(LED, GPIO.OUT)
        GPIO.output(LED, GPIO.LOW)
        
        #Check to see if card UID read matches your card UID
        if uid == my_uid:                #Open the Doggy Door if matching UIDs
            print("Access Granted")
            GPIO.output(LED, GPIO.HIGH)  #Turn on LED
            time.sleep(5)                #Wait 5 Seconds
            GPIO.output(LED, GPIO.LOW)   #Turn off LED
            
        else:                            #Don't open if UIDs don't match
            print("Access Denied, YOU SHALL NOT PASS!")
        
##        # 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"

#!/usr/bin/env python

# -*- coding: utf8 -*-

import RPi.GPIO as GPIO

import MFRC522

import signal

import time

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])+','+str(uid[4]))

# This is the default key for authentication

key = [0xFF,0xFF,0xFF,0xFF,0xFF,0xFF]

# Select the scanned tag

MIFAREReader.MFRC522_SelectTag(uid)

#ENTER Your Card UID here

my_uid = [61,84,4,114,31]

#Configure LED Output Pin

LED = 18

GPIO.setup(LED, GPIO.OUT)

GPIO.output(LED, GPIO.LOW)

#Check to see if card UID read matches your card UID

if uid == my_uid: #Open the Doggy Door if matching UIDs

print("Access Granted")

GPIO.output(LED, GPIO.HIGH) #Turn on LED

time.sleep(5) #Wait 5 Seconds

GPIO.output(LED, GPIO.LOW) #Turn off LED

else: #Don't open if UIDs don't match

print("Access Denied, YOU SHALL NOT PASS!")

## # 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"

If you’re interested in learning a little more about Raspberry Pi, why not check out some of our other great articles?

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How to integrate an RFID module with Raspberry Pi

Table of Contents

Purpose

Overview

Equipment

Step-by-Step Guide to Integrating an RFID Module with Raspberry Pi

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