PCPL RFID Project

Clone my github repository by executing following commands one by one:

cd ~
git clone https://github.com/arunksoman/PCPL-electro.git
cd PCPL-electro

Following commands are necessary for install Python library used to read RC522 in current working directory:

cd my-project
python setup.py install
cd ..

Run Program

• Rig up the circuit as discussed in class.
• Run the program using main.py using Thonny Python IDE or using python3 main.py from terminal .
• Enter Budget from keypad (In order to verify working of program you have to enter budget between 10,000 and 12,000.
• Read RFID tags (white flat tags) one by one from 1 to 5.

RC 522 Connections

Keypad Connections

• rows = [8, 37, 11, 12]
• cols = [32, 33, 35,36]

Explanation: main.py

Import necessary modules and packages:

import RPi.GPIO as GPIO
import time
import sys
from mfrc522 import SimpleMFRC522

Choosing Physical pin numbering as BOARD and warnings about using GPIO channels are neglected using GPIO.setwarnings.

GPIO.setmode(GPIO.BOARD)
GPIO.setwarnings(False)

Rows of the keypad is connected to GPIO physical pins 8, 37, 11, and 12. While columns are connected to GPIO physical pins ( as per pin BOARD number) 32, 33, 35, and 36.

rows = [8, 37, 11, 12]
cols = [32, 33, 35,36]
keys = [
    ['1', '2', '3', 'A'],
    ['4', '5', '6', 'B'],
    ['7', '8', '9', 'C'],
    ['*', '0', '#', 'D']]

Here I chose a 2D array (Python List) to save name of product, RFID unique number, and price of product respectively.

product = [
    ['Product1', 858624605840, 8000],
    ['Product2', 236811894460, 1000],
    ['Product3', 650705026722, 1200],
    ['Product4', 99658219146, 800],
    ['Product5', 30953647075, 900]
    ]

As I mentioned in the class the GPIO pin connected to row of keypad pulled-low to ground in order to avoid floating condition. GPIO pins connected to column is configured as output.

for row_pin in rows:
    GPIO.setup(row_pin, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

for col_pin in cols:
    GPIO.setup(col_pin, GPIO.OUT)

The keypad is scanned by output a logical HIGH (1) through column pins one by one and scans for 0.3 seconds for key press in order to avoid noise as well as false key press. If there is a short circuit the raw GPIO pin gets a logical HIGH, so that we can detect key press. The following function helps to find out pressed key. Please go through 3 articles I given on readme file.

def get_key():
    key = 0
    for col_num, col_pin in enumerate(cols):
        GPIO.output(col_pin, 1)
        for row_num, row_pin in enumerate(rows):
            if GPIO.input(row_pin):
                key = keys[row_num][col_num]
        GPIO.output(col_pin, 0)
    return key

fixed is a variable that stores maximum digit that can be used for transaction. Here I choose that as 5 so that we can do maximum transaction of ₹99999. count is the variable increments after each detection of each key press. budget, count and fixed are the variables used to convert each digits entered via key press into single number. budget_enter is a boolean variable used as an indicator to identify whether 5 times key press occurred or not.

count = 0
budget = 0
cart = 0
print("Enter your Budget as a 5 digit number on keypad:")
fixed = 5
Budget_enter = False

Next line in the program just calls function within the Python package MFRC522. Please read MFRC522.py within directory MFRC522. This file is core of this project. I didn’t discusses too much about this file due to lack of time. If you want know more download MFRC522 data sheet by NXP (New brand name of well known Philips in chip manufacturing industry). Go to page 36. There NXP discussed about more than 60 registers. Some of them are reserved. But most of them should be edited by using program. Description of these registers extended up to page 69 followed by commands to communicate with MFRC522 to RPi on page 70. This is too much longer so that I didn’t discussed. But you don’t want to bother about that, just scan data sheet provided by manufacture.

reader = SimpleMFRC522()

First line calls function get_key(). If less than 6 key press occurred it converts key press one by one to 5 digit number.

while True:
    key = get_key()
    if count < 6:
        if key :
            print("count = ",count)
            count = count + 1
            temp = int(key) * (10 ** (fixed - count))
            budget = budget + temp
            print("budget = ", budget)

If more than 5 key press occurred warn customer and our indicator variable that indicates whether 5 digit entered or not(Budget_enter) made True.

             if count >= 5:
                Budget_enter = True
                print("You can't enter more than 5 digits")

Only after getting 5 digits(or setting Budget) RFID cards are read.

    if Budget_enter:
        print("Hold a tag near the reader")
        id, text = reader.read() 
        print("ID: ", id)
        print(type(id))

This part of the program comparing RFID unique id stored on 2D list product. If find so, check the second index of 2D array to get prize of product. Add prize on the cart. If added up prize on the cart exceeds give a warning to customer. The program can terminate using keyboard interrupt ctrl+c. While terminating program the program automatically cleans up all last GPIO entries.

         for index in range(5):
            
            if id == product[index][1]:
                prize = product[index][2]
                print(index)
                print("prize = ", prize)
        cart = cart + prize
        print("cart = ", cart)
        if cart > budget:
            print("Warning: Your Budget Exceeded")
    time.sleep(0.3)
GPIO.cleanup()

How to remove a product from cart

In order to add and remove a product from cart one of you said an idea of adding a counter and on even RFID reading product should be added up with cart and on odd RFID reading product should be removed from cart. But in order to do so we want one counter for each card (total 10 counters) also for checking each reading we have to do a modulo division by 2 to find out number of reading is odd or even. My idea to avoid this counter by using a boolean value as an indicator (as we discussed on Budget_enter variable) to each product on the list as shown on example program below. Just copy and paste program given below and run the program on Thonny Python IDE. Choose id1, id2, id3 id4 or id5 on prompt. Observe what happened to list product and cart . Enter same id again and observe the change in product and cart .

#Let a product worth 1300 on cart
cart = 1300
product = [
    ['product1', 'id1', 1200, False],
    ['product2', 'id2', 1300, False],
    ['product3', 'id3', 14000, False],
    ['product4', 'id4', 10000, False], 
    ['product5', 'id5', 1300, False]
    ]

id_select = input("Please Enter any id from id1 to id5: ")

for index in range(5):
	if id_select == product[index][1]:
		print("prize = ", product[index][2])
		if product[index][3] == False:
			product[index][3] = True
			## program to add product to cart
			cart = cart + product[index][2]
			print("Product added to cart =", cart)
print(product)
print("–---------------------------------------------------------------")
id_select = input("Enter same id again: ")
for index in range(5):
	if id_select == product[index][1]:
		print("prize = ", product[index][2])
		if product[index][3] == True:
			product[index][3] = False
			## program to remove product from cart
			cart = cart - product[index][2]
			print("Product removed from cart =", cart)

print(product)