Cyclic Redundancy Check (CRC) Simulator

Anakin B., Ethan W., Sean R.

Usage

The CLI application can be run with:

python crc_cli.py
# Use python3 on Linux

This will start the main menu.

==== MAIN MENU ====
Please enter the menu item number followed by enter (e.g. h).

1 - CRC calculation
2 - CRC validation
3 - Credits
h - Information
q - Quit

The program can be navigated by inputting the character before the -, e.g. 1 and then enter. At anytime, q will return to a previous menu, or exit the program if in the main menu. For convenience, the application will store the last used message/codeword and divisor which can be selected on 0 if available.

For the purposes of demonstrating the calculation of a CRC, each step of the calculation is shown and laid out in the terminal as you would do by hand.

For example with the message 1010011 and:

Divisor:    CRC-8
Binary:     111010101
Polynomial: x^8 + x^7 + x^6 + x^4 + x^2 + 1

We get:

Calculating CRC code:
101001100000000
111010101       XOR
---------
0100110010
 111010101      XOR
 ---------
 0111001110
  111010101     XOR
  ---------
  0000110110000
      111010101 XOR
      ---------
      001100101 Done

CRC Code:        01100101
Codeword: 101001101100101

A similar process will occur for validation, however, the program will look for a division remainder of 0 to signify that the data contains no detectable errors.

CRC Standards

The application allows the user to select a CRC standard to use as the divisor. The standards currently programmed in are:

1. CRC-16
2. CRC-16-CCITT
3. CRC-12
4. CRC-32
5. CRC-8
6. CRC-1 (Parity bit)

The user may also enter their own CRC if they so wish.

Application Flow

The sub-routines Calculate CRC and Validate CRC follow a general flow from routine to calculation as such:

flowchart TD
    main(CLI Main Menu)
    calc_crc_routine[[Calculate CRC]]
    val_crc_routine[[Validate CRC]]

    
    
    subgraph Main
        main --> calc_crc_routine
        main --> val_crc_routine
        calc_crc_routine --> Routines
        val_crc_routine --> Routines
    end

    subgraph Routines
        routine(Routine)
        msg_menu[Message Menu]
        msg_handler[Message Handler]
        crc_menu[CRC Menu]
        crc_handler[CRC Handler]
        calculation[[CRC Calculation]]
        
        routine --> msg_menu
        msg_menu --> msg_handler
        msg_handler --> crc_menu

        crc_menu --> crc_handler
        
        crc_handler --> calculation
    end
    

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