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.. _3.1.8_c:

3.1.8 Password Lock
======================================

Introduction
-------------

In this project, we will use a keypad and a LCD to make a combination
lock. The LCD will display a corresponding prompt for you to type your
password on the Keypad. If the password is input correctly, “Correct”
will be displayed.

On the basis of this project, we can add additional electronic
components, such as buzzer, LED and so on, to add different experimental
phenomena for password input.

Required Components
------------------------------

In this project, we need the following components.

.. image:: ../img/list_Password_Lock.png
    :align: center

It's definitely convenient to buy a whole kit, here's the link: 

.. list-table::
    :widths: 20 20 20
    :header-rows: 1

    *   - Name	
        - ITEMS IN THIS KIT
        - LINK
    *   - Raphael Kit
        - 337
        - |link_Raphael_kit|

You can also buy them separately from the links below.

.. list-table::
    :widths: 30 20
    :header-rows: 1

    *   - COMPONENT INTRODUCTION
        - PURCHASE LINK

    *   - :ref:`cpn_gpio_board`
        - |link_gpio_board_buy|
    *   - :ref:`cpn_breadboard`
        - |link_breadboard_buy|
    *   - :ref:`cpn_wires`
        - |link_wires_buy|
    *   - :ref:`cpn_resistor`
        - |link_resistor_buy|
    *   - :ref:`cpn_i2c_lcd`
        - |link_i2clcd1602_buy|
    *   - :ref:`cpn_keypad`
        - \-

Schematic Diagram
------------------

============ ======== ======== ===
T-Board Name physical wiringPi BCM
GPIO18       Pin 12   1        18
GPIO23       Pin 16   4        23
GPIO24       Pin 18   5        24
GPIO25       Pin 22   6        25
GPIO17       Pin 11   0        17
GPIO27       Pin 13   2        27
GPIO22       Pin 15   3        22
SPIMOSI      Pin 19   12       10
SDA1         Pin 3             
SCL1         Pin 5             
============ ======== ======== ===

.. image:: ../img/Schematic_three_one9.png
   :align: center

Experimental Procedures
-------------------------

**Step 1:** Build the circuit.

.. image:: ../img/image262.png

**Step 2**: Change directory.

.. raw:: html

   <run></run>

.. code-block:: 

    cd ~/raphael-kit/c/3.1.8/

**Step 3**: Compile.

.. raw:: html

   <run></run>

.. code-block::

    gcc 3.1.8_PasswordLock.cpp -lwiringPi

**Step 4:** Run.

.. raw:: html

   <run></run>

.. code-block::

    sudo ./a.out

After the code runs, use the keypad to enter the correct password: 1984. If the “CORRECT”
appears on LCD1602, there is no wrong with the password; otherwise,
“WRONG KEY” will appear.

.. note::

    * If there is an error prompt ``wiringPi.h: No such file or directory``, please refer to :ref:`install_wiringpi`.
    * If you get ``Unable to open I2C device: No such file or directory`` error, you need to refer to :ref:`i2c_config` to enable I2C and check if the wiring is correct.
    * If the code and wiring are fine, but the LCD still does not display content, you can turn the potentiometer on the back to increase the contrast.

**Code Explanation**

.. code-block:: c

    #define ROWS  4 
    #define COLS  4
    #define BUTTON_NUM (ROWS * COLS)
    #define LENS  4

    unsigned char KEYS[BUTTON_NUM] {  
    '1','2','3','A',
    '4','5','6','B',
    '7','8','9','C',
    '*','0','#','D'};

    char password[LENS]={'1','9','8','4'};

Here, we define the length of the password LENS, storage matrix keyboard
key value array KEYS and the array that stores the correct password.

.. code-block:: c

    void keyRead(unsigned char* result);
    bool keyCompare(unsigned char* a, unsigned char* b);
    void keyCopy(unsigned char* a, unsigned char* b);
    void keyPrint(unsigned char* a);
    void keyClear(unsigned char* a);
    int keyIndexOf(const char value);

There is a declaration of the subfunctions of the matrix keyboard code,
refer to :ref:`2.1.8_c` of this document for more details.

.. code-block:: c

    void write_word(int data);
    void send_command(int comm);
    void send_data(int data);
    void lcdInit();
    void clear();
    void write(int x, int y, char const data[]);

There is a declaration of the subfunctions of LCD1062 code, refer to :ref:`1.1.7_c` of this document for more details.

.. code-block:: c

    while(1){
            keyRead(pressed_keys);
            bool comp = keyCompare(pressed_keys, last_key_pressed);
            ...
                    testword[keyIndex]=pressed_keys[0];
                    keyIndex++;
                    if(keyIndex==LENS){
                        if(check()==0){
                            clear();
                            write(3, 0, "WRONG KEY!");
                            write(0, 1, "please try again");
                            }
                    ...

Read the key value and store it in the test array testword. If the
number of stored key values is more than 4, the correctness of the
password is automatically verified, and the verification results are
displayed on the LCD interface.

.. code-block:: c

    int check(){
        for(int i=0;i<LENS;i++){
            if(password[i]!=testword[i])
            {return 0;}
        }
        return 1;
    }


Verify the correctness of the password. Return 1 if the password is
entered correctly, and 0 if not.

Phenomenon Picture
---------------------

.. image:: ../img/image263.jpeg
   :align: center