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.

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

../_images/Schematic_three_one9.png

Experimental Procedures

Step 1: Build the circuit.

../_images/image262.png

Step 2: Change directory.

cd /home/pi/raphael-kit/c/3.1.8/

Step 3: Compile.

gcc 3.1.8_PasswordLock.cpp -lwiringPi

Step 4: Run.

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 it does not work after running, or there is an error prompt: “wiringPi.h: No such file or directory”, please refer to C code is not working?.

Code Explanation

#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.

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 2.1.8 Keypad of this document for more details.

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 1.1.7 I2C LCD1602 of this document for more details.

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.

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

../_images/image263.jpeg