Arduino Lesson 12 : Arduino UNO with 4*4 Keypad and 16*2 LCD

Intro to topic :

Keyboard or in this case keypad is very essential for many types of user data entry like passwords,number, or data integers so it is important to know about interfacing of keypad with arduino and manipulating it. Here i am discussing that how to interface keypad with arduino UNO.
Some time we needed that data we are entering should be shown to some sort of display or screen we used LCD to display the data entered.

Hardware required :

1. Arduino UNO board.
2. Hex keypad 4*4
3. Connecting wires/Jumper wires.
4. PC to configure arduino board (with arduino software installed).
5. Bread board.

 

Steps to follow :

1. Connect the Keypad and LCD according to image.
2. Use equal length jumper wires for ease.
3. After this connect the board to PC by USB cable and then open up the IDE in PC
4. Then upload the following Code.

Code to be uploaded :

#include<LiquidCrystal.h>  
LiquidCrystal lcd(7,6,5,4,3,2); 
int row[]={A1,A0,8,9};// Defining row pins of keypad connected to Arduino pins
int col[]={10,11,12,13};//Defining column pins of keypad connected to Arduino
int i,j,lcd_count,count=1,key_id=0,flag,entry=0;// See About the Program 
int col_scan;// Variable to identify a key press
char temp_press; // Variable to hold value of key press
char check[6],pass[6]; // See About the Program

void setup()
{
lcd.begin(16,2);
for(i=0;i<=3;i++)
{
pinMode(row[i],OUTPUT);
pinMode(col[i],INPUT);
digitalWrite(col[i],HIGH);
}
lcd.print("SET 5 Digit PASS");
}

/* Main Program Begins */

void loop()
{ 
 while(entry<=4)// Password Setting Loop begins
{
SetPassword();
}
// Password Setting Loop Ends

key_id=0;
keyscan(); // Scan for a Key Press

/* Actions on Key Press begins */

if(key_id==1) // Condition to Check Key is Pressed
{
 check[count]=temp_press;
count++;

/* Condition to Unlock Begins*/

if(temp_press=='A')
{
  checkPassword();
if(flag==0)
{
lcd.setCursor(0,0);
lcd.print("UNLOCKED");

}else{ 
lcd.setCursor(0,0);
lcd.print("WRONG PASSWORD");
delay(200);
lcd.clear();
lcd.print("LOCKED");
}
count=1; // Resetting the counter variable
}

/* Condition to Unlock Ends*/

/* Condition to Change Password Begins */

else if(temp_press=='C')
{
checkPassword();
if(flag==0)
{
lcd.setCursor(0,0);
lcd.print("ENTER NEW PASS");
key_id=0;
entry=0;
}else{ 
lcd.setCursor(0,0);
lcd.print("WRONG PASSWORD");
}
count=1; // Resetting the counter variable
}

/* Condition to Change Password Ends */

/* Condition to LOCK Begins*/

else if(temp_press=='B')
{
lcd.setCursor(0,0);
lcd.print("LOCKED");
count=1; // Resetting the counter variable
}
/* Condition to LOCK Ends*/
}

/* Actions on Key Press Ends*/
}

/* Main Program Ends */


void SetPassword() // Subroutine to SET User Defined Password
{
keyscan();
if(key_id==1)
{
if(temp_press=='A'||temp_press=='C'||temp_press=='B') // Condition to Check for an Invalid Keypress 
{
lcd.setCursor(0,0);
lcd.print("INVALID KEYS");
entry=0;
}
else 

{
  pass[entry]=temp_press;

}
}
key_id=0;
if(entry==5)
{
lcd.clear();
lcd.setCursor(0,0);
lcd.print("PASSWORD SET & LOCKED");
}} // Subroutine to SET Password ENDS

char keyscan()// Subroutine to Scan Keypad for a Keypress
{
for(i=0; i<=3; i++)
{
digitalWrite(row[0],HIGH);
digitalWrite(row[1],HIGH);
digitalWrite(row[2],HIGH);
digitalWrite(row[3],HIGH);
digitalWrite(row[i],LOW);
for(j=0; j<=3; j++)
{
col_scan=digitalRead(col[j]);
if(col_scan==LOW)
{
  key_id=1;
  entry++;
temp_press=keypress(i,j);
lcd.setCursor(lcd_count++,1);
lcd.print(temp_press);
if(temp_press=='A'||temp_press=='C'||temp_press=='B')
{
lcd_count=0;
lcd.clear();
}
delay(300);
break;
}}
}}// Subroutine to Scan Keypress Ends

char keypress(int i, int j) // Subroutine to Identify the value of Key pressed
{
if(i==0&&j==0)
{
return('1');
}
if(i==0&&j==1)
{
return('2');
}
if(i==0&&j==2)
{
return('3');
}
if(i==0&&j==3)
{
return('A');
}
if(i==1&&j==0)
{
return('4');
}
if(i==1&&j==1)
{
return('5');
}
if(i==1&&j==2)
{
return('6');
}
if(i==1&&j==3)
{
return('B');
}
if(i==2&&j==0)
{
return('7');
}
if(i==2&&j==1)
{
return('8');
}
if(i==2&&j==2)
{
return('9');
}
if(i==2&&j==3)
{
return('C');
}
if(i==3&&j==0)
{
return('*');
}
if(i==3&&j==1)
{
return('0');
}
if(i==3&&j==2)
{
return('#');
}
if(i==3&&j==3)
{
return('D');
}
} // Subroutine to identify Keypress Ends

void checkPassword() // Subroutine to Check User Input Data with SET Password
{
flag=0;
for(i=1;i<=5&&flag==0;i++)
{
if(check[i]==pass[i])
{
flag=0;
}
else 
{flag=1;
}}} // Subroutine to check password ends

                                

Once the code is uploaded you can follow up the screen and any time you input correct code the pin will be unlocked