#include <LiquidCrystal.h>
LiquidCrystal lcd(18,5,17,16,4,0);
const int keyPadRow[4]={12,14,27,26};
const int keyPadCol[4]={25,33,32,13};

void setup() {
  // put your setup code here, to run once:
  lcd.begin(16,2);
  lcd.print("keypad program");
  delay(1000);
}

void loop() {
  // put your main code here, to run repeatedly:
 getkey();
 delay(100);
}
void getkey(void){
  int row=-1,col=-1;
  for(int i=0;i<4;i++){
    pinMode(keyPadRow[i], INPUT_PULLUP);
    pinMode(keyPadCol[i], OUTPUT);
    digitalWrite(keyPadCol[i], LOW);
  }
  for(int i=0;i<4;i++){
    if(digitalRead(keyPadRow[i])==0){
      row=i;
    }
  }
  if(row!=-1){
    for(int i=0;i<4;i++){
      pinMode(keyPadCol[i], INPUT_PULLUP);
      pinMode(keyPadRow[i], OUTPUT);
      digitalWrite(keyPadRow[i], LOW);
    }
    for(int i=0;i<4;i++){
      if(digitalRead(keyPadCol[i])==0){
        col=i;
      }
    }
    if(col!=-1){
      if(row==0){
        if(col==0){
        lcd_display_num('1');
      }
      else if(col==1){
        lcd_display_num('2');
      }
      else if(col==2){
        lcd_display_num('3');
      }
      else if(col==3){
        lcd_display_num('A');
      }
    }
     if(row==1){
        if(col==0){
        lcd_display_num('4');
      }
      else if(col==1){
        lcd_display_num('5');
      }
      else if(col==2){
        lcd_display_num('6');
      }
      else if(col==3){
        lcd_display_num('B');
      }
    }
     if(row==2){
        if(col==0){
        lcd_display_num('7');
      }
      else if(col==1){
        lcd_display_num('8');
      }
      else if(col==2){
        lcd_display_num('9');
      }
      else if(col==3){
        lcd_display_num('C');
      }
    } 
     if(row==3){
        if(col==0){
        lcd_display_num('*');
      }
      else if(col==1){
        lcd_display_num('0');
      }
      else if(col==2){
        lcd_display_num('#');
      }
      else if(col==3){
        lcd_display_num('D');
      }
    }   
  }
}
}
void lcd_display_num(char num){
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("key pressed:");
  lcd.print(num);
  delay(500);
}