#include <LiquidCrystal_I2C.h>
#include <Wire.h>
  
  LiquidCrystal_I2C lcd(0x27,20,4);

  const int R1=12,R2=11,R3=10,R4=9;
  const int C1=7,C2=6,C3=5,C4=4;
  char key;
//--------------------------------------------------
void setup() {
  Serial.begin(115200);
  lcd.init();
  lcd.backlight();
   pinMode(R1, OUTPUT);
   pinMode(R2, OUTPUT);
   pinMode(R3, OUTPUT);
   pinMode(R4, OUTPUT);
   pinMode(C1 , INPUT_PULLUP);
   pinMode(C2 , INPUT_PULLUP);
   pinMode(C3 , INPUT_PULLUP);
   pinMode(C4 , INPUT_PULLUP);
  digitalWrite(C1,HIGH);
  digitalWrite(C2,HIGH);
  digitalWrite(C3,HIGH);
  digitalWrite(C4,HIGH);

};
//-------------------------------------------------------
void loop() {
 ROW1();
 ROW2();
 ROW3();
 ROW4();
 lcd.setCursor(0,0);
 lcd.print("Your pressed  : ");
 lcd.print(key);
 };
//---------------------------------------------------------
void ROW1() {
  //-----------ROW1-------//
digitalWrite(R1, LOW);
  digitalWrite(R2, HIGH);
  digitalWrite(R3, HIGH);
  digitalWrite(R4, HIGH);
  if (digitalRead(C1)==LOW) {
    key = '1';
    delay(200);
  }

else if (digitalRead(C2)==LOW) {
    key = '2';
    delay(200);
  }

else if (digitalRead(C3)==LOW) {
   key = '3';
    delay(200);
  }

else if (digitalRead(C4)==LOW) {
    key = 'A';
    delay(200);
  }
};
//--------------------------------------------------
void ROW2() {
//------------ROW2-----------//
digitalWrite(R1, HIGH);
  digitalWrite(R2, LOW);
  digitalWrite(R3, HIGH);
  digitalWrite(R4, HIGH);
  if (digitalRead(C1)==LOW) {
    key = '4';
    delay(200);
  }

else if (digitalRead(C2)==LOW) {
    key  = '5';
    delay(200);
  }

else if (digitalRead(C3)==LOW) {
    key = '6';
    delay(200);
  }

else if (digitalRead(C4)==LOW) {
  key = 'B';
    delay(200);
  }
//------------------------------------------------------
};
void ROW3(){
//---------ROW3----------//
digitalWrite(R1, HIGH);
  digitalWrite(R2, HIGH);
  digitalWrite(R3, LOW);
  digitalWrite(R4, HIGH);
  if (digitalRead(C1)==LOW) {
    key = '7';
    delay(200);
  }

else if (digitalRead(C2)==LOW) {
    key  = '8';
    delay(200);
  }

else if (digitalRead(C3)==LOW) {
    key = '9';
    delay(200);
  }

else if (digitalRead(C4)==LOW) {
  key = 'C';
    delay(200);
  }
};
void ROW4() {
 //------------ROW4--------//
digitalWrite(R1, HIGH);
  digitalWrite(R2, HIGH);
  digitalWrite(R3, HIGH);
  digitalWrite(R4, LOW);
  if (digitalRead(C1)==LOW) {
    key = '*';
    delay(200);
  }

else if (digitalRead(C2)==LOW) {
    key  = '0';
    delay(200);
  }

else if (digitalRead(C3)==LOW) {
    key = '#';
    delay(200);
  }

else if (digitalRead(C4)==LOW) {
  key = 'D';
    delay(200);
  }
};