store the keypad press sequence as a data- arduino

#define LCD_CS A3 
#define LCD_CD A2   
#define LCD_WR A1   
#define LCD_RD A0   

#define LCD_RESET A4

#define   BLACK           0x0000
#define   BLUE            0x001F
#define   RED             0xF800
#define   GREEN           0x07E0
#define CYAN            0x07FF
#define MAGENTA         0xF81F
#define YELLOW          0xFFE0
#define WHITE           0xFFFF

#include "TFTLCD.h"
#include <Keypad.h>

const byte ROWS = 5;
const byte COLS = 4;
char buffer;
long lastUpdate = 0;
int x;

TFTLCD tft(LCD_CS, LCD_CD, LCD_WR, LCD_RD, LCD_RESET);

char keys[ROWS][COLS] =
{
  {'1','6','A','D'},
  {'2','7','B','E'},
  {'3','8','C','F'},
  {'4','9','X','Y'},
  {'5','0','Z','R'},
 
};

byte rowPins[ROWS] = {40,39,38,37,36}; //connect to row pinouts
byte colPins[COLS] = {32,33,34,35}; //connect to column pinouts

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup(void)
{
  Serial.begin(9600);
  Serial.println("8 Bit LCD test!");
  tft.reset();
  tft.initDisplay();

}

void loop(void)
{
  char key = keypad.getKey();

  if (key != NO_KEY) 
  {
    Serial.print(key); 
    buffer=key;
  }
  /*testtext(BLACK);
   delay(1000); */
   
  if((millis() - lastUpdate) > 100)  // has it been >1 second since the last update?
  {
    testtext(BLACK);  // update display
    lastUpdate = millis();
  x=x+8;  // remember the time
  }

}
//int y = (10*x);
// for TFT screen display letters
void testtext(uint16_t color)
{
  tft.fillScreen(CYAN);
  tft.setCursor(50, 20);
  tft.setTextColor(RED);
  tft.setTextSize(2);
  tft.println("HI TEXTS BELOW");
  
 
  tft.setCursor(x, 50);
  tft.setTextSize(3);
  tft.print(buffer);

}