working on a system like ATM machine.( password , username )
tft screen and keypad is used.
it is driven by number of keypress (i)
but if (buff[15] =='X') but when i didnt do any thing ( without any key press ) this line runs within some time constant.
code may look long but its easy to go through 
#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 buff[15];
long lastUpdate = 0;
int x,i,e,k,xx;
int j=11;
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','X'},
{'4','9','Q','Y'},
{'5','0','E','Z'},
};
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(" User Interface Menu Started! ");
tft.reset();
tft.initDisplay();
}
void(* resetFunc) (void) = 0;
void loop(void)
{
char key = keypad.getKey();
if (key != NO_KEY)
{
buff[i] = key;
i = i+1;
x=x+4;
}
if((millis() - lastUpdate) > 700) // has it been >1 second since the last update?
{
if(i<10)
{
testtext(BLACK);
lastUpdate = millis();
}
if (buff[10] == 'Z' ) // RESET at 10 th press ..................
{
i=0;
testtext8(BLACK) ;
resetFunc();
}
if (buff[10] =='X')
{
testtext5(BLACK);
lastUpdate = millis();
}
}
if ( i==10) // ask user to retry or enter the number inputed
{
testtext2(WHITE);
}
if (buff[10] =='Y') // RETRY
{
i=0;
testtext3(BLACK) ;
resetFunc();
}
if (buff[10] =='X') // STUDENT ID- ok / NOW >>>>>> PASSWORD
{
if(e<10)
{
Serial.print(buff[e]);
e++;
}
}
if ( i==15) // ask Password correct ?????????????????
{
testtext6(WHITE);
}
if (buff[15] =='X') // if CORRECT !!!!!!
{
testtext7(BLACK);
Serial.println();
Serial.print(buff[11]);
Serial.print(buff[12]);
Serial.print(buff[13]);
Serial.print(buff[14]);
Serial.print("#");
}
if (buff[15] =='Y') // if WRONG :(
{ i=11;
testtext5(BLACK);
}
if (buff[15] =='Z') // RESET AT 16 th press
{
i=0;
testtext8(BLACK) ;
resetFunc();
}
}
//------------------------------------------------------------------------------------------------------------------------------------
//-------------------------------------------------------------------------------------------------------------------------------------
void testtext(uint16_t color) // 10 press in the beginning
{
if( i<11 )
{
tft.fillScreen(YELLOW);
tft.setCursor(50, 20);
tft.setTextColor(RED);
tft.setTextSize(2);
tft.println("EEEEEEE");
tft.setCursor(50, 40);
tft.setTextSize(2);
tft.println("STUDENT ID");
tft.setCursor(x, 75);
tft.setTextSize(2);
tft.print(buff);
}
}
void testtext2(uint16_t color) // asking is the number entered is right or wrong
{
// Serial.println("-its 11th press-");
tft.setCursor(60, 100);
tft.setTextColor(GREEN);
tft.setTextSize(2);
tft.drawRect(tft.width() -60, tft.height() -80, 40 , 25, RED);
tft.print(" if correct");
tft.setCursor(60, 120);
tft.print(" press Enter");
tft.setCursor(60, 180);
tft.setTextColor(RED);
tft.drawRect(tft.width() -60 , tft.height() -80, 40 , 30, RED);
tft.print("if wrong ");
tft.setCursor(60, 200);
tft.print("press Cancel");
}
void testtext3(uint16_t color) // if wrong
{
tft.drawRect(0, 0, tft.width(), tft.height(), WHITE);
//tft.drawRect(tft.width() -0, tft.height() -0,240,320, CYAN);
tft.fillRect(0, 0, tft.width(), tft.height(), WHITE);
tft.setCursor(50, 80);
tft.setTextColor(BLUE);
tft.setTextSize(2);
tft.print(" Enter Again ");
}
void testtext4(uint16_t color) // if right ?
{
tft.fillScreen(CYAN);
tft.setCursor(180, 190);
tft.setTextColor(RED);
tft.setTextSize(2);
tft.print(" number is entered");
}
void testtext5(uint16_t color) // PASSWORD INSERTING
{
if(i>10 && i<16)
{
tft.fillScreen(BLACK);
tft.setCursor(50, 50);
tft.setTextColor(RED);
tft.setTextSize(2);
tft.println("ENTER");
tft.setCursor(50, 70);
tft.setTextSize(2);
tft.println("PASSWORD");
tft.setCursor(x, 105);
tft.setTextSize(2);
tft.print( buff[11]);
tft.print( buff[12]);
tft.print( buff[13]);
tft.print( buff[14]);
}
}
void testtext6(uint16_t color) // ask PASSWORD correct ???????
{
// Serial.println("15 th press ");
tft.setCursor(60, 160);
tft.setTextColor(YELLOW);
tft.setTextSize(2);
tft.drawRect(tft.width() -60, tft.height() -80, 40 , 25, RED);
tft.print(" CORRECT");
tft.setCursor(60, 180);
tft.print(" press Enter");
tft.setCursor(60, 200);
tft.setTextColor(RED);
tft.drawRect(tft.width() -60 , tft.height() -80, 40 , 30, RED);
tft.print("WRONG ");
tft.setCursor(60, 220);
tft.print("press Cancel");
}
void testtext7(uint16_t color) // NOW >>>>>> SERIAL >>>>>>>>>>>>>>>>>>>>>>>>>>>>
{
// Serial.println("CONGURATUALTIONS NOW U CAN MOVE ON");
tft.drawRect(0, 0, tft.width(), tft.height(), WHITE);
//tft.drawRect(tft.width() -0, tft.height() -0,240,320, CYAN);
tft.fillRect(0, 0, tft.width(), tft.height(), WHITE);
tft.setCursor(50, 20);
tft.setTextColor(RED);
tft.setTextSize(2);
tft.println("SERIAL COMMUNICATION ");
}
void testtext8(uint16_t color) // RESET
{
Serial.print(" RESET OK ");
tft.drawRect(0, 0, tft.width(), tft.height(), WHITE);
//tft.drawRect(tft.width() -0, tft.height() -0,240,320, CYAN);
tft.fillRect(0, 0, tft.width(), tft.height(), WHITE);
tft.setCursor(50, 80);
tft.setTextColor(BLUE);
tft.setTextSize(2);
//tft.print();
}