Arduino: Obfuscate LCD characters

Test.c

// https://twitter.com/giltesa/status/1003716194778714115

#include <LiquidCrystal.h>
#include <MultiTaskLib.h>

LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
MultiTask multitask(20);
const byte ROW = 1;


void setup()
{
  lcd.begin(16, 2);
  lcd.print("Enter password:");

  Serial.begin(9600);
}


void loop()
{
    static byte col = 0;
    static char btn;

    multitask.Update();
    btn = readButton();

    if( btn != '#' )
    {
        lcd.setCursor(col, ROW);
        lcd.print(btn);

        uint8_t var = multitask.AddSingle(1000, [](){ obfusChar(col); });
        Serial.print("ID = ");
        Serial.println(var);

        col = (col+1 < 16 ? col+1 : 0);
    }
}


void obfusChar( const byte col )
{
    Serial.print("COL = ");
    Serial.println(col);

    lcd.setCursor(col, ROW);
    lcd.print("*");
}


char readButton()
{
    char result = '#';
    int val     = analogRead(0);

    if( val < 50 )
        result = 'R';
    else if( val < 250 )
        result = 'U';
    else if( val < 450 )
        result = 'D';
    else if( val < 650 )
        result = 'L';
    else if( val < 850 )
        result = 'S';

    while( result != '#' && analogRead(0) < 1000 );
    return result;
}

Test2.c

// https://twitter.com/giltesa/status/1003743414192615424

#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
String password = "";
const byte ROW = 1;
char btn;


void setup()
{
  lcd.begin(16, 2);
  lcd.print("Enter password:");
}


void loop()
{
    btn = readButton();

    if( btn != '#' )
    {
        byte length = password.length();

        if( length <= 15 )
        {
            password.concat(btn);

            for( int i=0 ; i <= length ; i++ )
            {
                lcd.setCursor(i, ROW);
                lcd.print(i < length ? '*' : password.charAt(i));
            }
        }
    }
}


char readButton()
{
    char result = '#';
    int val     = analogRead(0);

    if( val < 50 )
        result = 'R';
    else if( val < 250 )
        result = 'U';
    else if( val < 450 )
        result = 'D';
    else if( val < 650 )
        result = 'L';
    else if( val < 850 )
        result = 'S';

    while( result != '#' && analogRead(0) < 1000 );
    return result;
}