Button - INPUT_PULLUP

hi,

i've read somewhere can skip using pullup resistors (or rather use internal ones instead) buttons if use input_pullup constant during pinmode setup  - correct? tried it, results in arduino thinking buttons pressed time (may soldering problem, i'd ensure it's not else first).

this code:

code: [select]

#include <wire.h>
#include <bh1750.h>
#include <liquidcrystal_i2c.h>

liquidcrystal_i2c lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, positive);
bh1750 czujnik_swiatla; //0x23
uint16_t luksy;
int stan_wgore = 0, stan_wdol = 0, stan_onoff = 0;

void clearline(boolean firstline)
{
  if(firstline == false)
    lcd.setcursor(0, 1);
  else
    lcd.setcursor(0, 0);

  for(int = 0; < 16; ++i)
        lcd.write(' ');
}

void setup()
{
  lcd.begin(16, 2); 
  lcd.backlight();
  lcd.setcursor(0, 0);

  czujnik_swiatla.begin();

  pinmode(12, input_pullup);
  pinmode(13, input_pullup);

  pinmode(7, input_pullup);
}

void loop()
{
  clearline(true);
  lcd.setcursor(0, 0);

  stan_wgore = digitalread(12);
  stan_wdol = digitalread(13);
 
  if(stan_wgore == high)
    lcd.print("12");
  else if(stan_wdol == high)
    lcd.print("13");
 
  stan_onoff = digitalread(7);

  clearline(false);
 
  if(stan_onoff == high)
  {
    luksy = czujnik_swiatla.readlightlevel();
 
    lcd.setcursor(0, 1);
    lcd.print(luksy);
  }
}

is correct?

if use pull-up resistors button connect between pin , ground , read low when pressed , high when not pressed.

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