74hc165 works crazy

[system]

Hi, guys. First time i'm trying to use input shift register IN74HC165AN

I Plugged it to ARDUINO and use this code

#include <SPI.h>

enum { REG_LATCH = 8 };


void setup()
{
  Serial.begin(9600);
  SPI.begin();

  pinMode(REG_LATCH, OUTPUT);
  digitalWrite(REG_LATCH, HIGH);
}


void loop()
{
  static uint8_t last_input_states = 0;

  digitalWrite(REG_LATCH, LOW);
  digitalWrite(REG_LATCH, HIGH);

  uint8_t states = SPI.transfer(0);

 
  if (states != last_input_states)
  {
 
    uint8_t changed = states ^ last_input_states;
    last_input_states = states; // ?????????? ??????? ?????????

    for (int i = 0; i < 8; ++i)
    {
      if (changed & 1) // ???? ????????? ?????? ??????????…
      {
        Serial.print("#");
        Serial.print(i); // ???? ????? ??????
        Serial.print(" -> ");
        Serial.println(states & 1); // … ? ????? ?????????
      }
      changed >>= 1;
      states >>= 1;
    }
  }
}

The problem is - in serial port i see every millsecond changes! The data randomly changes. But! I do not even plag any buttons! Why data is changing?

[MAS3]

If that is your actual schematics, then your inputs are floating.
Use pull up resistors or pull down resistors (whatever suits your needs).

[system]

Thank you! But, where i should connect them?

[MarkT]

To the floating inputs! Try 10k resistors - if the resistor goes to GND, have the push-button go
to 5V (or vice versa).

CMOS inputs have infinite input resistance (almost, 10^10 ohms or so) and will pickup
any nearby signals via stray capacitance if left "floating".

[system]

I plugged this way but it still send random data& ((((