I'm quite new to Arduino world and I'm trying to understand how shift registers work. I built this construction : enter image description here

In fact, it is an Arduino Duemilanove with AtMega on it, but afaik it doesn't matter.

The tutorial I try to follow use SPI library so I try to do it too. I kind of understood that data input, latch and clock had to be pins 7, 4 and 11.

Basically, all I try to do is sending a byte to light the LEDs. As for me now, the sequence should light all LED, then no one, then one after another. I know there is one more input ont the right side of the SR but I didn't plan this model so I ran out of LEDs...

This is the code I use :

#include <SPI.h>
#include <StandardCplusplus.h>
#include <vector>
#include <iterator>
#include <size_type>
using namespace std;
//pin du shift register
#define DATA_PIN 13
#define LATCH_PIN 4
#define CLOCK_PIN 11
//à utiliser plus tard
#define INPUT_PIN 2
void setup() { 
 pinMode(DATA_PIN, OUTPUT);
 pinMode(LATCH_PIN, OUTPUT);
 pinMode(CLOCK_PIN, OUTPUT);
 //pinMode(INPUT_PIN, INPUT);
 SPI.setBitOrder(MSBFIRST);
 SPI.setDataMode(SPI_MODE0);
 SPI.setClockDivider(SPI_CLOCK_DIV2);
 SPI.begin();
 //SPI.transfer(getBit(3));
 //digitalWrite(LATCH_PIN, HIGH);
 //digitalWrite(LATCH_PIN, LOW);
 Serial.begin(9600);
 Serial.println("start !");
}
void loop() {
 shift(B11111111);
 shift(B00000000);
 shift(B10000000);
 shift(B01000000);
 shift(B00100000);
 shift(B00010000);
 shift(B00001000);
 shift(B00000100);
 shift(B00000010);
 shift(B00000001);
}
void shift(int n){
 SPI.transfer(n);
 digitalWrite(LATCH_PIN, HIGH);
 digitalWrite(LATCH_PIN, LOW);
 Serial.print("shift : ");
 Serial.println(n);
 delay(1000);
}

When I upload this code, LEDs sequence has no sense, but serial output was totally OK.

What I see (without the output 0 of course) is : 1111111, 0111111, 1011111, 1110111, 1111101 and then 1111111 without further changes, whereas serial output is 255, 0, 128, 64, 32, 16, 8, 4, 2, 1, 255, 0, 128 and so on.

I assume I didn't understand something important, and it prevent me from finding answers in google.

Thanks for helping, it's really disturbing for me.

EDITS :

changed the title, it is a 74HC595.

Strangest behavior too (not gonna create another topic for that now), I dont have to connect both the gnd and VCC from my arduino for this to light LEDs. It changes a little the brighness of LEDs, but surprisingly VCC< GND< both

This is the tutorial I use to understand shift registers : https://youtu.be/6fVbJbNPrEU?t=195, and the one that uses SPI is nXl4fb_LbcI

I am now aware that I should get one resistor for each LED but I don't have that much resistors and as far as I can see this don't harm my LEDs nor underpower them.