SNx4HC595.cpp

// 2x SNx4HC595 using N bits

#include <Arduino.h>

#define PIN_SER 8
#define PIN_LAT 9
#define PIN_CLK 10

#define TOTAL_BITS 12

void setup()
{
    pinMode(PIN_SER, OUTPUT);
    digitalWrite(PIN_SER, LOW);
    pinMode(PIN_LAT, OUTPUT);
    digitalWrite(PIN_LAT, LOW);
    pinMode(PIN_CLK, OUTPUT);
    digitalWrite(PIN_CLK, LOW);
}

void send(int number)
{
    digitalWrite(PIN_LAT, LOW);

    for (int b = TOTAL_BITS - 1; b >= 0; b--)
    {
        digitalWrite(PIN_CLK, LOW);
        digitalWrite(PIN_SER, number & (1 << b) ? HIGH : LOW);
        digitalWrite(PIN_CLK, HIGH);
    }

    digitalWrite(PIN_LAT, HIGH);
}

void loop()
{
    static int times = 0;
    send(times % (1 << TOTAL_BITS));
    times++;
    delay(20);
}