Make pretty lights using a Raspberry Pi and a 74374N octal flip-flop

74374n-raspberry-pi.c

#define _BSD_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define INPUT 17
#define OE 18
#define CLK 27

void setup_pin(int pin) {
    FILE *f;
    char buf[512] = {0};
    f = fopen("/sys/class/gpio/export", "w");
    fprintf(f, "%d\n", pin);
    fclose(f);
    sprintf(buf, "/sys/class/gpio/gpio%d/direction", pin);
    f = fopen(buf, "w");
    fprintf(f, "out\n");
    fclose(f);
}

void set_pin(int pin, int value) {
    FILE *f;
    char buf[512] = {0};
    sprintf(buf, "/sys/class/gpio/gpio%d/value", pin);
    f = fopen(buf, "w");
    fprintf(f, "%d\n", value);
    fclose(f);
}

int main(void) {
    setup_pin(CLK);
    setup_pin(OE);
    setup_pin(INPUT);
    set_pin(OE, 0);
    while(1) {
        for(int i = 0; i < 8; i++) {
            set_pin(CLK, 0);
            set_pin(INPUT, random() & 1);
            set_pin(CLK, 1);
        }
        sleep(1);
    }
    return 0;
}