#include <stdint.h>

#define GPIO_BASE 0x40000000u

static volatile uint32_t * const gpio = (volatile uint32_t *)GPIO_BASE;

static void delay(volatile uint32_t ticks){
    while (ticks--) {
        __asm__ volatile ("nop");
    }
}

int main(void)
{
    uint32_t v = 0;

    for (;;) {
        *gpio = v;
        v++;
        delay(20000u);
    }
}