#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/io.h>
#include <stdint.h>
#include <string.h>

int main(void)
{
    unsigned char val;
    if (ioperm(0xA45, 1, 1) < 0 || ioperm(0xA46, 1, 1) < 0 || ioperm(0xEB, 1, 1) < 0) {
        perror("Failed to request I/O port permission");
        return 1;
    }    

    outb(0x00,0xA45);
    outb(inb(0xA46) | 0x40, 0xA46);//update VBAT

    outb(0x00,0xEB);
    outb(0x00,0xEB);
    outb(0x00,0xEB);

    outb(0x28,0xA45);
    val = inb(0xA46);//read VBAT    

    printf("VBAT value = %dmv\n", val * 2 * 11);
}