rtgpio.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <sys/mman.h>

#include <native/task.h>
#include <native/timer.h>

#define TIMESLEEP 10000

static volatile uint32_t *gpio;

RT_TASK blink_task;
int fd;

void blink(void *arg __attribute__((__unused__)))
{

    int iomask = 0;

    rt_task_set_periodic(NULL, TM_NOW, TIMESLEEP);

    while(1) {
        rt_task_wait_period(NULL);

        if( iomask == 0 ) {
            *gpio &= ~(1 << 8);
            iomask = 1;
        }
        else {
            *gpio |= (1 << 8);
            iomask = 0;
        }
    }
}

void catch_signal() {}

int main(void)
{
    signal(SIGTERM, catch_signal);
    signal(SIGINT, catch_signal);

    /* Avoids memory swapping for this program */
    mlockall(MCL_CURRENT|MCL_FUTURE);

    //Obtain handle to physical memory
    if ((fd = open ("/dev/mem", O_RDWR | O_SYNC) ) < 0) {
        printf("Unable to open /dev/mem: %s\n", strerror(errno));
        return -1;
    }

    gpio = (uint32_t *)mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x20ac000);

    if ((int32_t)gpio < 0){
        printf("Mmap failed: %s\n", strerror(errno));
        return -1;
    }

    //set gpio8 as an output
    //increment the pointer to 0x20ac004
    *(gpio + 4) |= (1 << 8);

    /* Task Creation */
    rt_task_create(&blink_task, "blinkLed", 0, 99, 0);

    rt_task_start(&blink_task, &blink, NULL);

    getchar();
    rt_task_delete(&blink_task);

    //close(fd);

    return 0;
}