#include <stdio.h>                                                              
#include <fcntl.h>                                                              
#include <sys/mman.h>                                                           
#include <stdint.h>                                                             
                                                                                
static volatile uint32_t *gpio;                                                 
                                                                                
int main(int argc, char **argv)                                                 
{                                                                               
        int fd ;                                                                
                                                                                
        if ((fd = open ("/dev/mem", O_RDWR | O_SYNC) ) < 0) {                   
                printf("Unable to open /dev/mem\n");                            
                return -1;                                                      
        }                                                                       
                                                                                
        gpio = mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd,     
                                                                0x13400000);    
        if (gpio < 0){                                                          
                printf("Mmap failed.\n");                                       
                return -1;                                                      
        }                                                                       
                                                                                
        // Print GPX1 configuration register.                                   
        printf("GPX1CON register : 0x%08x\n",                                   
                                *(unsigned int *)(gpio + (0x0c20 >> 2)));       
                                                                                
        // Set direction of GPX1.2 configuration register as out.               
        *(gpio + (0x0c20 >> 2)) |= (0x1 << 8);                                  
        printf("GPX1CON register : 0x%08x\n",                                   
                                *(unsigned int *)(gpio + (0x0c20 >> 2)));       
        // GPX1.2 High                                                          
        *(gpio + (0x0c24 >> 2)) |= (1 << 2);                                    
        printf("GPX1DAT register : 0x%08x\n",                                   
                                *(unsigned int *)(gpio + (0x0c24 >> 2)));       
        // GPX1.2 Low                                                           
        *(gpio + (0x0c24 >> 2)) &= ~(1 << 2);                                   
        printf("GPX1DAT register : 0x%08x\n",                                   
                                *(unsigned int *)(gpio + (0x0c24 >> 2)));       
                                                                                
        return 0;                                                               
}