How to control N900's GPIO? - maemo.org

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justforfun	2011-09-21 , 15:33
Posts: 58 \| Thanked: 8 times \| Joined on Aug 2010	#1

I think this is a very basic but important question.
I did a trial just now but failed. The code is below.
GPIO 0x48002110 is the CAM_B_EN signal of N900, which could change the camera to A or B. If success, when you open N900's camera application(that's camera A, the big one), it will be influenced due to 1/0 in turn each 1000ms.

Then I compile it in the scratchbox and upload it to N900. When running it, below feedback comes.

Code:

Nokia-N900:~# ./gpio 
Segmentation fault

Can anyone help to find the reason? Thanks!

Code:

#include <sys/types.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <memory.h>

#define GPIO 0x48002110
#define INT *(volatile unsigned int*)

void *map_base;
int n,fd;

int main(int argc,char *argv[])
{
    if((fd=open("/dev/mem",O_RDWR | O_SYNC))==-1){
    perror("open error!\n");
    return(-1);
    }

    map_base = mmap(0,0xff,PROT_READ | PROT_WRITE,MAP_SHARED,fd,GPIO);
    while(1){
	INT(map_base) = 1; //set it high
	sleep(1000);
	INT(map_base) = 0; //set it low
        sleep(1000);
    }

    close(fd);   

    munmap(map_base,0xff);
}