cubieboard 全志A10 Cortex-A8开发板 点亮板载蓝色LED

参考：http://www.cubieforums.com/index.php?topic=253.10;wap2

代码如下：

///////////////////////////////////////////////////////////////////////////////
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <time.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/select.h>
#include <pthread.h>
#include <unistd.h>
#include <sched.h>
#include <errno.h>


#define SW_PORTC_IO_BASE  0x01c20800

int main() {
   unsigned int * pc;
   int fd, i;
   char * ptr;
   unsigned int addr_start, addr_offset, PageSize, PageMask, data;

   PageSize = sysconf(_SC_PAGESIZE);
   PageMask = (~(PageSize-1));
   addr_start = SW_PORTC_IO_BASE & PageMask;
   addr_offset = SW_PORTC_IO_BASE & ~PageMask;

   fd = open("/dev/mem", O_RDWR);
   if(fd < 0) {
      perror("Unable to open /dev/mem");
      return(-1);
   }

   pc = mmap(0, PageSize*2, PROT_READ|PROT_WRITE, MAP_SHARED, fd, addr_start);

   if(pc == MAP_FAILED) {
      perror("Unable to mmap file");
      printf("pc:%lx
", (unsigned long)pc);
      return(-1);
   }
   printf("PageSize:%8.8x	PageMask:%8.8x
addr_start:%8.8x	addr_offset:%8.8x
",PageSize,PageMask,addr_start,addr_offset);
   printf("pc:%8.8x
", *(unsigned int *)pc);
   ptr = (char *)pc + addr_offset;
   data = *(unsigned int *)(ptr+0x10c);
   for(i=0;i<1000;i++){
      data |= 1<<21; //blue led
      *(unsigned int *)(ptr+0x10c) = data;
      usleep(100000);
      data &= ~(1<<21);
      *(unsigned int *)(ptr+0x10c) = data;
      usleep(500000);
   }
   


   //debug
   //printf("cfg2=0x%8.8x pul1=0x%8.8x drv1=0x%8.8x data=0x%8.8x
",   *(unsigned int *)(ptr+0x104),*(unsigned int *)(ptr+0x11c),*(unsigned int *)(ptr+0x114),*(unsigned int *)(ptr+0x10c));
   close(fd);
   return 0;
}

分析：

参照cubieboard开发板的用户手册，我们可以知道PIO的基地址是0x01c20800，但是mmap函数映射是以页为单位进行映射的，因此要做一个转换sysconf()函数就是得到系统页大小的，然后进行一系列的转换，然后通过mmap（）函数来得到对应的io映射地址，然后进行操作。