Re: [ts-7000] Problem with DIO header of TS 7800

[Jim Jackson <>]

On Sat, 17 Mar 2012, charliewxj wrote:

> Hello, I just started using TS 7800 board. I just want to use DIO header to 
> create a square wave. I tried to write a C code but it didn't succeed. I need 
> help from all of you.
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/stat.h>
> #include <sys/mman.h>
> #include <unistd.h>
> #include <fcntl.h>
> 
> int main(void)
> {
> 
>       char input;
>       int fd;
>       unsigned long *ptr;
>       unsigned long *dr;

try defining pointers as volatile

> 
>       printf("begin, square wave.\n");
> 
>       fd= open("/dev/mem",O_RDWR) ;  
> 
>       ptr = 
> mmap(NULL,getpagesize(),PROT_READ|PROT_WRITE,MAP_SHARED,fd,0xe8000000);
> 
>       dr =ptr + 0x4;  // 0x4 offset

I don't know the memory map of 7800, but here you are index the 4th integer 
(23bits) from ptr. If you want the 4th byte then redefine your pointers as 
unsigned char * , or divide the byte offset by 4.


>       *dr=*dr & 0x0000;
>       while(1)
>       {
>               usleep(1000000);
>               *dr= ~ *dr;
>       }
> 
>       return 0;
> }
> 
> 
> 
> 
> 


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