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

[Mike Dodd <>]

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

I'm not familiar with the 7800, but my 7250 code to twiddle DIO bits 
looks similar, excepg ptr is declared as unsigned char*, not unsigned 
long* (CPU difference?).

What frequency square wave are you expecting? Your usleep(1000000)is 
going to give you a one-second period for each state. Flashing the LEDs 
on port E (ptr + 0x24 on the 7250) might be an easier way to test this code.

-- 
Mike

Mike Dodd
Louisa County, VA USA

http://mdodd.com


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