AVR-Chat

On Sun, Apr 10, 2005 at 10:51:01PM -0400, wbounce wrote:

> If have serveral strcmp statements
> 
> Originally I had them all like this.
> 
> if (strcmp("GPGGA",gcBuffer) == 0)
>       {
>       gpFieldPtr=(PGM_P) GGA;
>       }      
> 
> It would execute the pointer assignment on each of the 8 statements
> 
> I changed them to
> 
> lnResult = strcmp("GPGLL",gcBuffer);
> if (lnResult == 0)
>       {
>       gpFieldPtr=GLL;
>       } 
> 
> So I could see the result code of strcmp. This time it skipped the 1st 3
> ok but then started doing the assignments. And when it got to the strcmp
> that should have matched, lnResult was not 0 and yet it did the
> assignment anyhow.
> 
> Anyone have any idea why?

I'm not sure about the problem, but just a quick observation.  With
AVR-GCC, string references like above consume both Flash as well as
precious RAM.  It can add up quickly, too.  To rewrite those to save
RAM space, try:

    strcmp_P(PSTR("GPGLL"),gcBuffer);

This references the string data directly from Flash and saves making a
copy of it to RAM.

-Brian
-- 
Brian Dean
BDMICRO - ATmega128 Based MAVRIC Controllers
http://www.bdmicro.com/