AVR-Chat

On Thu, Mar 22, 2007 at 11:28:53AM -0400, Mike Bronosky wrote:
> All this is fine. But for many of us hobbyists that know just enough
> about C, especially when it comes to AVRs, to be
> down-right-dangerous...
> 
> For me something like the following, is good, proper and works. It is not
> fully understood until I dissect.
> while ((UCSRA & (1<<UDRE))==0);
> 
> while(UCSRA.5 == 0);  //while(USART Data Register Empty)
> Haven't tried this but I think it should work and means "while the
> data register is empty sit right here".

*I* see what you intend but I don't think the compiler will. "5 is not a
member of the struct UCSRA". In fact UCSRA isn't a struct at all so the
dot thing won't work.

Also suggest one pretty-print the while() usage something like this so
that it stands out like a sore thumb that one has a small loop:

	while ((UCSRA & (1<<UDRE))==0)
		;

> Now to the Xsperts may disagree. I'm a hobbiest, it works for me and
> best of all I understand why it works.

As a general rule its always bad to write loops with only one possible
exit. At the least you should provide a time out exit. Or enable the
watchdog timer and kick the dog once prior to entering the above loop.

-- 
David Kelly N4HHE, dkelly@HiWAAY.net
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Whom computers would destroy, they must first drive mad.