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Re: [avr-gcc-list] Issue with interrupt handler on Atmel Mega 8

From: Jerome Kerdreux
Subject: Re: [avr-gcc-list] Issue with interrupt handler on Atmel Mega 8
Date: Wed, 2 Nov 2005 01:06:12 +0100

On Wed, 02 Nov 2005 00:55:26 +0100
Vincent Trouilliez <address@hidden> wrote:

> On Wed, 2005-11-02 at 00:03 +0100, Jerome Kerdreux wrote:
> > > I'm trying to use the timer 0 on a mega 8.  Everything works fine, 
> > > (I mean, i can see the timer TCNT0 incrementing) but when I want 
> > > to route the interrupt to an handler, I get a infinite reset. 
> I think that's normal. You forgot to include <avr/signals.h>, so the
> "SIG_OVERFLOW0" name was unknown at compile time, and as stated in the
> avr-libc documentation, this does not generate a warning and simply
> defaults the ISR to the bad interrupt vector, which by default generates
> a reset. In the code of your ISR, you put a "return 0" (why?), so the
> "reti" instruction that the compiler generated, never gets executed,
> hence the interrupt flag doesn't get cleared, therefore it instantly
> executes the ISR egain, hence a reset, and so on, forever.
> Why did you put a "return" in your ISR ? Am I missing something very
> subtle ???

Hum, not really funny. I added a return to the ISR because the compilo
give a warning "missing return value for a function". (due to the lack
of SIGNAL macro) 

I read the documentation about the missing-warning if signame is wrong,
so I double-checked the typo, but forget to check that I included signal.h
( Perhaps, somebody can add this to the doc, beside this error is really 
stupid, but can happen if you are a newbie like me) 

Thanks a lot for all answer I get. 

(Apologize for my awfull english) 

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