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[avr-libc-dev] empty interrupts

From: Artur Lipowski
Subject: [avr-libc-dev] empty interrupts
Date: Fri, 11 Apr 2003 08:20:16 +0200


Sometimes we need to enable interrupt but nothing should be done in the ISR
(eg. using ADC noise canceler function).
Declaring a standard SIGNAL macro and leaving empty body works fine but...
There is still generated prolog and epilog for ISR and a few words of FLASH
is lost as weel as a few CPU cycles. I know this is nothing importand but
sometimes it can be significant.
Because of above I use in my projects following defines:

#ifdef __cplusplus
#define EMPTY_INTERRUPT(signame)            \
extern "C" void signame(void);                          \
void signame (void) __attribute__((naked)) ;      \
void signame (void) {  __asm__ __volatile__ ("reti" ::); }
#define EMPTY_INTERRUPT(signame)                \
void signame (void) __attribute__((naked)) ;           \
void signame (void) { __asm__ __volatile__ ("reti" ::); }

and obvious usage:

What about adding this to the avr-libc?

Artur Lipowski

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