[avr-libc-dev] Disable/Restore all Interrupts

[Sam de Jongh Hepworth]

Hi

avr-libc is great! I have writte two macros that help disable and restore all 
interrupts. I think the cli(); and sei(); macros are a little dangerous to use, 
please consider this;

Before this code is executed all interrupts has been disabled. Now the 
following code is executed;

-- BEGIN --------------------------------
cli();
// do some work with all interrupts disabled...
sei();
-- END --------------------------------

After executing the code all interrupts will be enabled! But they where 
disabled before the code was executed :-(

My solution to this problem is;

-- BEGIN --------------------------------
#define DISABLE_INTERRUPTS() {ubyte _save_int = SREG & flag(7); cli();
#define RESTORE_INTERRUPTS() (SREG |= _save_int);}

DISABLE_INTERRUPTS();
// do some work with all interrupts disabled...
ENABLE_INTERRUPTS();
-- END --------------------------------

The DISABLE_INTERRUPTS macro save the current state of SREG bit 7 and then 
disabled interrupts. The RESTORE_INTERRUPTS macro restore SREG bit 7. Nice!

Best regards,
Sam