[avr-gcc-list] External interrupt doesn't react

[Bart Friederichs]

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Hi,

I have been experimenting with external interrupts, but I don't seem to 
get it working. I am using an ATmega16 and avr-gcc version 3.3.1

The code I use is as follows:

/*
* Timer test ground
*/

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/signal.h>

SIGNAL (SIG_INTERRUPT0) {
 PORTA = 0x00;
}

int main() {
 /* init ports */
 DDRA = 0xFF;
 PORTA = 0x01;

 /* set INT0 to request interrupt at rising edge */
 enable_external_int(BV(INT0));

 /* enable interrupts */
 sei();

 for(;;);

 return 0;
}

It should light up a LED connected to PIN 1 of PORT A. Then, when I pull 
the INT0 (pin 16 on the ATMega16) high, the LED should go off. However, 
after compiling and downloading this, only the LED lights up, and 
nothing happens when I pull the INT0 hi.

Some problems:
1. What should the 'mask' be in calling 'enable_external_int()' ?
2. I replaced enable_external_int() with  

 MCUCR = (1<<ISC01) | (1<<ISC00);
 GICR = (1<<INT0);

 Still, no luck.


I cannot find any clear examples on how to use external interrupts on 
the net and the document by Rich Neswold isn't very clear on the 'mask' 
to be given to enable_external_int().

Can anybody give me some clues?

Thanks in advance,
Bart

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