Re: [avr-gcc-list] ICP on ATmega8 helpme please

[Galen Seitz]

Ricardo Albarracin B. wrote:
> Hi:
>
> I'have problem with the code: using the AVR-GCC 4.1.1 this code not
> work.
...snip...
> SIGNAL( SIG_INPUT_CAPTURE1 ) {
>         if( !ICES1 ){
>         //Read ICR1 first
>         value_init  = ICR1;
>         TCCR1B |=(1<<ICES1);      // Change to falling edge
>         }
>         if( ICES1 ){
>         //Read ICR1 High byte
>         value_end = ICR1;
>         TCCR1B &=~(1<<ICES1);
>         }
>
>         icp_value = value_end - value_init;
> }
>
>
> void main (void) {
>
>         icp_init();
>
>         while(1){
>         
>         /* send icp_value to serial port */
>         
>         }
> }

In what way does it not work?  Have you declared icp_value as
volatile?
http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_volatile

Is icp_value larger than 8 bits?  If so, you will need to block
interrupts or use some other method of ensuring that the 
interrupt routine doesn't change icp_value while main is reading
it.  This FAQ entry is somewhat applicable.
http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_16bitio

BTW, SIGNAL is deprecated in later versions of avr libc.
http://www.nongnu.org/avr-libc/user-manual/group__avr__interrupts.html

galen