Re: [avr-gcc-list] Global variables and ISRs ???

[Lars Noschinski]

* Vincent Trouilliez <address@hidden> [2005-09-06 21:37]:
> Problem : on my ATmega32, after several experiments (only just started
> using it, learning...), I am suffering a big problem. It seems that when
> I declare a variable as global, then modify it within an interrupt
> routine, the 'main' function can't see that the variable has been
> modified, as if it weren't a global variable... hmmm.

You must declare the global variable as volatile (or as register), if
you want to modify in an ISR.

So replace

   unsigned char flag, bin;  //global variables

by

   volatile unsigned char flag, bin;