[avr-libc-dev] volatie with winavr2010

[Leiu]

here is my code:
volatile uint8_t first_edge = 'A';
.................................
ISR(TIMER1_OVF_vect)
{
if(first_edge <= 'Z')
{
avr2pc(first_edge); //avr2pc to transmit character to PC via COM port
++first_edge;
}else
{
first_edge = 'A';
}

}

my result:
I only show 'A' in hyperterminal :
=> first_edge can;