uint16_t rpm, value=0;
uint32_t cycle=0, trot, icr_l, icr_h;
ISR(TIMER1_CAPT_vect) {
TCNT1H=0;
TCNT1L=0;
icr_l = ICR1L;
icr_h = ICR1H;
trot = (((icr_h << 8) | icr_l)+65536*cycle)*300;
rpm = 60000000/trot;
cycle=0;
}
ISR(TIMER1_OVF_vect) {
cycle++;
}