AVR Freaks

	// real time clock configuration
	sysclk_enable_module(SYSCLK_PORT_GEN, SYSCLK_RTC);
	//Wait until RTC is stable
	CLK.RTCCTRL = CLK_RTCSRC_TOSC_gc | CLK_RTCEN_bm;
	//CLK.RTCCTRL = CLK_RTCSRC_RCOSC_gc | CLK_RTCEN_bm; // this works
	while (RTC.STATUS & RTC_SYNCBUSY_bm);
	RTC.PER = 1023;
	RTC.CNT = 0;
	RTC.COMP = 0;
	
	/* Since overflow interrupt is needed all the time we limit sleep to
	 * power-save.
	 */
	sleepmgr_lock_mode(SLEEPMGR_PSAVE);
	RTC.INTCTRL = RTC_OVFINTLVL_LO_gc;
	RTC.CTRL = RTC_PRESCALER_DIV1_gc;	


// RTC timer overflow
ISR(RTC_OVF_vect)
{
	LED_PORT.OUTTGL = LED1;
}