#include <stdio.h>
#include "AT91SAM7S256.h"
#include "at91_sysc.h"
#include "board.h"

static void rtt_isr(uint32_t status)
{
	*AT91C_RTTC_RTAR = *AT91C_RTTC_RTVR +1;

	static uint32_t i;
	*AT91C_PIOA_SODR = i;
	i = i ^ LED_ORANGE;
	*AT91C_PIOA_CODR = i;
}

void at91_rttc_test_init(void)
{
	/* calculate SLOWCK from MAINCK and measured MAINF */
	uint32_t prescaler = MAINCK * 16 / (*AT91C_CKGR_MCFR & AT91C_CKGR_MAINF);

	sysc_register_isr(AT91_SYSIRQ_RTT, &rtt_isr);

	/*
	 * AT91C_RTTC_RTTINCIEN doesn't work
	 * use AT91C_RTTC_ALMIEN and increment RTAR in isr
	 */
	*AT91C_RTTC_RTAR = *AT91C_RTTC_RTVR +1;
	*AT91C_RTTC_RTMR = (AT91C_RTTC_RTPRES & prescaler) |
			   AT91C_RTTC_ALMIEN |
			   AT91C_RTTC_RTTRST;

	printf("rttc running at %ld Hz\n\r", prescaler);
}