sam7fc/src/at91_rttc_test.c

/***************************************************************************
 *   sam7fc - Real Time Clock Calibration                                  *
 *                                                                         *
 *   Copyright (C) 02/2008 by Olaf Rempel                                  *
 *   razzor@kopf-tisch.de                                                  *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; version 2 of the License                *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#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;
}

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);
}