nes-proj/cpu/avr/rtimer-arch.h
David Kopf 58298f59db Add F_CPU=0x800000 option with phase lock to external 32768 Hz crystal
Add MCU_CONF_LOW_WEAR option to avoid eeprom writes during development.
2012-01-10 12:42:27 -05:00

72 lines
2.9 KiB
C

/*
* Copyright (c) 2007, Swedish Institute of Computer Science.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
*/
#ifndef __RTIMER_ARCH_H__
#define __RTIMER_ARCH_H__
#include <avr/interrupt.h>
/* Nominal ARCH_SECOND is F_CPU/prescaler, e.g. 8000000/1024 = 7812
* Other prescaler values (1, 8, 64, 256) will give greater precision
* with shorter maximum intervals.
* Setting RTIMER_ARCH_PRESCALER to 0 will leave Timers alone.
* rtimer_arch_now() will then return 0, likely hanging the cpu if used.
* Timer1 is used if Timer3 is not available.
*
* Note the rtimer tick to clock tick conversion will be nominally correct only
* when the same oscillator is used for both clocks.
* When an external 32768 watch crystal is used for clock ticks my raven CPU
* oscillator is 1% slow, 32768 counts on crystal = ~7738 rtimer ticks.
* For more accuracy define F_CPU to 0x800000 and optionally phase lock CPU
* clock to 32768 crystal. This gives RTIMER_ARCH_SECOND = 8192.
*/
#ifndef RTIMER_ARCH_PRESCALER
#define RTIMER_ARCH_PRESCALER 1024UL
#endif
#if RTIMER_ARCH_PRESCALER
#define RTIMER_ARCH_SECOND (F_CPU/RTIMER_ARCH_PRESCALER)
#else
#define RTIMER_ARCH_SECOND 0
#endif
#ifdef TCNT3
#define rtimer_arch_now() (TCNT3)
#elif RTIMER_ARCH_PRESCALER
#define rtimer_arch_now() (TCNT1)
#else
#define rtimer_arch_now() (0)
#endif
void rtimer_arch_sleep(rtimer_clock_t howlong);
#endif /* __RTIMER_ARCH_H__ */