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