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Add F_CPU=0x800000 option with phase lock to external 32768 Hz crystal

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Add MCU_CONF_LOW_WEAR option to avoid eeprom writes during development.
This commit is contained in:
David Kopf 2012-01-10 12:42:27 -05:00
parent 057398a6d1
commit 58298f59db
7 changed files with 95 additions and 5 deletions
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8
cpu/avr/rtimer-arch.h
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@ -28,7 +28,6 @@
*
* This file is part of the Contiki operating system.
*
* $Id: rtimer-arch.h,v 1.5 2010/02/18 17:21:44 dak664 Exp $
*/
#ifndef __RTIMER_ARCH_H__
@ -42,6 +41,13 @@
* 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