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Option to use 32768Hz watch crystal for timing. Code suggested by Georg von Zengen.

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This commit is contained in:
dak664 2010-06-18 17:30:30 +00:00
parent e51f03eeb1
commit ab7f3bd8e3
2 changed files with 62 additions and 47 deletions
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46
cpu/avr/dev/clock-avr.h
View file

@ -37,7 +37,44 @@
TIMSK = _BV (OCIE0);
#elif defined (__AVR_ATmega1284P__) || (__AVR_AT90USB1287__) || (__AVR_ATmega1281__)
/*
The Raven has a 32768Hz watch crystal that can be used to clock the timer
while the 1284p is sleeping. The Jackdaw has pads for a crystal. The crystal
can be used to clock the 8 bit timer2.
*/
#if AVR_CONF_USE32KCRYSTAL
#define OCRSetup() \
/* Clock from crystal on TOSC0-1 */ \
ASSR = _BV(AS2); \
\
/* Set counter to zero */ \
TCNT2 = 0; \
\
/* \
* Set comparison register: \
* Crystal freq. is 32768,\
* pre-scale factor is 8, we want 125 ticks / sec: \
* 32768 = 8 * 124.1 * 33, less 1 for CTC mode\
*/ \
OCR2A = 32; \
\
/* \
* Set timer control register: \
* - prescale: 8 (CS21) \
* - counter reset via comparison register (WGM21) \
*/ \
TCCR2A = _BV(WGM21); \
TCCR2B = _BV(CS21); \
\
/* Clear interrupt flag register */ \
TIFR2 = TIFR2; \
\
/* \
* Raise interrupt when value in OCR2 is reached. Note that the \
* counter value in TCNT2 is cleared automatically. \
*/ \
TIMSK2 = _BV (OCIE2A);
#else
#define OCRSetup() \
/* Select internal clock */ \
ASSR = 0x00; \
@ -48,10 +85,10 @@
/* \
* Set comparison register: \
* Crystal freq. is 8000000,\
* pre-scale factor is 1024, i.e. we have 125 "ticks" / sec: \
* 8000000 = 1024 * 125 * 62.5 \
* pre-scale factor is 1024, we want 125 ticks / sec: \
* 8000000 = 1024 * 126.01 * 62, less 1 for CTC mode \
*/ \
OCR0A = 62; \
OCR0A = 61; \
\
/* \
* Set timer control register: \
@ -69,6 +106,7 @@
* counter value in TCNT0 is cleared automatically. \
*/ \
TIMSK0 = _BV (OCIE0A);
#endif /* AVR_CONF_USE32KCRYSTAL */
#define AVR_OUTPUT_COMPARE_INT TIMER0_COMPA_vect

63
cpu/avr/dev/clock.c
View file

@ -6,19 +6,32 @@
#include <avr/io.h>
#include <avr/interrupt.h>
/* RADIOSTATS should be also be defined in the radio driver and webserver */
static volatile clock_time_t count;
static volatile uint8_t scount;
volatile unsigned long seconds;
/* Set RADIOSTATS to monitor radio on time (must also be set in the radio driver) */
#if RF230BB && WEBSERVER
#define RADIOSTATS 1
#endif
#if RADIOSTATS
static volatile clock_time_t count, scount, rcount;
volatile unsigned long seconds,radioontime;
static volatile uint8_t rcount;
volatile unsigned long radioontime;
extern uint8_t RF230_receive_on;
#else
static volatile clock_time_t count, scount;
volatile unsigned long seconds;
#endif
/*
CLOCK_SECOND is the number of ticks per second.
It is defined through CONF_CLOCK_SECOND in the contiki-conf.h for each platform.
The usual AVR default is ~125 ticks per second, counting a prescaler the CPU clock
using the 8 bit timer0.
As clock_time_t is an unsigned 16 bit data type, intervals up to 524 seconds
can be measured with 8 millisecond precision.
For longer intervals a 32 bit global is incremented every second.
clock-avr.h contains the specific setup code for each mcu.
*/
/*---------------------------------------------------------------------------*/
//SIGNAL(SIG_OUTPUT_COMPARE0)
ISR(AVR_OUTPUT_COMPARE_INT)
@ -41,49 +54,13 @@ ISR(AVR_OUTPUT_COMPARE_INT)
}
}
/* External clock source does not work ? */
#if 0
void
clock_init(void)
{
cli ();
TIMSK &= ((unsigned char)~(1 << (TOIE0)));
TIMSK &= ((unsigned char)~(1 << (OCIE0)));
/* Disable TC0 interrupt */
/**
* set Timer/Counter0 to be asynchronous
* from the CPU clock with a second external
* clock(32,768kHz)driving it
*/
ASSR |= (1 << (AS0));
TCCR0 = _BV (CS02) | _BV (CS01) | _BV (WGM1);
TCNT0 = 0;
OCR0 = 128;
TIMSK |= (1 << (OCIE0));
TIMSK |= (1 << (TOIE0));
sei ();
}
#endif
/*---------------------------------------------------------------------------*/
void
clock_init(void)
{
cli ();
OCRSetup();
/*
* Counts the number of ticks. Since clock_time_t is an unsigned
* 16 bit data type, time intervals of up to 524 seconds can be
* measured.
*/
scount = count = 0;
//scount = count = 0;
sei ();
}