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/*
* Copyright © 2012 Keith Packard <keithp@keithp.com>
*
* 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; either version 2 of the License, or
* (at your option) any later version.
*
* 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 <ao.h>
volatile AO_TICK_TYPE ao_tick_count;
static volatile AO_TICK_TYPE ao_wakeup_count;
ISR(TIMER1_COMPA_vect)
{
++ao_tick_count;
if ((int16_t) (ao_tick_count - ao_wakeup_count) >= 0)
ao_wakeup((void *) &ao_tick_count);
}
uint16_t
ao_time(void)
{
uint16_t r;
cli();
r = ao_tick_count;
sei();
return r;
}
#if AVR_CLOCK == 8000000UL
#define AO_CLKPS 0 /* divide by 1 */
#define AO_CS 10 /* prescale by 512 */
#endif
#if AVR_CLOCK == 4000000UL
#define AO_CLKPS 1 /* divide by 2 */
#define AO_CS 9 /* prescale by 256 */
#endif
#if AVR_CLOCK == 2000000UL
#define AO_CLKPS 2 /* divide by 4 */
#define AO_CS 8 /* prescale by 128 */
#endif
#if AVR_CLOCK == 1000000UL
#define AO_CLKPS 3 /* divide by 8 */
#define AO_CS 7 /* prescale by 64 */
#endif
#if AVR_CLOCK == 500000UL
#define AO_CLKPS 4 /* divide by 16 */
#define AO_CS 6 /* prescale by 32 */
#endif
#if AVR_CLOCK == 250000UL
#define AO_CLKPS 5 /* divide by 32 */
#define AO_CS 5 /* prescale by 16 */
#endif
#if AVR_CLOCK == 125000UL
#define AO_CLKPS 6 /* divide by 64 */
#define AO_CS 4 /* prescale by 32 */
#endif
#if AVR_CLOCK == 62500UL
#define AO_CLKPS 7 /* divide by 128 */
#define AO_CS 4 /* prescale by 32 */
#endif
void
ao_timer_init(void)
{
cli();
CLKPR = (1 << CLKPCE);
CLKPR = (AO_CLKPS << CLKPS0);
sei();
/* Overall division ratio is 512 * 125,
* so our 8MHz base clock ends up as a 125Hz
* clock
*/
TCCR1 = ((1 << CTC1) | /* Clear timer on match */
(0 << PWM1A) | /* Not PWM mode */
(0 << COM1A0) | /* Don't change output pins */
(0 << COM1A1) | /* ... */
(AO_CS << CS10)); /* Prescale */
GTCCR = ((0 << PWM1B) | /* Not PWM mode */
(0 << COM1B1) | /* Don't change output pins */
(0 << COM1B0) | /* ... */
(0 << FOC1B) | /* Don't force output compare */
(0 << FOC1A) | /* ... */
(0 << PSR1)); /* Don't bother to reset scaler */
OCR1A = 0;
OCR1B = 0;
OCR1C = 124; /* Divide by as many 5s as we can (5^3 = 125) */
TIMSK = ((1 << OCIE1A) | /* Enable TIMER1_COMPA interrupt */
(0 << OCIE1B) | /* Disable TIMER1_COMPB interrupt */
(0 << TOIE1)); /* Disable TIMER1_OVF interrupt */
DDRB |= 2;
}
#define PER_LOOP 8
#define US_LOOPS ((AVR_CLOCK / 1000000) / PER_LOOP)
void ao_delay_us(uint16_t us)
{
#if US_LOOPS > 1
us *= US_LOOPS;
#endif
for (;;) {
ao_arch_nop();
ao_arch_nop();
ao_arch_nop();
--us;
/* A bit funky to keep the optimizer
* from short-circuiting the test */
if (!((uint8_t) (us | (us >> 8))))
break;
}
}
void
ao_delay_until(uint16_t target)
{
cli();
ao_wakeup_count = target;
while ((int16_t) (target - ao_tick_count) > 0)
ao_sleep((void *) &ao_tick_count);
sei();
}
void
ao_delay(uint16_t ticks)
{
ao_delay_until(ao_time() + ticks);
}
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