45 lines
783 B
C
45 lines
783 B
C
#include <stdint.h>
|
|
#include <stdbool.h>
|
|
#include <avr/io.h>
|
|
#include <avr/interrupt.h>
|
|
#include "avr.h"
|
|
|
|
/* Clock must be a multiple of 2MHz or there will be clock drift */
|
|
#define TICK_HZ (CLOCK_HZ / 8 / 64)
|
|
#define TICKS_PER_JIFFY (TICK_HZ / 10)
|
|
|
|
#define cbi(byt, bit) (byt &= ~_BV(bit))
|
|
#define sbi(byt, bit) (byt |= _BV(bit))
|
|
|
|
extern volatile bool tick;
|
|
extern volatile uint32_t jiffies;
|
|
|
|
// Interrupt called every jiffy
|
|
ISR(TIM1_COMPA_vect)
|
|
{
|
|
jiffies += 1;
|
|
tick = true;
|
|
}
|
|
|
|
void
|
|
init(void)
|
|
{
|
|
int i;
|
|
|
|
DDRA = ~(_BV(NESOUT));
|
|
DDRB = 0xff;
|
|
|
|
TCCR1A = 0;
|
|
TCCR1B = 0;
|
|
TCNT1 = 0; // reset counter
|
|
|
|
OCR1A = TICKS_PER_JIFFY - 1;
|
|
TCCR1B |= _BV(WGM12);
|
|
TCCR1B |= _BV(CS11) | _BV(CS10); // prescale: clk_io / 64
|
|
TIMSK1 |= _BV(OCIE1A);
|
|
|
|
bit(PORTA, _BV(7), true);
|
|
|
|
sei();
|
|
}
|