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/*
* Copyright © 2011 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; version 2 of the License.
*
* 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 <avr/io.h>
#include <avr/interrupt.h>
#define F_CPU 16000000UL // 16 MHz
#include <util/delay.h>
#define LEDOUT PORTB7
#define LEDPORT PORTB
#define LEDDDR DDRB
#define LEDDDRPIN DD7
ISR(TIMER1_COMPA_vect)
{
static int x;
if (++x > 50) {
x = 0;
LEDPORT ^= (1 << LEDOUT);
}
}
static void
timer_init(void)
{
TCCR1A = ((0 << WGM11) | /* CTC mode, OCR1A */
(0 << WGM10)); /* CTC mode, OCR1A */
TCCR1B = ((0 << ICNC1) | /* no input capture noise canceler */
(0 << ICES1) | /* input capture on falling edge (don't care) */
(0 << WGM13) | /* CTC mode, OCR1A */
(1 << WGM12) | /* CTC mode, OCR1A */
(3 << CS10)); /* clk/64 from prescaler */
OCR1A = 2500; /* 16MHz clock */
// OCR1A = 1250; /* 8MHz clock */
TIMSK1 = (1 << OCIE1A); /* Interrupt on compare match */
}
static void
clock_init(void)
{
/* disable RC clock */
CLKSEL0 &= ~(1 << RCE);
/* Disable PLL */
PLLCSR &= ~(1 << PLLE);
/* Enable external clock */
CLKSEL0 |= (1 << EXTE);
/* wait for external clock to be ready */
while ((CLKSTA & (1 << EXTON)) == 0)
;
/* select external clock */
CLKSEL0 |= (1 << CLKS);
/* Disable the clock prescaler */
cli();
CLKPR = (1 << CLKPCE);
CLKPR = 0;
sei();
/* Set up the PLL to use the crystal */
/* Use primary system clock as PLL source */
PLLFRQ = ((0 << PINMUX) | /* Use primary clock */
(0 << PLLUSB) | /* No divide by 2 for USB */
(0 << PLLTM0) | /* Disable high speed timer */
(0x4 << PDIV0)); /* 48MHz PLL clock */
/* Set the frequency of the crystal */
PLLCSR |= (1 << PINDIV); /* For 16MHz crystal on Teensy board */
// PLLCSR &= ~(1 << PINDIV); /* For 8MHz crystal on TeleScience board */
/* Enable the PLL */
PLLCSR |= (1 << PLLE);
while (!(PLLCSR & (1 << PLOCK)))
;
}
int main(void)
{
clock_init();
timer_init();
LEDDDR |= (1 << LEDDDRPIN);
for (;;) {
}
#if 0
while (1) {
LEDPORT |= (1 << LEDOUT);
_delay_ms(1000);
LEDPORT &= ~(1 << LEDOUT);
_delay_ms(1000);
}
#endif
}
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