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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 TEENSY 0
#if TEENSY
#define F_CPU 16000000UL // 16 MHz
#else
#define F_CPU 8000000UL // 8 MHz
#endif
#include <util/delay.h>
#define LEDOUT PORTB7
#define LEDPORT PORTB
#define LEDDDR DDRB
#define LEDDDRPIN DD7
static void
adc_start(void);
ISR(TIMER1_COMPA_vect)
{
adc_start();
}
static void
timer1_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 */
#if TEENSY
OCR1A = 2500; /* 16MHz clock */
#else
OCR1A = 1250; /* 8MHz clock */
#endif
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 */
#if TEENSY
PLLCSR |= (1 << PINDIV); /* For 16MHz crystal on Teensy board */
#else
PLLCSR &= ~(1 << PINDIV); /* For 8MHz crystal on TeleScience board */
#endif
/* Enable the PLL */
PLLCSR |= (1 << PLLE);
while (!(PLLCSR & (1 << PLOCK)))
;
}
static void
timer0_init(void)
{
TCCR0A = ((1 << COM0A1) |
(0 << COM0A0) |
(1 << WGM01) |
(1 << WGM00));
OCR0A = 0x10;
OCR0B = 0;
TIMSK0 = 0;
TCCR0B = ((0 << WGM02) |
(5 << CS00));
}
ISR(ADC_vect)
{
OCR0A = ADCH;
}
static void
adc_start(void)
{
ADMUX = ((0 << REFS1) |
(1 << REFS0) |
(1 << ADLAR) |
(0 << MUX0));
ADCSRB &= ~(1 << MUX5);
ADCSRA = ((1 << ADEN) |
(1 << ADSC) |
(0 << ADATE) |
(1 << ADIE) |
(6 << ADPS0));
}
static void
adc_init(void)
{
ADCSRA = ((1 << ADEN) |
(0 << ADSC) |
(0 << ADATE) |
(1 << ADIE) |
(6 << ADPS0));
ADCSRB = ((0 << ADHSM) |
(0 << MUX5) |
(0 << ADTS0));
DIDR0 |= (1 << 0);
}
int main(void)
{
clock_init();
adc_init();
timer1_init();
timer0_init();
LEDDDR |= (1 << LEDDDRPIN);
for (;;)
;
}
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