terom@47: #include <avr/io.h>
terom@49: #include "stdlib.h"
terom@47: 
terom@49: #include <avr/interrupt.h>
terom@47: 
terom@49: #define TIMER_FLAGS     GPIOR0
terom@49: #define TIMER1_BUSY     1
terom@49: 
terom@49: /*
terom@49:  * Setup timers.
terom@49:  */
terom@49: void timer_init (void)
terom@49: {
terom@49:     TCCR1A = (
terom@49:             // OC1A output pin disconnected
terom@49:             0b00 << COM1A0
terom@49:             // OC1B output pin disconnected
terom@49:         |   0b00 << COM1B0
terom@49:             // no PWM
terom@49:         |   0b00 << WGM10
terom@49:     );
terom@49:     TCCR1B = (
terom@49:             // CTC mode
terom@49:             0b01 << WGM12 
terom@49:     );
terom@49:     TCCR1C = 0;
terom@49: }
terom@49: 
terom@49: void timer1_start (short cycles)
terom@49: {
terom@49:     // count up from zero...
terom@49:     TCNT1 = 0;
terom@49: 
terom@49:     // ...to the given number of timer cycles
terom@49:     OCR1A = cycles;
terom@49: 
terom@49:     // start!
terom@49:     sbi(&TIMER_FLAGS, TIMER1_BUSY);
terom@49:     TIMSK1 = (
terom@49:             // OCA interrupt
terom@49:             0b1 << OCIE1A       // enable
terom@49:     );
terom@49:     TCCR1B = (
terom@49:             // WGM
terom@49:             0b01  << WGM12      // CTC
terom@49: 
terom@49:             // clocksource
terom@49:         |   0b101 << CS10       // 1024'th
terom@49:     );
terom@49: }
terom@49: 
terom@49: static void timer1_stop ()
terom@49: {
terom@49:     // WGM: normal
terom@49:     // clocksource: stop
terom@49:     TCCR1B = 0;
terom@49: 
terom@49:     cbi(&TIMER_FLAGS, TIMER1_BUSY);
terom@49: }
terom@49: 
terom@49: ISR(TIMER1_COMPA_vect)
terom@49: {
terom@49:     timer1_stop();
terom@49: 
terom@49:     // XXX: cpu will automatically wake up from sleep()
terom@49: }
terom@49: 
terom@49: /*
terom@49:  * Sleep on timer1 interrupt.
terom@49:  */
terom@49: void timer_sleep (int cycles)
terom@49: {
terom@49:     // set timer
terom@49:     timer1_start(cycles);
terom@49: 
terom@49:     // sleep
terom@49:     // TODO: PRR
terom@49:     SMCR = (
terom@49:             // idle sleep
terom@49:             (0b00 << SM0)
terom@49: 
terom@49:             // enable sleep
terom@49:         |   (0b1 << SE)
terom@49:     );
terom@49:     
terom@49:     // sleep
terom@49:     while (tbi(&TIMER_FLAGS, TIMER1_BUSY)) {
terom@49:         __asm__ ( "sleep" :: );
terom@49:     }
terom@49: 
terom@49:     // cleanup
terom@49:     SMCR = 0;
terom@49: }
terom@47: 
terom@47: int main (void)
terom@47: {
terom@49:     timer_init();
terom@49: 
terom@47:     // LED
terom@49:     sbi(&DDRB, DDB5);
terom@49: 
terom@49:     sei();
terom@49: 
terom@49:     // blink
terom@49:     short timeout = 1000;
terom@49:     short delta = 10;
terom@47: 
terom@47:     while (true) {
terom@49:         // bitflip
terom@49:         xbi(&PORTB, PORTB5);
terom@47:         
terom@49:         timer_sleep(timeout);
terom@49:         
terom@49:         timeout += delta;
terom@47:     }
terom@47: }