#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/power.h>
#include <util/delay.h>
#include <util/atomic.h>

#include "lights.h"

/*
 * Single PWM channel on OC1B (pin PB4 of Tiny45).
 * Counts from 0 to 0xFF, without OCR1C compare.
 */

volatile unsigned char pwm_enabled;

static void inline enable_pll()
{
	/* Async clock */
	PLLCSR = _BV(PLLE) | _BV(LSM);

	/* Synchronize to the phase lock */
	_delay_us(100);
	while ((PLLCSR & _BV(PLOCK)) == 0)
		;
	PLLCSR |= _BV(PCKE);
}

void init_pwm()
{
	pwm_enabled = 0;
	power_timer1_enable();

	TCCR1 = _BV(CTC1) | _BV(CS11);	// pll_clk/2
	GTCCR = _BV(COM1B1) | _BV(PWM1B);

	OCR1C = PWM_MAX;
	OCR1B = 0;		// initial stride is 0

	DDRB &= ~(_BV( PB4 ));
	PORTB &= ~_BV(PB4); // set to zero
}

void susp_pwm()
{
	DDRB &= ~(_BV( PB4 ));
	PORTB &= ~(_BV( PB4 ));
	TCCR1 = 0;
	TIMSK = 0;
	TIFR = 0;

	PLLCSR &= ~(_BV(PLLE) | _BV(PCKE));
}

void pwm_off()
{
	OCR1B = 0;
	DDRB &= ~_BV(PB4);

	PLLCSR &= ~(_BV(PLLE) | _BV(PCKE));
	power_timer1_disable();
	pwm_enabled = 0;
}

void pwm_set(uint8_t stride)
{
	OCR1B = stride;

	if (!pwm_enabled) {
		power_timer1_enable();
		enable_pll();
		DDRB |= _BV(PB4);
		pwm_enabled = 1;
	}
}