/*
 *  spreadspace avr utils
 *
 *
 *  Copyright (C) 2021 Christian Pointner <equinox@spreadspace.org>
 *
 *  This file is part of spreadspace avr utils.
 *
 *  spreadspace avr utils 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, either version 3 of the License, or
 *  any later version.
 *
 *  spreadspace avr utils 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 spreadspace avr utils. If not, see <http://www.gnu.org/licenses/>.
 */

#include <avr/io.h>
#include <avr/interrupt.h>

#include "fan.h"

#define PWM_VAL_MAX 160

void fan_init(void)
{
      // timer for tacho
  DDRD &= ~(1<<PD4);
  PORTD |= (1<<PD4);
  TCCR1B = 0; // make sure timer is stopped

  TCCR1A = 0;
  TCNT1 = 0;
  TIMSK1 = (1<<ICIE1);

  TCCR1B = (1<<CS12); // start timer

      // PWM for speed control
  DDRB |= (1<<PB6);
  TCCR4B = 0; // make sure timer is stopped

  TCCR4A = (1<<COM4B1) | (1<<PWM4B);
  TCCR4D = (1<<WGM40);
  TCNT4 = 0;
  OCR4C = PWM_VAL_MAX;

  OCR4B = PWM_VAL_MAX/2; // set duty cycle to 50:50
  TCCR4B = (1<<CS41); // start timer
}

#define TACHO_DATA_LEN 8
static uint16_t tacho_data[TACHO_DATA_LEN];
static uint8_t tacho_data_idx = 0;
static uint16_t tacho_last_ts = 0;

ISR(TIMER1_CAPT_vect)
{
  uint16_t current = ICR1;
  if(current > tacho_last_ts) {
    tacho_data[tacho_data_idx] = current - tacho_last_ts;
  } else {
    tacho_data[tacho_data_idx] = (UINT16_MAX - tacho_last_ts) + current;
  }
  tacho_last_ts = current;
  tacho_data_idx = (tacho_data_idx >= (TACHO_DATA_LEN-1)) ? 0 : tacho_data_idx+1;
}

uint16_t fan_get_rpm(void)
{
  uint32_t sum = 0;
  cli();
  for(uint8_t i = 0; i < TACHO_DATA_LEN; i++) {
    sum += tacho_data[i];
  }
  sei();

  return (1875000 / (sum / TACHO_DATA_LEN));
}

void fan_speed_set(uint8_t val)
{
  OCR4B = (val > PWM_VAL_MAX) ? PWM_VAL_MAX : val;
}

uint8_t fan_speed_get(void)
{
  return OCR4B;
}

void fan_speed_inc(void)
{
  if(OCR4B < PWM_VAL_MAX)
    OCR4B++;
}

void fan_speed_dec(void)
{
  if(OCR4B > 0)
    OCR4B--;
}