#include <stdint.h>
#include <stdlib.h>
#include <avr/io.h>
#include <util/delay.h>
#include "ledpwmcurve.h"


#define PWMMin 128
#define PWMMax 1024
#define PWMRange (PWMMax - PWMMin)

#define PWMRandomValue() ((random() % PWMRange) + PWMMin)

#define DelayMin 5
#define DelayMax 50
#define DelayChange 1
#define DelayChangeSteps ((DelayMax - DelayMin) / DelayChange)


void var_delay_ms(int n);



int main()
{
  uint16_t currentValue = PWMRandomValue();
  uint16_t targetValue = currentValue;
  uint16_t startValue = currentValue;

  uint16_t speedUpUntil = currentValue;
  uint16_t slowDownFrom = currentValue;

  uint8_t delay = DelayMax;

  #define goingUp (targetValue > currentValue)


  // -- Set up PWM
  // Set all ports as output (leave none as floating input)
  DDRB = 0b11111111;

  // Set Timer 0 to internal clock, no prescaling.
  // See chapter 11.9 of the ATTiny85 datasheet
  TCCR0B |= (1 << CS00);

  // Set to 'Fast PWM' mode
  TCCR0A |= (1 << WGM01) | (1 << WGM00);

  // Clear OC0B output on compare match, upwards counting
  TCCR0A |= (1 << COM0B1);


  while (1)
  {
    if (targetValue == currentValue)
    {
      do
      {
        targetValue = PWMRandomValue();
      } while (targetValue == currentValue);

      startValue = currentValue;
      speedUpUntil = goingUp ? startValue + DelayChangeSteps : startValue - DelayChangeSteps;
      slowDownFrom = goingUp ? targetValue - DelayChangeSteps : targetValue + DelayChangeSteps;
    }


    if (goingUp)
    {
      currentValue++;

      if (currentValue < speedUpUntil)
        delay -= DelayChange;
      else if (currentValue > slowDownFrom)
        delay += DelayChange;
      else
        delay = DelayMin;
    }
    else
    {
      currentValue--;

      if (currentValue > speedUpUntil)
        delay -= DelayChange;
      else if (currentValue < slowDownFrom)
        delay += DelayChange;
      else
        delay = DelayMin;
    }


    // Update PWM value
    OCR0B = antilog(currentValue);
    var_delay_ms(delay);
  }

  return 0;
}


// Source: http://www.avrfreaks.net/forum/how-use-delay-variable
void var_delay_ms(int n)
{
  while(n--)
    _delay_ms(1);
}