/*

 -= Chaos Synth Karplus =-

 Based Logistic equation

 Pot0 = chaos constant
 Pot1 = lowpass filter
 Pot2 = tempo/speed

 PWM audio out - PIN 3

 created by JLS 2018

 */

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

#define SIZE 1024
#define OFFSET 128

uint8_t out = 0;
int last = 0;
int curr = 0;
uint8_t delaymem[SIZE];
uint8_t locat = 0;
uint8_t bound = SIZE;
int accum = 0;
int lowpass = 1;

float r;
float x = 0.2;


#define PWM_PIN       3
#define PWM_VALUE_DESTINATION     OCR2B
#define PWM_INTERRUPT TIMER2_OVF_vect

void initializeTimer() {

  TCCR2A = _BV(COM2B1) | _BV(WGM20);
  TCCR2B = _BV(CS20);
  TIMSK2 = _BV(TOIE2);

  pinMode(PWM_PIN,OUTPUT);
  
}


SIGNAL(PWM_INTERRUPT)
{
   
  PWM_VALUE_DESTINATION = out;

  delaymem[locat++] = out;

  if (locat >= bound) locat = 0;
    
  curr = delaymem[locat];
    
  out = accum >> lowpass;
    
  accum = accum - out + ((last>>1) + (curr>>1));

  last = curr;

}

void setup()
{  
 
  initializeTimer();
 
 }

void loop() {
  
  r = map(analogRead(0),0,1023,35000,39900);
  r /= 10000.0;
  
  float nx = x;
  x = r*nx*(1-nx);
  
  uint8_t xout = (SIZE-OFFSET) * x;          

  for (int i = 0; i < SIZE; i++) delaymem[i] = random(256);
   
  lowpass =  analogRead(1)>>8;

  bound = OFFSET + xout;
  
  delay (analogRead(2)>>2);

}