/*
*/


#define PWM_CT2A   11 //OC2A
#define PWM_CT2B    3 //OC2B

#define maxpwm 120

void ct2_init()
{
  pinMode(PWM_CT2A, OUTPUT);
  pinMode(PWM_CT2B, OUTPUT);

  TCCR2A = (1 << COM2B1) |(1 << COM2B0) | (1 << COM2A1) | (1 << WGM20);  
  TCCR2B = (1 << CS20);      // prescaler 0
  OCR2A = 0;                               
  OCR2B = 255;               // pwm value  
}


void setup() 
{
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(115200);

  ct2_init();
}

void setct(uint8_t data)
{
  uint8_t ld = constrain(data,0,maxpwm);
  OCR2A = ld;                               
  OCR2B = 255-ld;                           // pwm value   
  
}

uint8_t ct,i;

uint8_t sintab10[11] ={0,39,75,103,121,127,121,103,75,39,0};

// 50ns resonance = 20mhz. 

void loop() 
{ 
  
  for (i=0;i<11;i++) 
  {
    uint8_t h;
    //delay(1);
    delayMicroseconds(900);
    h = sintab10[i];
    ct = h/2; // + h/4 + h/8;
    setct(ct);
  }
  
  /*
  if (Serial.available())
  {
    int inp;
    inp = Serial.read();
    Serial.println(inp);
    if (inp == 49) ct+=10;
    if (inp == 50) ct-=10;
    Serial.println(ct);
  }
  setct(ct);
  delay(100);
  */
  
  
}