#define PWM_CT1_A   9 //OC1A
#define PWM_CT1_B  10 //OC1B


#define maxpwm 250
#define minpause 256

uint16_t pwm = 32;
uint16_t pause = 256;

void ct1_init()
{
  pinMode(PWM_CT1_B,OUTPUT);
  // 64 khz
  TCCR1A = (1 << COM1B1)|(1 << WGM11);  //fast PWM 
  TCCR1B = (1 << CS10)|(1 << WGM13)|(1 << WGM12);       // prescaler 0
  OCR1B = pwm;                          // pwm value  
  ICR1  = pause;                        // max value  
}

void setup() 
{
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(115200);
  ct1_init();
}

char in_ch;

void loop() 
{ 
  if (Serial.available())
  {
    in_ch = Serial.read();
    if (in_ch == '1') pwm = constrain(pwm+8,0,maxpwm);
    if (in_ch == '2') pwm = constrain(pwm-8,0,maxpwm);
    if (in_ch == '3') pause = constrain(pause+8,minpause,0xFFFF);
    if (in_ch == '4') pause = constrain(pause-8,minpause,0xFFFF);
    OCR1B = pwm;
    ICR1  = pause;  
    Serial.print(pwm);
    Serial.print("  ");
    Serial.println(pause);
  }
  delay(100);
}