#include <TinyDebug.h>
#undef F_CPU
#define F_CPU 10000000UL

constexpr uint16_t HERTZ {20};

constexpr uint8_t CALC_PSCIDX() {
  return (F_CPU / (1UL * HERTZ)) <= 65535U      ? 0
         : (F_CPU / (2UL * HERTZ)) <= 65535U    ? 1
         : (F_CPU / (4UL * HERTZ)) <= 65535U    ? 2
         : (F_CPU / (8UL * HERTZ)) <= 65535U    ? 3
         : (F_CPU / (16UL * HERTZ)) <= 65535U   ? 4
         : (F_CPU / (64UL * HERTZ)) <= 65535U   ? 5
         : (F_CPU / (256UL * HERTZ)) <= 65535U  ? 6
         : (F_CPU / (1024UL * HERTZ)) <= 65535U ? 7
                                                : 8;
}
constexpr uint16_t PRESCALER[] {1, 2, 4, 8, 16, 64, 256, 1024, 0};
constexpr uint16_t CMPA { F_CPU / (HERTZ * PRESCALER[CALC_PSCIDX()])};

void setCMPA() {
  uint32_t tempperiod {F_CPU / HERTZ};
  uint8_t presc {0};

  while (tempperiod > 65535 && presc < 7) {
    presc++;
    Debug.print(presc); Debug.print(" ");
    tempperiod = tempperiod >> (presc > 4 ? 2 : 1);
    Debug.println(tempperiod);
  }
  Debug.println(tempperiod);
  Debug.println(presc << 1);
  Debug.println(presc);
  // cmpA = tempperiod / 2;
}


void setup() {
  Debug.begin();
  setCMPA();
  Debug.println("----------------");
  Debug.println(CMPA);
  Debug.println(CALC_PSCIDX() << 1);
  Debug.println(CALC_PSCIDX());
}

void loop() {}