OC3A is on pin D6~ for 32 pins mcus

[trimarco232]

says we want to use PD1 (pin n°31) as TXD of the USART : OC3A is no more available as PWM output for this pin
but we need 8 PWM outputs
the solution might be (I didn't test it yet) :

1. at pin D6~ , output OC3A :
   EDIT : don't set PD6 as OUTPUT !
   PMX1 Bit 2 C3AC = 1 = OC3A output to QFP48/AC0P
2. at pin A0 (PC0) , use OC0A* output :
   PMX0 Bit 3 C0AC0 : OC0A Auxiliary output control
   The 0C0A output is controlled by the C0AC0 bit in conjunction with the C0AS bit of the TCCR0B register:
   { C0AC0, C0AS } = 10 = 0C0A output to PC0
   in this case , one probably don't have to worry about the OC0AS Bit of TCCR0B ...

[h4tr3d]

Hmmm.... interesting. 8 PWM and HW USART at time...

For now I disable using USART and enable OC3A on the D1/TXD pin. Just turn off USART and route internal PortF output:

        DDRD &= ~(1u << DDD1);
        DDRF |= (1u << DDF1);

complete sample for PWM configuration on the Timer3A/B outputs (my case):

    // 16 bit
    case Pwm::Timer3A:
    case Pwm::Timer3B:
    {
      // COM1Ax, COM1Bx - control output enabled
      // 1 - active high (ex COM1A1)
      // 0 - active low  (ex COM1A0)
      uint8_t output = TCCR3A & ((1u << COM3A1) | (1u << COM3B1));

      if (id == Pwm::Timer3A)
        output |= (1u << COM3A1);
      else
        output |= (1u << COM3B1);

      TCNT3 = 0;
      TCCR3A = 0;
      TCCR3C = 0;
      byte n = 1;
      // clksys / 1 = 1
      // clksys / 8 = 2
      // clksys / 64 = 3
      // clksys / 256 = 4
      // clksys / 1024 = 5
      // [CS12:CS10]
#if 1
      // 8 bit mode
      TCCR3A = output | (1 << WGM30);
      TCCR3B = (1 << WGM32) | n;
      ICR3 = 255;
#else
      // 16 bit
      TCCR3A = output | (1 << WGM31);
      TCCR3B = (1 << WGM33) | (1 << WGM32) | n;
      ICR3 = 65535;
#endif
      // Turn off shared functions
      // Ref: https://github.com/dbuezas/lgt8fx/issues/57#issuecomment-758955088
      // Ref: https://github.com/dbuezas/lgt8fx/issues/57#issuecomment-759052620 - repair on breaks
      if (id == Pwm::Timer3A) {
        DDRD &= ~(1u << DDD1);
        DDRF |= (1u << DDF1);

        // set bit2 to 0 - route OC3A to PF1 that internally connected with PD1
        //PMX1 &= ~(1u << C3AC);

      } else {
        DDRD &= ~(1u << DDD2);
        DDRF |= (1u << DDF2);
      }

      if (id == Pwm::Timer3A)
        OCR3A = val;
      else
        OCR3B = val;

      break;
    }

I also use Timer0 with Divider 1, so some functions like millis() "breaks". I just use next WA:

constexpr unsigned long long int ms(unsigned long long int val) {
  return val * 64;
}
constexpr unsigned long long int operator""_ms(unsigned long long int val) {
  return val * 64; // we use divider 1 vs default divider 64 for timer0
}

and in the code:

static auto last_tm = millis();
if (millis() - last_tm > 100_ms) { // or ms(100)
  // do some work
  last_tm = millis();
}

[trimarco232]

ok , thanks !
please take care that the signal AC0P/OC3A and the signal PD6/TXD*/OC0A share the same pin , on 32 and 20 pins devices
so if you use OC3A on this pin , don't set PD6 as OUTPUT !
if you configure the output stage of OC3A , the signal will automatically be an output

[h4tr3d]

Don't enable Serial too :-) My board was not damaged, but too overheated.