GOTO in hardware serial? Please review alternative code

[robtillaart]

I found a goto in HardwareSerial.cpp (IDE 1.0.3)

Code: [Select]


void HardwareSerial::begin(unsigned long baud)
{
  uint16_t baud_setting;
  bool use_u2x = true;

#if F_CPU == 16000000UL
  // hardcoded exception for compatibility with the bootloader shipped
  // with the Duemilanove and previous boards and the firmware on the 8U2
  // on the Uno and Mega 2560.
  if (baud == 57600) {
    use_u2x = false;
  }
#endif

[color=red]try_again:[/color]
 
  if (use_u2x) {
    *_ucsra = 1 << _u2x;
    baud_setting = (F_CPU / 4 / baud - 1) / 2;
  } else {
    *_ucsra = 0;
    baud_setting = (F_CPU / 8 / baud - 1) / 2;
  }
 
  if ((baud_setting > 4095) && use_u2x)
  {
    use_u2x = false;
    goto try_again;  // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
  }

  // assign the baud_setting, a.k.a. ubbr (USART Baud Rate Register)
  *_ubrrh = baud_setting >> 8;
  *_ubrrl = baud_setting;

  transmitting = false;

  sbi(*_ucsrb, _rxen);
  sbi(*_ucsrb, _txen);
  sbi(*_ucsrb, _rxcie);
  cbi(*_ucsrb, _udrie);
}


This should be replaced by a goto less version - refactored the logic too - please review

Code: [Select]



void HardwareSerial::begin(unsigned long baud)
{
  *_ucsra = 1 << _u2x;
  uint16_t baud_setting = (F_CPU / 4 / baud - 1) / 2;

  // includes hardcoded exception for compatibility with the bootloader shipped
  // with the Duemilanove and previous boards and the firmware on the 8U2
  // on the Uno and Mega 2560.
  if (((F_CPU == 16000000UL) && (baud == 57600)) || (baud_setting >4095))
  {
    *_ucsra = 0;
    baud_setting = (F_CPU / 8 / baud - 1) / 2;
  }

  // assign the baud_setting, a.k.a. ubbr (USART Baud Rate Register)
  *_ubrrh = baud_setting >> 8;
  *_ubrrl = baud_setting;

  transmitting = false;

  sbi(*_ucsrb, _rxen);
  sbi(*_ucsrb, _txen);
  sbi(*_ucsrb, _rxcie);
  cbi(*_ucsrb, _udrie);
}

same patch can be done for - void HardwareSerial::begin(unsigned long baud, byte config) - too

I will post this a change request for this

[robtillaart]

Submitted here - https://github.com/arduino/Arduino/issues/1262 -

A "Hello World" sketch on a 16MHZ UNO works on 9600, 57600 and 115200 baud. Test different code paths.