一直在用，没出现过问题
```c
/*-----------------------------------------------------------*/
void rt_hw_console_output(const char *str)
{
//#error "TODO 3: Output the string 'str' through the uart."
	rt_size_t i = 0, size = 0;
	size = rt_strlen(str);
	for (i = 0; i < size; i++)
	{
			if (*(str + i) == '\n')
			{
				 break;
			}
	}
	SEGGER_RTT_printf(0,"%s",str);
}

char rt_hw_console_getchar(void)
{ 
	int ch = 0;
    char tempbuffer[2];
    uint8_t NumBytes=0;

NumBytes = SEGGER_RTT_Read(0, &tempbuffer[0], 1);
    if(NumBytes==1)
    {
        ch=tempbuffer[0];
    }
    return ch;
}

/*-----------------------------------------------------------*/
/* support printf function, usemicrolib is unnecessary */
#if (__ARMCC_VERSION > 6000000)
  __asm (".global __use_no_semihosting\n\t");
  void _sys_exit(int x)
  {
    x = x;
  }
  /* __use_no_semihosting was requested, but _ttywrch was */
  void _ttywrch(int ch)
  {
    ch = ch;
  }
  FILE __stdout;
#else
 #ifdef __CC_ARM
  #pragma import(__use_no_semihosting)
  struct __FILE
  {
    int handle;
  };
  FILE __stdout;
  void _sys_exit(int x)
  {
    x = x;
  }
  /* __use_no_semihosting was requested, but _ttywrch was */
  void _ttywrch(int ch)
  {
    ch = ch;
  }
 #endif
#endif

#if defined (__GNUC__) && !defined (__clang__)
  #define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
  #define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif

#if defined (__GNUC__) && !defined (__clang__)
int _write(int fd, char *pbuffer, int size)
{
  for(int i = 0; i < size; i ++)
  {
    __io_putchar(*pbuffer++);
  }

return size;
}
#endif
	
/**
  * @brief  retargets the c library printf function to the usart.
  * @param  none
  * @retval none
  */
PUTCHAR_PROTOTYPE
{
  SEGGER_RTT_PutChar(0, ch);    //adapter	
	return ch;
}
```