1. In the keil:
In the following function is accurate atomic usart.

//add the following code, support the printf function, without the need to select the use MicroLIB
If # 1
# pragma import (__use_no_semihosting)
//the standard library needs the support of function
Struct __FILE
{
Int handle;
};

The FILE __stdout;
//define _sys_exit () to avoid using half a host mode
_sys_exit (int x)
{
X=x;
}
//redefine fputc function
Int fputc (int ch, FILE * f)
{
While ((USART1 - & gt; SR& 0 x40)==0);//cycle to send, until completion of the send
USART1 - & gt; DR=(u8) ch;
return ch;
}
# endif

2. In eclipse:
But I have found in eclipse using the above method is not print, the last use of the solution is the write printf function, the code is as follows:
# include & lt; Stdio. H>
# include & lt; String. H>
# include & lt; Stdarg. H>
Char dat_buf [128].//custom output size
Int printFormat (const char * FMT,... )
{
Int len.
Va_list args.//define the va_list type variable arg
Va_start (args, FMT);//arg initialization, arg is pointing to the first optional parameter
Len=vsprintf (dat_buf, FMT, args);
Va_end (args);
HAL_UART_Transmit (& amp; Huart1 (uint8_t *) dat_buf, len, 0 XFFFF);
Return len.
}
Using direct call the function, use the format consistent with printf,