STM32工程中调用printf函数

在STM32工程中调用printf函数，需要加入如下代码：

#ifdef __GNUC__
/* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printf
set to 'Yes') calls __io_putchar() */
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif /* __GNUC__ UT*/
void Printf_Init(void)
{
/*!< At this stage the microcontroller clock setting is already configured,
this is done through SystemInit() function which is called from startup
file (startup_stm32f10x_xx.s) before to branch to application main.
To reconfigure the default setting of SystemInit() function, refer to
system_stm32f10x.c file
*/
/* USARTx configured as follow:
- BaudRate = 115200 baud
- Word Length = 8 Bits
- One Stop Bit
- No parity
- Hardware flow control disabled (RTS and CTS signals)
- Receive and transmit enabled
*/
USART_InitStructure.USART_BaudRate = 115200;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
STM_EVAL_COMInit(COM1, &USART_InitStructure);
/* Output a message on Hyperterminal using printf function */
//printf("\n\rUSART Printf Example: retarget the C library printf function to the USART\n\r");
// printf("\r\n\n\n WWW.ARMJISHU.COM %s configured....", EVAL_COM1_STR);
// printf("\n\r ############ WWW.ARMJISHU.COM! ############ ("__DATE__ " - " __TIME__ ")\n\r");
}
/**
* @brief Retargets the C library printf function to the USART.
* @param None
* @retval None
*/
PUTCHAR_PROTOTYPE
{
/* Place your implementation of fputc here */
/* e.g. write a character to the USART */
USART_SendData(EVAL_COM1, (uint8_t) ch);
/* Loop until the end of transmission */
while (USART_GetFlagStatus(EVAL_COM1, USART_FLAG_TC) == RESET)
{}
return ch;
}