当通过printf()处理信息，如何知道哪一UART传输数据？

#include "stm32f4xx.h"

#include "printf.h"



void Printf_Configuration(void)

{

                GPIO_InitTypeDef GPIO_InitStructure;

                USART_InitTypeDef USART_InitStructure; 

        

                //PB6->TX  PB7->Rx

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11;

    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

    GPIO_Init(GPIOC, &GPIO_InitStructure);

    

    GPIO_PinAFConfig(GPIOC,GPIO_PinSource10,GPIO_AF_UART4);

    GPIO_PinAFConfig(GPIOC,GPIO_PinSource11,GPIO_AF_UART4);

        

                USART_InitStructure.USART_BaudRate = 19200;

    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;

    USART_Init(UART4,&USART_InitStructure);   

    USART_ITConfig(UART4,USART_IT_RXNE,ENABLE);

    USART_Cmd(UART4,ENABLE);

}



int fputc(int ch, FILE *f)

{        

                while (USART_GetFlagStatus(UART4, USART_FLAG_TC) == RESET);

                USART_SendData(UART4, (uint8_t) ch);

                while (USART_GetFlagStatus(UART4, USART_FLAG_TC) == RESET);

                return ch;

}



int fgetc(FILE *f) 

{

    int ch;

    while (USART_GetFlagStatus(UART4, USART_FLAG_RXNE) == RESET);

    ch = USART_ReceiveData(UART4);

    while (USART_GetFlagStatus(UART4, USART_FLAG_TC) == RESET);

    USART_SendData(UART4, (uint8_t) ch);

    return ch;

}

#ifndef __PRINTF_H__

#define __PRINTF_H__



#include <stdio.h>



void Printf_Configuration(void);



#endif