我有一段代码如下，想使用串口2进行通信，奇怪的是只有先初始化串口1，然后再初始化串口2，串口2才能工作，如果单独调用串口2的初始化代码，串口2就工作不了。不知道是不是哪段代码用错了？谢谢！
#if 1
#pragma import(__use_no_semihosting)                   
struct __FILE 
{ 
int handle; 
}; 

FILE __stdout;       

int fputc(int ch, FILE *f)
{
while((USART2->SR&0X40)==0);//???··???,?±??·????ê±?   
USART2->DR = (u8) ch;      
return ch;
}
#endif
 
void uart1_init(u32 bound){
  GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_AHB1Periph_GPIOA,ENABLE); 
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);


GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_USART1); 
GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_USART1); 


  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; 
GPIO_Init(GPIOA,&GPIO_InitStructure); 


USART_InitStructure.USART_BaudRate = bound;
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(USART1, &USART_InitStructure); 

  USART_Cmd(USART1, ENABLE); 

USART_ClearFlag(USART1, USART_FLAG_TC);



USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);//?????à??????

//Usart1 NVIC ????
  NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;//?®??1?????¨??
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3;//??????????3
NVIC_InitStructure.NVIC_IRQChannelSubPriority =3; //×???????3
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ?¨??????
NVIC_Init(&NVIC_InitStructure); //?ù?????¨????????????VIC?????÷??



}
void uart_init(u32 bound){
GPIO_InitTypeDef GPIO_InitStructure;
  USART_InitTypeDef USART_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB2PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2,ENABLE);


GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3; //GPIOA9??GPIOA10
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;//????????
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //????50MHz
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; //???ì????????
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; //????
GPIO_Init(GPIOA,&GPIO_InitStructure); //??????PA9??PA10

//?®??1????????????????
GPIO_PinAFConfig(GPIOA,GPIO_PinSource2,GPIO_AF_USART2); //GPIOA2??????USART2
GPIO_PinAFConfig(GPIOA,GPIO_PinSource3,GPIO_AF_USART2); //GPIOA3??????USART2

USART_InitStructure.USART_BaudRate = bound;
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(USART2, &USART_InitStructure); 
  
NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn; 
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; 
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2; 
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; 
NVIC_Init(&NVIC_InitStructure); 
 
USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);
   
USART_Cmd(USART2, ENABLE); 

}