#include "stm32f4_discovery.h"

void RCC_Config(void)
{
uint32_t           PLL_M;      
  uint32_t           PLL_N;
  uint32_t           PLL_P;
  uint32_t           PLL_Q;
  RCC_DeInit();
RCC_HSEConfig(RCC_HSE_ON);
while(RCC_WaitForHSEStartUp()!=SUCCESS);
PLL_M =8;
  PLL_N =336;
PLL_P = 2;
PLL_Q=7;
RCC_PLLConfig(RCC_PLLSource_HSE,PLL_M,PLL_N, PLL_P,PLL_Q);
RCC_PLLCmd(ENABLE);
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
RCC_HCLKConfig(RCC_HCLK_Div1);
RCC_PCLK1Config(RCC_HCLK_Div1);
RCC_PCLK2Config(RCC_HCLK_Div2);


}


void USART_Config(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStruct;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB,ENABLE);


GPIO_PinAFConfig(GPIOB,GPIO_PinSource6,GPIO_AF_USART1);//配置PB6，PB7位串口
GPIO_PinAFConfig(GPIOB,GPIO_PinSource7,GPIO_AF_USART1);

GPIO_InitStructure.GPIO_Pin=GPIO_Pin_6;
GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType=GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_UP;
GPIO_Init(GPIOB,&GPIO_InitStructure);


GPIO_InitStructure.GPIO_Pin=GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType=GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_UP;
GPIO_Init(GPIOB,&GPIO_InitStructure);

USART_InitStructure.USART_BaudRate=9600;
USART_InitStructure.USART_HardwareFlowControl=USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode=USART_Mode_Rx|USART_Mode_Tx;
USART_InitStructure.USART_Parity=USART_Parity_No;
USART_InitStructure.USART_StopBits=USART_StopBits_1;
USART_InitStructure.USART_WordLength=USART_WordLength_8b;

USART_Init(USART1,&USART_InitStructure);
USART_Cmd(USART1,ENABLE);

USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);

NVIC_InitStruct.NVIC_IRQChannel=USART1_IRQn;
NVIC_InitStruct.NVIC_IRQChannelCmd=ENABLE;
NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority=1;
NVIC_InitStruct.NVIC_IRQChannelSubPriority=1;

NVIC_Init(&NVIC_InitStruct);

}


void USART1_IRQHandler(void)
{
u8 res;

if(USART_GetITStatus(USART1,USART_IT_RXNE)!= RESET）//下位机接收到什么数据，就把这个数据重新发送给串口助手
{
   res=USART_ReceiveData(USART1);
   USART_SendData(USART1,res);

}

}


int main(void)
{

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

RCC_Config();
USART_Config();
while(1);

}


以下是串口助手的调试结果：



本该是串口助手发送什么就能回接到同样的数据，结果发送和接收的不一样，哪位大神能帮忙看看。