请教高手，为什么我用STM32F4 串口发送数据，管脚无波形，仿真时看到DR一直无数据，发送标志位一直为0，跪求高手解释！！配置如下：

只看该作者 · 2018-8-1 18:40

void USART2_Parameter_Configuration(u16 baudrate,u16 USART_StopBits,u16 USART_Parity)
{
u16 temp_wordlength;
USART_InitTypeDef USART_InitStructure;
USART_ClockInitTypeDef  USART_ClockInitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;

RCC_APB2PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG,ENABLE);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource3,GPIO_AF_USART2);  //复合管脚
GPIO_PinAFConfig(GPIOA, GPIO_PinSource2,GPIO_AF_USART2);  //复合管脚
//USART2 CAM_RX
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP ;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOA, &GPIO_InitStructure);

//USART2 CAM_TX
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; //设置输入
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; //推挽
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; //上拉
GPIO_Init(GPIOA, &GPIO_InitStructure);
if(USART_Parity)
{
  temp_wordlength=USART_WordLength_9b;
}
else
{
  temp_wordlength=USART_WordLength_8b;
}
USART_InitStructure.USART_BaudRate = baudrate;
USART_InitStructure.USART_WordLength = temp_wordlength;
USART_InitStructure.USART_StopBits =USART_StopBits;
USART_InitStructure.USART_Parity =USART_Parity;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
/* Configure USART2 */
USART_Init(USART2,&USART_InitStructure);
// USART_ClockInitStructure.USART_Clock = USART_Clock_Disable;
// USART_ClockInitStructure.USART_CPOL = USART_CPOL_Low;
// USART_ClockInitStructure.USART_CPHA = USART_CPHA_2Edge;
// USART_ClockInitStructure.USART_LastBit = USART_LastBit_Disable;
USART_ClockStructInit(&USART_ClockInitStructure);
USART_ClockInit(USART2,&USART_ClockInitStructure);

//中断
// NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 7;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);

  /* Enable USART3 Receive and Transmit interrupts */
  //USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);
  //USART_ITConfig(USART2, USART_IT_TXE, ENABLE);

/* Enable the USART2 */
USART_Cmd(USART2, ENABLE);

}

请教高手，为什么我用STM32F4 串口发送数据，管脚无波形，仿真时看到DR一直无数据，发送标志位一直为0，跪求高手解释！！配置如下：

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