一个小小的串口居然让我捣鼓了两天还没出来，时钟正确，usart寄存器值也是对的。然后试了试源码居然一样乱码。不知道是怎么了。板子是官方的论坛送的stm32f429zit6。下面贴上代码和源码。
#include "stm32f4xx_usart.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_flash.h"
#include "stm32f4xx_pwr.h"
#include "stm32f4xx_exti.h"
#include "misc.h"
#include
#include
#include
void USART_GPIO_Config(void);
void USART_Config(void);
void USART_SendString(char *str);
void RCC_Config(void);
void uart3_init(void);
int main(void)
{
 SystemInit();
 uart3_init();
 //USART_GPIO_Config();
 USART_Config();
 USART_SendData(USART3, '9');
 while (USART_GetFlagStatus(USART3, USART_FLAG_TC) == RESET)
       {}
    while(1)
    {
     USART_SendData(USART3, 'a');
     while (USART_GetFlagStatus(USART3, USART_FLAG_TC) == RESET)
       {}
     //USART_SendString("hello world\r");
     //Array[num++] = USART_ReceiveData(USART1);
     //printf("hello world/r");
    }
}
void uart3_init(void)
{
  USART_InitTypeDef USART_InitStructure;
  GPIO_InitTypeDef GPIO_InitStructure;
  /* Enable GPIO clock */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
  /* Enable USART clock */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
  /* Connect USART pins to AF7 */
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_USART3);
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_USART3);
  /* Configure USART Tx and Rx as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = 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(GPIOC, &GPIO_InitStructure);
   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
     GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
     GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
     GPIO_Init(GPIOC, &GPIO_InitStructure);
}
void USART_SendString(char *str)
{
 while(*str!=0)
 {
  while(RESET == USART_GetFlagStatus(USART1,USART_FLAG_TXE));
     USART_SendData(USART1, *str++);
 }
}

void USART_Config(void)
{
 USART_InitTypeDef USART_InitStructure;
 NVIC_InitTypeDef NVIC_InitStructure;

 RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
 USART_InitStructure.USART_BaudRate = 9600;
    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_Tx | USART_Mode_Rx;
 USART_Init(USART3, &USART_InitStructure);

   /* NVIC configuration */
   /* Configure the Priority Group to 2 bits */
   NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
   /* Enable the USARTx Interrupt */
   NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
   NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
   NVIC_Init(&NVIC_InitStructure);
   USART_ITConfig(USART1, USART_IT_TXE|USART_IT_RXNE, ENABLE);
    //USART_ITConfig(USART1,USART_IT_CTS, DISABLE);
    USART_Cmd(USART3, ENABLE);
}

void uart_init(u32 pclk2,u32 bound)
{
 float temp;
 u16 mantissa;
 u16 fraction;
 temp=(float)(pclk2*1000000)/(bound*16);
 mantissa=temp;
 fraction=(temp-mantissa)*16;
    mantissa