stm32用485通信的问题，显示字符，搞了一星期了，希望大家帮忙

ellishu

目的就是在超级终端上面显示字符，一用printf就出错，大家帮我看看哪里错了吧？谢谢了
（）——其中PA2控制485线通信，用的usart3
/******************** (C) COPYRIGHT 2007 STMicroelectronics ********************
* File Name          : main.c
* Author             : MCD Application Team
* Version            : V1.0
* Date               : 10/08/2007
* Description        : Main program body
********************************************************************************
* THE PRESENT SOFTWARE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS
* WITH CODING INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE TIME.
* AS A RESULT, STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY DIRECT,
* INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING FROM THE
* CONTENT OF SUCH SOFTWARE AND/OR THE USE MADE BY CUSTOMERS OF THE CODING
* INFORMATION CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS.
*******************************************************************************/
/* Includes ------------------------------------------------------------------*/
 /* Includes ------------------------------------------------------------------*/
#include "stm32f10x_lib.h"
#include "stdio.h"
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#define TxBufferSize   (countof(TxBuffer) - 1)
#define countof(a)   (sizeof(a) / sizeof(*(a)))
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
USART_InitTypeDef USART_InitStructure;
ErrorStatus HSEStartUpStatus;
/* Private function prototypes -----------------------------------------------*/
void RCC_Configuration(void);
void GPIO_Configuration(void);
void NVIC_Configuration(void);
u8 TxBuffer[]="\r\n Success of displaying  \r\n";
u8 TxCounter=0;
u8 NbrOfDataToTransfer=TxBufferSize;

#ifdef __GNUC__
  /* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printf
     set to 'Yes') calls __io_putchar() */
  #define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
  #define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif /* __GNUC__ */
 
/* Private functions ---------------------------------------------------------*/
/*******************************************************************************
* Function Name  : main
* Description    : Main program
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
int main(void)
{
#ifdef DEBUG
  debug();
#endif
  /* System Clocks Configuration */
  RCC_Configuration();
      
  /* NVIC configuration */
  NVIC_Configuration();
  /* Configure the GPIO ports */
  GPIO_Configuration();
/* USARTx configuration ------------------------------------------------------*/
  /* USARTx configured as follow:
        - BaudRate = 115200 baud 
        - Word Length = 8 Bits
        - One Stop Bit
        - No parity
        - Hardware flow control disabled (RTS and CTS signals)
        - Receive and transmit enabled
        - USART Clock disabled
        - USART CPOL: Clock is active low
        - USART CPHA: Data is captured on the second edge
        - USART LastBit: The clock pulse of the last data bit is not output to
                         the SCLK pin
  */
  USART_InitStructure.USART_BaudRate = 115200;
  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_InitStructure.USART_Clock = USART_Clock_Disable;
  USART_InitStructure.USART_CPOL = USART_CPOL_Low;
  USART_InitStructure.USART_CPHA = USART_CPHA_2Edge;
  USART_InitStructure.USART_LastBit = USART_LastBit_Disable;
 
  /* Configure the USARTx */
  USART_Init(USART3, &USART_InitStructure);
  /* Enable the USARTx */
  USART_Cmd(USART3, ENABLE);
 
// while(NbrOfDataToTransfer--)
//
//  {
//   GPIOA->ODR |=0x00000004; // 使能发信号
// USART_SendData(USART3,TxBuffer[TxCounter++]);
// while(USART_GetFlagStatus(USART3, USART_FLAG_TC) == RESET);
// //printf("\r\n Success of displaying  \r\n"); ////
//   }
当把下面两句话改成上面几段文字的时候就可以用了，超级终端就显示了字符。不知道为什么啊？

  GPIOA->ODR |=0x00000004; // 使能发信号
 printf("\r\n Success of displaying  \r\n"); ////
 

  while (1)
  {
  }
}
/*******************************************************************************
* Function Name  : 重定义系统putchar函数int fputc(int ch, FILE *f)
* Description    : 串口发一个字节
* Input          : int ch, FILE *f
* Output         :
* Return         : int ch
*******************************************************************************/
//int fputc(int ch, FILE *f)
//{
//    //USART_SendData(USART3, (u8) ch);
//    USART3->DR = (u8) ch;
//   
//    /* Loop until the end of transmission */
//    while(USART_GetFlagStatus(USART3, USART_FLAG_TXE) == RESET)
//    {
//    }
//
//    return ch;
//}
/*******************************************************************************
* Function Name  : RCC_Configuration
* Description    : Configures the different system clocks.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
void RCC_Configuration(void)
{
  /* RCC system reset(for debug purpose) */
  RCC_DeInit();
  /* Enable HSE */
  RCC_HSEConfig(RCC_HSE_ON);
  /* Wait till HSE is ready */
  HSEStartUpStatus = RCC_WaitForHSEStartUp();
  if(HSEStartUpStatus == SUCCESS)
  {
    /* Enable Prefetch Buffer */
    FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
    /* Flash 2 wait state */
    FLASH_SetLatency(FLASH_Latency_2);
 
    /* HCLK = SYSCLK */
    RCC_HCLKConfig(RCC_SYSCLK_Div1);
 
    /* PCLK2 = HCLK */
    RCC_PCLK2Config(RCC_HCLK_Div1);
    /* PCLK1 = HCLK/2 */
    RCC_PCLK1Config(RCC_HCLK_Div2);
    /* PLLCLK = 8MHz * 9 = 72 MHz */
    RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);
    /* Enable PLL */
    RCC_PLLCmd(ENABLE);
    /* Wait till PLL is ready */
    while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
    {
    }
    /* Select PLL as system clock source */
    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
    /* Wait till PLL is used as system clock source */
    while(RCC_GetSYSCLKSource() != 0x08)
    {
    }
  }
   
  /* Enable GPIOx and AFIO clocks */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOB, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3,ENABLE);
}
/*******************************************************************************
* Function Name  : GPIO_Configuration
* Description    : Configures the different GPIO ports.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;
 /* Configure USART3 Tx (PB.10) as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;      //////////////////////////////////
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOB, &GPIO_InitStructure);
   
  /* Configure USART3 Rx (PB.11) as input floating */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_Init(GPIOB, &GPIO_InitStructure);  /////////////////////////////////////////
    /* Configure PA2 (PA.02) as 485 control */ ///////////////////////
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
}
/*******************************************************************************
* Function Name  : NVIC_Configuration
* Description    : Configures Vector Table base location.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
void NVIC_Configuration(void)
{
#ifdef  VECT_TAB_RAM 
  /* Set the Vector Table base location at 0x20000000 */
  NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0);
#else  /* VECT_TAB_FLASH  */
  /* Set the Vector Table base location at 0x08000000 */
  NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);  
#endif
}
/*******************************************************************************
* Function Name  : PUTCHAR_PROTOTYPE
* Description    : Retargets the C library printf function to the USART.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
PUTCHAR_PROTOTYPE
{
  /* Write a character to the USART */
  USART_SendData(USART3, (u8) ch);
  /* Loop until the end of transmission */
  while(USART_GetFlagStatus(USART3, USART_FLAG_TXE) == RESET)
  {
  }
  return ch;
}
#ifdef  DEBUG
/*******************************************************************************
* Function Name  : assert_failed
* Description    : Reports the name of the source file and the source line number
*                  where the assert_param error has occurred.
* Input          : - file: pointer to the source file name
*                  - line: assert_param error line source number
* Output         : None
* Return         : None
*******************************************************************************/
void assert_failed(u8* file, u32 line)
{
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* Infinite loop */
  while (1)
  {
  }
}
#endif
/******************* (C) COPYRIGHT 2007 STMicroelectronics *****END OF FILE****/
 

安

电脑超级终端是接收232电平，如果你以485发送，那么需要一个485转232；