stm32之printf重定向

</pre><p style="padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:0px; clear:both; height:auto; overflow:hidden">在stm32平臺上實現printf重定向的方式有兩種，重定向至UART，或者通過JTAG的SW模式將printf重定向至SWO引腳輸出。</p><p style="padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:0px; clear:both; height:auto; overflow:hidden">首先介紹第一種，重定向至UART，這種方式我們比較熟悉，ST官方提供的固件庫中也是使用的這種方法。</p><p style="padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:0px; clear:both; height:auto; overflow:hidden">代碼如下：在對UART進行初始化後，通過如下代碼對printf進行重定向</p><p style="padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:0px; clear:both; height:auto; overflow:hidden">1.串口初始化</p><p style="padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:0px; clear:both; height:auto; overflow:hidden"></p><pre code_snippet_id="430608" snippet_file_name="blog_20140719_2_6796295" name="code" class="cpp">  USART_InitTypeDef USART_InitStructure;
  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;
  STM_REDBULL_COMInit(COM1, &USART_InitStructure);

2.printf重定向至串口

int fputc(int ch, FILE *f)
{
  USART_SendData(USART1, (uint8_t) ch);
  /* Loop until the end of transmission */
  while (USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET)
  {}
  return ch;
}

<span style="font-family: Arial, Helvetica, sans-serif;">3.通過printf輸出調試信息</span>

printf("AD value = 0x%04X\r\n", AD_value);

4.連接串口，通過串口調試助手等軟件進行查看

第二種是通過SWO引腳輸出顯示

1.在源碼中添加對ITM端口寄存器的定義

#define ITM_Port8(n)    (*((volatile unsigned char *)(0xE0000000+4*n)))
#define ITM_Port16(n)   (*((volatile unsigned short*)(0xE0000000+4*n)))
#define ITM_Port32(n)   (*((volatile unsigned long *)(0xE0000000+4*n)))

#define DEMCR           (*((volatile unsigned long *)(0xE000EDFC)))
#define TRCENA          0x01000000

2.通過如下代碼將printf的輸出重定向至ITM的Port 0

int fputc(int ch, FILE *f) 
{
  if (DEMCR & TRCENA) {
    while (ITM_Port32(0) == 0);
    ITM_Port8(0) = ch;
  }
  return(ch);
}

3.通過printf輸出調試信息

printf("AD value = 0x%04X\r\n", AD_value);

4.將Jtag設置爲SW模式，並設置ITM的Port 0 獲取信息。

5.在調試狀態下打開 View - Serial Windows - Debug (printf) Viewer 窗口，運行程序即可看到輸出。