07 printf redirection

Modify on the basis of the last experiment , Open it directly keil engineering , Configure the software first .

• open “USART.c” file , add to “#include<stdio.h>” The header file .
  
• Add the following program at the end of this file .

/* USER CODE BEGIN 1 */
int fputc(int ch, FILE *stream)
{
         
    HAL_UART_Transmit(&huart1, (uint8_t *)&ch,1, 0xFFFF);
    return ch;
}
/* USER CODE END 1 */

• Return to the main function after the preparation , Add again “#include<stdio.h>” The header file .
  
• stay while Complete the code in the program .

  while (1)
  {
    /* USER CODE END WHILE */
    /* USER CODE BEGIN 3 */
	  printf("Hello World! \r\n");
	  HAL_Delay(1000);
  }
  /* USER CODE END 3 */

Final output .

notes ： In many places \n You can change lines , But the actual measurement is not good , But through \r\n To achieve .
————————————————————————————————————
The second method ：
stay USART.c Add the following program to the file .

/* USER CODE BEGIN 1 */
__align(8) char USART2_TxBuff[256];  

void u2_printf(char* fmt,...) 
{
      
	unsigned int length=0;
	
	va_list ap;
	va_start(ap,fmt);
	vsprintf(USART2_TxBuff,fmt,ap);
	va_end(ap);
	
	length=strlen((const char*)USART2_TxBuff);
	HAL_UART_Transmit(&huart2, (uint8_t *)USART2_TxBuff, length, 0xffff);
	
	while(__HAL_UART_GET_FLAG(&huart2,UART_FLAG_TC)!=SET);
}

/* USER CODE END 1 */

At the same time USART.c Add the corresponding header file .

/* USER CODE BEGIN 0 */
#include "stdio.h"      
#include "stdarg.h"		
#include "string.h"
/* USER CODE END 0 */

stay usart.h Declare the header file .

/* USER CODE BEGIN Prototypes */
void u2_printf(char* fmt,...) ;
/* USER CODE END Prototypes */

Next, you can test in the main function .

/* USER CODE BEGIN 3 */
    u2_printf("Hello XP\r\n");
	HAL_Delay(1000);
/* USER CODE END 3 */