stm32 输入输出重定向

布满荆棘的人生 2021-11-10 06:18 308阅读 0赞

## STM32重定向printf()和scanf()到UART  ##

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[  大熊猫][Link 1] 发布于 2018/01/22 21:08

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[STM32 printf scanf][]

[撸了今年阿里、头条和美团的面试，我有一个重要发现.......>>> ][.......]![aHR0cHM6Ly93d3cub3NjaGluYS5uZXQvaW1nL2hvdDMucG5n][]

开发环境：

Ubuntu16.04 + SW4STM32 + STM32CubeMX + STM32F103C8T6

说明：scanf()函数有个bug，那就是当我们想要获取一个int时，如果输入了**非**数字，就会导致scanf()永远获取不到用户的输入，除非重启mcu。

STM32CubeMX配置：

![aHR0cHM6Ly9zdGF0aWMub3NjaGluYS5uZXQvdXBsb2Fkcy9zcGFjZS8yMDE4LzAxMjIvMjAzNzUzX3lLeUJfMTA0MTA4Mi5wbmc][]

main.c中添加：

/* With GCC, small printf (option LD Linker->Libraries->Small printf
       set to 'Yes') calls __io_putchar() */
    #define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
    #define GETCHAR_PROTOTYPE int __io_getchar(FILE *f)
    #else
    #define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
    #define GETCHAR_PROTOTYPE int fgetc(FILE *f)
    #endif /* __GNUC__ */
    
    
    PUTCHAR_PROTOTYPE
    {
      /* Place your implementation of fputc here */
      /* e.g. write a character to the USART2 and Loop until the end of transmission */
      HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xFFFF);
    
      return ch;
    }
    
    GETCHAR_PROTOTYPE
    {
      uint8_t ch = 0;
      HAL_UART_Receive(&huart1,(uint8_t *)&ch, 1, 0xFFFF);
    
      if (ch == '\r')
      {
          __io_putchar('\r');
          ch = '\n';
      }
    
      return __io_putchar(ch);
    //  return ch;
    }

复制SW4STM32安装目录中的syscalls.c到自己的project，并按如下修改"\_\_read()"函数。

for (DataIdx = 0; DataIdx < len; DataIdx++)
     	{
    -		*ptr++ = __io_getchar();
    +		*ptr = __io_getchar();
    +		if (*ptr++ == '\n') break;
     	}
      
    -return len;
    +    return ++DataIdx;
    }

[Link 1]: https://my.oschina.net/igiantpanda
[0]: https://my.oschina.net/igiantpanda/blog/1611419#comments
[STM32 printf scanf]: https://my.oschina.net/igiantpanda?q=STM32%20printf%20scanf
[.......]: https://gio.ren/w/GPnE1LRY
[aHR0cHM6Ly93d3cub3NjaGluYS5uZXQvaW1nL2hvdDMucG5n]: /images/20211109/654937ee568d4fcfbc210ef611547574.png
[aHR0cHM6Ly9zdGF0aWMub3NjaGluYS5uZXQvdXBsb2Fkcy9zcGFjZS8yMDE4LzAxMjIvMjAzNzUzX3lLeUJfMTA0MTA4Mi5wbmc]: /images/20211109/59b7cf761e5a4568b0dd3aaf20df6790.png