STM32 HAL库 printf输出重定向

STM32 HAL库串口输出函数为 HAL_UART_Transmit（&huart1，（uint8_t*）&ch,1,0xFFFF）

1. #ifdef __GNUC__
   /* With GCC, 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__ */
   
   
   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;
   }