STM32 串口数据 Printf函数发送

`#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 */

/**

• @brief Retargets the C library printf function to the USART.
• @param None
• @retval None
  /
  PUTCHAR_PROTOTYPE
  {
  / Place your implementation of fputc here /
  / e.g. write a character to the EVAL_COM1 and Loop until the end of transmission */
  HAL_UART_Transmit(&huart2, (uint8_t *)&ch, 1, 0xFFFF);
  return ch;
  }`