重定向printf

#include "stdio.h"

#ifdef __GNUC__
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif 
PUTCHAR_PROTOTYPE
{
HAL_UART_Transmit(&huart2 , (uint8_t *)&ch, 1, 0xFFFF);
return ch;
}