(3) 移植 fputc 函数
int fputc(int ch, FILE *f)
{
/* Place your implementation of fputc here */
/* e.g. write a character to the USART */
USART_SendData(USART1, (u8) ch);
/* Loop until the end of transmission */
while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET)
{
}