void USART3_Handler(void)
{
  Serial3.IrqHandler();
}
void USART1_Handler(void)
{
  Serial2.IrqHandler();
}
//Serial.begin() mapped to USART3(PC10,PC11)
void USART3_IRQHandler(void) 
{
  Serial.IrqHandler();
}
// IT handlers
void USART0_Handler(void)
{
  Serial1.IrqHandler();
}
// IT handlers
void USART1_IRQHandler(void) 
{
  Serial.IrqHandler();//USART1 must be Serial,for usart flash programming.
}