i want to use 3 USART on f103 board (f103-periph), i am adding USART 3 in hwdef file and remove comment on USART 2 ,then i do build and upload the code , when i set parameter port for serial 1 2 3 to use them all , the board give status MAINTENANCE ,however when using only two or one serial ,the board give OPERATIONAL. why this is happening?