stm32中的串口管腳

USART1_CK ------ PA8
USART1_TX ------ PA9
USART1_RX ----- PA10
USART1_CTS ----- PA11
USART1_RTS ----- PA12

USART2_CTS ----- PA0
USART2_RTS----- PA1
USART2_TX ----- PA2
USART2_RX ----- PA3
USART2_CK ----- PA4

USART3_TX ----- PB10
USART3_RX ----- PB11
USART3_CK ----- PB12
USART3_CTS ----- PB13
USART3_RTS ----- PB14

USART4_TX ----- PC10
USART4_RX ----- PC11

USART5_TX ----- PC12
USART5_RX ----- PD2