The serial programming steps

Serial programming step (non-breaking) as follows:

　　Enable GPIO clock

　　Enable serial clock

　　TXD is configured + pull alternate function (standing STM32 chip angle)

　　Configured to multiplex RXD + pull function (standing STM32 chip angle)

　　Setting data frame

　　　　OVER8 bit configuration (selection oversampling)

               Packet settings, including start bits, stop bits, data bits

　　Parity disabled

　　Set the baud rate

　　Enable transmitter

　　Receiver Enable

　　Enables the serial port