Serial communication learning

The processor communicates with external devices

1、 Parallel communication
All bits of data are transmitted at the same time , It is fast but takes up pin resources

2、 serial communication
Data transmission in bit order , Relatively slow

（1） Synchronous communication ： With clock synchronization signal
SPI、IIC signal communication

（2） asynchronous communication ： Without clock signal
UART（ full duplex ）

3、STM32F407ZGT6 Of UART Pin

Serial number	RXD	TXD
1	PA10(PB7)	PA9(PB6)

4、 Serial port related registers
（1）USART_SR Status register

（2）USART_DR Data register

（3）USART_BRR Baud rate register