1 UART Introduction

UART is a common peripheral in processors and is usually used for system log information output, low-cost human-computer interaction, communication between devices, and so forth. Particularly common in vehicle communications, the Lin bus often uses UART as a low-cost serial communication protocol. UART does not need both clock synchronization and master-slave settings, only the configuration of the start bit and stop bit is required, since it is an asynchronous communication, and it can send and receive data at any time. TX and RX are sufficient for the external hardware connections when flow control and level conversion are not required. However, in common debugging processes, log information often needs to be output to the computer. Therefore, in hardware design, a USB serial port chip is required to convert the TTL level into a USB serial port protocol and output it to the computer port. Software tools on PC need properly set the serial port parameters applied in the processor driver, including baud rate, start bit, data bit, parity bit, stop bit, and so on, then the log information can be received for debugging.