针对VK33XX系列芯片的IIC接口通信，可实现串口的扩展-For VK33XX Series IIC interface chip communication, serial port expansion can be achieved

VK32、VK33系列的串口驱动程序例程，包括SPI转串口，IIC转串口和USART转串口三种方式。-VK32, VK33 series of serial driver routines, including SPI serial transfer, IIC-serial and USART serial transfer in three ways.

wk21xx串口扩展收发控制标准，一个串口扩展为四个-Wk21xx u4E32 u53E3 u6269 u5C55 u6536 u53D1 u63A7 u5236