串口一转四的模块，包括了原理图和PCB版图。另外还有主要芯片VK3214的资料和通信协议的介绍-Serial 1 turn four modules, including schematic and PCB layout. There is also the main chip VK3214 information and communication protocols introduced

基于Atmega128微处理器，VK3214串口扩展芯片，RS232方式实现一转四串口扩展-Four serial port expansion to achieve a turn-based Atmega128 microprocessor, VK3214 serial port expansion chip, RS232 mode