CH340是一个USB总线的转接芯片，实现USB转串口、USB转IrDA红外或者USB转打印口。

在串口方式下，CH340提供常用的MODEM联络信号，用于为计算机扩展异步串口，或者将普通的串口设备直接升级到USB总线。有关USB转打印口的说明请参考手册（二）CH340DS2。 -CH340 is a USB bus adapter chip, USB to serial, USB to IrDA Infrared, or USB to LPT. MODEM liaison signal in serial mode, CH340, for computer expansion asynchronous serial, or upgrade the ordinary serial devices directly to the USB bus. USB-to-LPT Reference Manual (b) CH340DS2.