CH340 is a USBbus convert chip and it can realize USB convert to serial interface, USB convert to IrDA infrared or USB convert to printer interface.

In serial interface mode, CH340 supplies common MODEM liaison signal, used to enlarge asynchronous serial interface of computer or upgrade the common serial device to USBbus directly.

More detail about USB convert to printer interface please referring to the second manual CH340DS2. In infrared mode, add infrared transceiver to CH340 can compose USB infrared adapter, realize SIR nfrared communication.