When we use scanner, usually we encounter these terms: RS232 physical serial port, USB interface, USB virtual serial port and so on.
So what is the USB virtual serial port? It is estimated that everyone is not very clear, then let us briefly introduce what is a USB virtual serial port.
The USB virtual serial port belongs to the USB communication device class. The physical layer is provided with a physical serial port by means of a virtual serial port through the USB bus at the physical layer. Inside the system, the USB controller provides a bulk transfer IN endpoint and a bulk transfer OUT endpoint for data reception and transmission, simulating the RX and TX lines of the serial port. In addition, the USB controller also provides an interrupt IN endpoint, which sends the status of the current serial port to control the serial port transmission. The data of the serial device is collected by the serial port of the system, and the USB package is packaged in the chip, uploaded to the host through the USB bus, and then processed by the corresponding serial port application. For the user, what is seen is the data acquisition and transmission based on the serial port, but actually realizes the data transmission based on the USB protocol packet.