What is the CDC class (Communication Device Class)

Full Text address: http://justmei.blog.163.com/blog/static/1160998532010321112522467/

What is the CDC class (Communication Device Class)

The CDC class for USB is the abbreviation for the USB Communication device class (Communication device Class). The CDC class is a USB subclass defined by the USB organization that is dedicated to a variety of communication devices (telecommunications and medium-speed network communication devices). The CDC class is divided into the following different models, depending on the communication device that the CDC class is based on: USB Traditional Pure Telephone service (POTS) model, USB ISDN model and USB network model. Among them, the USB traditional pure telephone service model can be divided into Direct Line control model, abstract control model and USB phone model (USB telephone models). As shown in 1. The virtual serial port discussed in this paper belongs to the abstract control model under the USB traditional pure telephone service model.

Typically a CDC class consists of two socket classes that form the Communication interface Class (communication Interface Class) and the data Interface class. The author mainly through the communication interface class to the device management and control, and through the data interface class transmission data. These two interface subclasses occupy different numbers and types of end points (endpoints), as shown in 2. For the different CDC class models described earlier, the end point requirements for the corresponding interfaces are also different. As required for the abstract control model to be discussed, the communication interface class requires a control endpoint (controlled Endpoint) and an optional interrupt (Interrupt) endpoint, The data interface subclass requires a periodic (isochronous)-type end point in the direction of input (in) and a periodic terminal point with a direction of output (out). The control terminal point is mainly used for the enumeration of USB devices and the communication of the baud rate and data type (data bits, stop bit and start bit) of the virtual serial port. The asynchronous end point of the output direction is used by the host to send data to the slave device (Slave), which is equivalent to the TXD line in the traditional physical string (if viewed from a single-chip computer), and the asynchronous end point of the input direction is used to send data from the device to the host, equivalent to the RXD line in the traditional physical string.

(turn) What is the CDC class (Communication Device Class)