Datasheet

Figure 1. USB descriptor structure block diagram
In Figure 1, the interface association descriptor associates a CDC interface with a data interface to describe a VCOM function.
For details on the USB descriptor, refer to Chapter 9.6, Standard USB Descriptor Definitions, USB Specification 2.0 and SDK
code.
If the interrupt endpoint of the CDC interface is removed, the serial port status cannot be sent and received. For
example, the RTS and DTR signals in RS232 cannot be transmitted. If the serial port debugging terminal on the
PC is already turned on, the serial port data can still be sent and received.
NOTE
3 Endpoint usage
As described in Chapter 2, each CDC class requires 1 bidirectional endpoint, and 15 CDC classes require 15 endpoints. The
EP0 is used as a control endpoint. The usage of the endpoints of USB devices in this application note is shown in Table 1.
Table 1. Endpoint usage
Endpoint Direction Endpoint type Packet size (byte) Use or not
EP0 OUT Control 64 YES
EP0 IN Control 64 YES
EP1 OUT CDC1 Bulk 64 YES
EP1 IN CDC1 Bulk 64 YES
EP2 OUT CDC2 Bulk 64 YES
EP2 IN CDC2 Bulk 64 YES
EP3 OUT CDC3 Bulk 64 YES
Table continues on the next page...
NXP Semiconductors
Endpoint usage
USB to Multi VCOM on K32L2 Series MCU, Rev. 0, November 2019
Application Note 2 / 25