Datasheet

Figure 5. Correspondence between source code and USB protocol stack architecture
The basic workflow of the device stack depends on callback functions and function calls. The callback functions notify all state
changes and data requests of the device stack to application.
There are two types of callback functions in the device stack:
• Device callback function - It notifies the state of device stack to the application.
• Endpoint callback function - It notifies the data transfer result of the corresponding endpoint to application. The control
endpoint callback function handles all USB standard requests and class requests. The Figure 6 briefly describes the
processing of the callback function.
NXP Semiconductors
Software workflow chart
USB to Multi VCOM on K32L2 Series MCU, Rev. 0, November 2019
Application Note 9 / 25