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USING THE ST7 USB LOW-SPEED LIBRARY V4.2x

4.2.1 Handle_USB_Events function

Most of the work of the USB Library is performed by this function and the private USB Library

functions that it calls. The events to be handled are the assorted USB interrupts that may

occur as a result of USB transaction or changes in the state of the bus. The interrupt service

routine (INT_Usb) copies the event information to a variable (USBCtrFlag) where the

“Handle_USB_Events” function can access it. The event processing occurs when this function

is called from the main loop of the application.

This function is responsible for handling all standard (“Chapter 9”) requests as well as all re-

quests for HID class descriptors (HID, Report or Physical). It is also responsible for STALLing

all unsupported (as indicated via the switches in USB_Opts.h) and invalid USB requests.

Note: Some USB requests will require attention from the application side of the code (non-

descriptor HID requests and all Vendor-specific requests). These requests are addressed in

the Application function “Do_App_Requests”.

Figure 2: Handle_USB_Events architecture

?

Return

YES

NO

void Handle_USB_Events (void)

Correct IT transfer

by H/W

detected

on EP0

[SETUP or IN or OUT]

Process the Correct IT Transfer

Re-enable transmission/Reception

on EndPoint0

on EndPoint0