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The library package and its configuration

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7.3

Application interface to the library

The application code has to provide some values to the library to execute the state machine.

The library uses callback functions to perform the operation and all callback functions are

implemented by direct function calls which are defined in user_usb.h. These callback

functions are listed in Table 9.

Four variables are there for the application to pass some configuration values to the library:

●

USB_Num_Configuration: number of configuration

●

USB_Num_Interface: number of interface

●

USB_Interrupt_Mask: the value for the USB interrupt mask register

●

DescTabPtr: pointer to actual descriptor table

These variables must be set in (or prior to) the "USER_USB_Reset" function.

Table 9.

Call back functions

Function name

Description

USER_USB_Reset()

Called when a USB Reset is received by the device.

USER_USB_Setup()

All user-interpreted requests are parsed in this function.

USER_USB_CopydataIN()

Used to copy data to the endpoint DMA buffer EP0_IN for

each data packet of data IN stage.

USER_USB_CopydataOUT()

Used to copy data from the endpoint DMA buffer

EP0_OUT for each data packet of data OUT stage.

USER_USB_Status_In()

Called when a status IN stage is executed for all the

requests except Set Address.

USER_USB_Status_Out()

Called when a status OUT stage is executed for all the

requests.

USER_USB_Set_Configuration()

The user code has to configure the device as specified.

USER_USB_Set_Interface()

The user code has to set the alternative setting of an

interface as specified.

USER_USB_Get_Interface()

The user code has to return the alternative setting of an

interface as specified.

USER_USB_Clear_Feature_EP()

The user code is informed that the specified endpoint

STALL condition is cleared.

USER_USB_Set_Feature_EP()

The user code is informed that the specified endpoint is set

as STALL.

USER_USB_SOF()

Called every time a start of frame (SOF) token arrives on

USB given SOF interrupt is enabled.

USER_USB_Suspend()

Called when suspend request is received by the device

from the USB.

USER_USB_ESuspend()

Called when the device is in suspended state and activity

on USB bus is detected