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

4.2 SHARED FUNCTIONS

The table below shows all the functions shared between the Library and the Application. Some

functions have been written especially to transfer data over the USB. In order to improve the

flexibility and control over the USB flow some functions have been changed compared to the

Library Version 3. These new functions will allow also to build a report directly into the End-

Point buffer in case the RAM size is critical. The most important functions are described in de-

tail below.

USBbRequest

USB_Var.c

USB_Def.h

Specific request. Refer to USB spec ver 1.1, chap 9.3, page

183. Possible values are :

GET_STATUS, CLEAR_FEATURE_STALL,

SET_FEATURE_STALL, SET_ADDRESS,

GET_DESCRIPTOR, SET_DESCRIPTOR,

GET_CONFIGURATION, SET_CONFIGURATION,

GET_INTERFACE, SET_INTERFACE

USBwValue[2]

USB_Var.c

Word-sized field that varies from request. It is used to pass a pa-

rameter to the device, specific to the request. Refer to USB spec

ver 1.1, chap 9.3, page 183.

USBwIndex

USB_Var.c

Word-sized field that varies from request. Typically used to pass

an index or offset. Refer to USB spec ver 1.1, chap 9.3, page

183.

USBwLength

USB_Var.c

Number of bytes to transfer if there is a data stage. Refer to USB

spec ver 1.1, chap 9.3, page 183

USBDataXferStatus

USB_Var.c

USB_Def.h

Used to send and receive more than 8 bytes for HID requests

(i.e. SetFeature, GetFeature, etc.)

Function

File

Description

Init_USB_HW

USB_Lib.c

Switch ON the USB cell (connect the peripheral to

the bus) and initialize Library variables.

Disable_USB_HW

USB_Lib.c

Switch OFF the USB cell (disconnect the peripheral

from the bus) and reset Library variables.

Handle_USB_Events

USB_Lib.c

Manage USB flow (interrupts) on EndPoint0 and

process standard requests only. Manage also all re-

quests for HID class descriptors (HID, Report or

Physical). It’s also responsible for STALLing all un-

supported and invalid USB requests.

Enable_STATUS_Stage

USB_Lib.c

Allow ST7 to ACK or STALL incoming status stage

after completion of a non standard request. This

function is called by Application once the

APP_REQUESTS processing is done in the

Handle_APP_Requests function.

Variable

Declaration/

Aliases

Description