UM0463

USB control functions for nondata transfer

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5

USB control functions for nondata transfer

The user application should be aware of a few other USB functions. Same as the data

transfer function, these functions are part of the USB library.

5.1

Library initialization

To use the library certain initializations need to be done. If the USB support is needed in the

application, then the application has to initialize the USB by calling the Init_USB function

and the descriptor table pointer by the descriptor table address. The Init_USB() function

initializes the USB state machine and the configuration state. This function also enables the

Reset interrupt of the USB along with suspend and End of suspend interrupts. After calling

this function, the library will be able to receive the reset from USB.

5.2

Device reset

When the device receives a reset request from the USB, the library initializes the endpoint 0

to acknowledge the SETUP token from host. It then calls the callback function

USER_USB_Reset(). In this function, the user code should reset and initialize the

application on both software and hardware. This function is part of the interrupt routine. The

restriction of an interrupt routine is applied.

5.3

Start of frame

If the start of frame interrupt is enabled, the callback function USER_USB_SOF() is called

every time a start of frame (SOF) token arrives. In this function, the user code can perform

some timing related operations. This function is part of the interrupt routine. The restriction

of an interrupt routine is applied.

Two functions are provided to enable and disable the interrupt of arrival of SOF:

void Enable_SOF(void);

void Disable_SOF(void);