USB_DEVICE_Open Function

This function opens the USB device layer instance specified by instance index and returns a handle. This handle must be provided to all other client operations to identify the caller and the instance of the USB device layer. An instance of the Device Layer can be opened only once. Trying to open the Device Layer more than once will return a invalid device layer handle.

USB_DEVICE_HANDLE USB_DEVICE_Open(
    const SYS_MODULE_INDEX instanceIndex, 
    const DRV_IO_INTENT intent
);

Preconditions

This function must be called after USB device driver initialization and after the initialization of USB Device Layer.

Parameters

Parameters	Description
instanceIndex	USB device layer instance index
intent	This parameter is ignored. The Device Layer will always open in read/write and exclusive mode.

Returns

If successful, returns a valid device layer handle. Otherwise, it returns USB_DEVICE_HANDLE_INVALID.

Remarks

None.

Example

// This code example shows how the 
// USB Device Layer can be opened.

USB_DEVICE_HANDLE usbDeviceHandle;

// Before opening a handle, USB device must have been initialized 
// by calling USB_DEVICE_Initialize().

usbDeviceHandle = USB_DEVICE_Open( USB_DEVICE_INDEX_0, 
                                DRV_IO_INTENT_READWRITE );

if(USB_DEVICE_HANDLE_INVALID == usbDeviceHandle)
{
    //Failed to open handle.
}

USB Libraries Help > USB Device Libraries > USB Device Layer Library > Library Interface > b) Client Core Functions > USB_DEVICE_Open Function

MPLAB Harmony USB Stack

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