DFU Interface Descriptor
| Offset | Field | Size | Value | Descripton |
|---|---|---|---|---|
| 0 | bLength | 1 | 09h | Size of this descriptor,in bytes. |
| 1 | bDescriptorType | 1 | 04h | INTERFACE descriptor type. |
| 2 | bInterfaceNumber | 1 | Number | Number of this interface. |
| 3 | bAlternateSetting | 1 | 00h | Alternate setting. Must be zero. |
| 4 | bNumEndpoints | 1 | 00h | Only the control pipe is used. |
| 5 | bInterfaceClass | 1 | FEh | Application Specific Class Code. |
| 6 | bInterfaceSubClass | 1 | 01h | Device Firmware Upgrade Code. |
| 7 | bInterfaceProtocol | 1 | 01h | Runtime protocol. |
| 8 | iInterface | 1 | index | Index of string descriptor for this interface. |
