4

7618C–AVR–07/08

device that supports DFU is not capable of changing its mode of operation on its own. External

(human or host operating system) intervention is required.

4.2

DFU Specific Requests

In addition to the USB standard requests, 7 DFU class-specific requests are used to accomplish

the upgrade operations:

Table 4-1.

DFU Class-specific Requests

4.3

DFU Descriptors Set

The device exports the DFU descriptor set, which contains:

• A DFU device descriptor

• A single configuration descriptor

• A single interface descriptor (including descriptors for alternate settings, if present)

4.3.1

DFU Device Descriptor

This descriptor is only present in the DFU mode descriptor set. The DFU class code is reported

in the bDeviceClass field of this descriptor.

Table 4-2.

DFU Mode Device Descriptor

bmRequestType

bRequest

wValue

wIndex

wLength

Data

0010 0001b

DFU_DETACH (0)

wTimeout

Interface (4)

Zero

none

0010 0001b

DFU_DNLOAD (1)

wBlock

Interface (4)

Length

Firmware

1010 0001b

DFU_UPLOAD (2)

wBlock

Interface (4)

Length

Firmware

1010 0001b

DFU_GETSTATUS (3)

Zero

Interface (4)

6

Status

0010 0001b

DFU_CLRSTATUS (4)

Zero

Interface (4)

Zero

none

1010 0001b

DFU_GETSTATE (5)

Zero

Interface (4)

1

State

0010 0001b

DFU_ABORT (6)

Zero

Interface (4)

Zero

none

Offset

Field

Size

Value

Description

0

bLength

1

12h

Size of this descriptor, in bytes

1

bDescriptorType

1

01h

DFU functional descriptor type

2

bcdUSB

2

0100h

USB specification release number in binary coded decimal

4

bDeviceClass

1

FEh

Application Specific Class Code

5

bDeviceSubClass

1

01h

Device Firmware Upgrade Code

6

bDeviceProtocol

1

00h

The device does not use a class specific protocol on this interface

7

bMaxPacketSize0

1

32

Maximum packet size for endpoint zero (limited to 32 due to Host side

driver)

8

idVendor

2

03EBh

Vendor ID

10

idProduct

2

2FFBh

Product ID

12

bcdDevice

2

0x0000

Device release number in binary coded decimal

14

iManufacturer

1

0

Index of string descriptor