UM0290 datasheet(33/76 Pages) STMICROELECTRONICS

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UM0290

Device firmware upgrade

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4.4

Reconfiguration phase

Once the operator has identified the device and supplied the filename, the host and the

device must negotiate to perform the upgrade.

●

The host issues a DFU_DETACH request to Control Endpoint EP0.

●

The host issues a USB reset to the device. This USB Reset is not possible on some PC

Host OS versions. To bypass this issue, the USB reset is performed by the MCU

depending on the corresponding implementation.

●

The device enumerates with the DFU Mode descriptor set, as described above.

Note:

In some device applications, such as motor control or security systems, it could be the case

that USB is not used in the application run-time mode, and USB might only be used for

memory upgrade. These devices are called non-USB applications in the scope of this

document and the above sequences are not applicable.

Non-USB applications have to carry out the right procedure to enter DFU mode. This can be

done simply by plugging the USB cable or by jumping to the DFU firmware code while

performing an USB reset so that the device enumerates with the DFU descriptor set.

4.5

Transfer phase

The transfer phase begins after the device has processed the USB reset and exported the

DFU Mode descriptor set. Both downloads and uploads of firmware can take place during

this phase. This transfer phase consists of a succession of DFU requests according to the

state diagram described in the following sections.

4.5.1

Requests

A number of DFU class-specific requests are needed to accomplish the upgrade/upload

operations. Table 9 summarizes these requests.

For additional information about these requests, please refer to the DFU Class specification.

Table 9.

Summary of DFU upgrade/upload requests

bmRequest

bRequest

wValue

wIndex

wLength

Data

00100001b

DFU_DNLOAD (1)

wBlockNum

Interface

Length

Firmware

10100001b

DFU_UPLOAD (2)

wBlockNum

Interface

Length

Firmware

10100001b

DFU_GETSTATUS(3)

Zero

Interface

Status

00100001b

DFU_CLRSTATUS (4)

Zero

Interface

Zero

None

10100001b

DFU_GETSTATE (5)

Zero

Interface

State

00100001b

DFU_ABORT (6)

Zero

Interface

Zero

None

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