AN1633/0303

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AN1633

APPLICATION NOTE

DEVICE FIRMWARE UPGRADE (DFU) IMPLEMENTATION IN

NON-USB APPLICATIONS

by Microcontroller Division Applications

1 INTRODUCTION

This application note describes how to implement the Device Firmware Upgrade (DFU) capa-

bility using a ST7 USB microcontroller like the ST72F62 or ST72F63B in a general purpose or

‘non-USB’ application. The term ’non-USB’ is used here to contrast with ‘USB application’

which has a different DFU implementation (refer to AN1577). In the implementation described

here, the USB interface is not used in the application. The application board is self powered

and the on-chip USB interface is only used occasionally, as a maintenance utility port to up-

grade the MCU firmware.

The USB cell is only activated when the USB cable is plugged-in. At this time the application

is stopped and the microcontroller is seen as a USB device and enters the DFU process to

erase and program the new firmware in Sector 1 and/or Sector 2. When the user removes the

USB cable, the USB cell is switched-off and the main application is executed !

To illustrate this application note, a firmware example has been developed using a ST72F62

or a ST72F63B USB Low-Speed device. This firmware is based on the ST7 USB Low-Speed

DFU Demo firmware.

It is not necessary to know the USB cell to understand this application note. For more informa-

tion about the USB DFU class, please refer to the Application Note AN1577.

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