ST AN3990 APPLICATION NOTE

AN3990

Application note

Upgrading STM32F4DISCOVERY board firmware using a USB key

Introduction

An important requirement for most Flash memory-based systems is the ability to update the firmware installed in the end product. This document provides general guidelines for creating a firmware upgrade application based on the STM32F4DISCOVERY board.

The STM32F4 series microcontroller can run user-specific applications to upgrade the firmware of the microcontroller-embedded Flash memory. This feature allows the use of any type of communication protocol for the reprogramming process (for example, CAN, USART and USB). USB Host mass storage is the example used in this application note.

The firmware upgrade using a USB Host is very advantageous because it is a standalone executed code in which the user does not need to use a host computer to perform the firmware upgrade. The user only needs a Flash disk to upgrade the target STM32 device.

Document contents

● Section 1: Firmware upgrade overview contains an overview of the firmware upgrade

process and demonstrates how to run the firmware upgrade.

● Section 2: How to use the firmware upgrade application describes the user program

and system requirements for the software and hardware.

Reference documents

● STM32F4DISCOVERY STM32F4 high-performance discovery board (UM1472)

● STM32F405xx, STM32F407xx, STM32F415xx and STM32F417xx advanced ARM-

based 32-bit MCUs reference manual (RM0090)

● STM32F405xx STM32F407xx datasheet

● STM32F415xx STM32F417xx datasheet

The above documents are available at www.st.com/stm32f4-discovery.

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Firmware upgrade overview AN3990

1 Firmware upgrade overview

To program the firmware upgrade application to the Flash memory, use the STM32F4xx's embedded Bootloader or any in-system programming tool to easily reprogram this application.

The firmware upgrade application uses the USB Host to:

● Download a binary file (.bin) from a Flash disk (thumb drive) to the STM32F4xx's

internal flash memory.

● Upload all the STM32F4xx's internal Flash memory content into a binary file.

● Execute the user program.

Note: This application note is based on the STM32 USB On-The-Go (OTG) Host and device

library. For more details about the USB Host stack and a mass storage demonstration, please refer to user manual (UM1021).

1.1 Implementing the firmware upgrade application

The firmware upgrade application contains the source files in Tab l e 1 .

Table 1. Source files

File Contents

Contains the USB initialization data. The USB Host state machine is then

main.c

executed if the user wants to execute the firmware upgrade application or the program will execute the user code

stm32f4xx_it.c

command.c

flash_if.c

usb_bsp.c

usbh_usr.c

system_stm32f4xx.c Contains the system clock configuration for STM32 F4xx devices

Contains the interrupt handlers for the application

Contains the firmware upgrade commands (DOWNLOAD, UPLOAD and JUMP commands)

Provides a medium layer access to the STM32 embedded Flash driver

Implements the board support package for the USB Host library

Includes the USB Host library user callbacks

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AN3990 Firmware upgrade overview

After the board reset and depending on the user button state:

1. User button pressed: The firmware upgrade application is executed.

2. User button not pressed: A test on the user application start address will be performed and one of the below processes is executed.

– User vector table available: User application is executed.

– User vector table not available: firmware upgrade application is executed.

During the firmware upgrade application execution, there is a continuous check on the user button pressed state time. Depending on the state time of the user button, one of the following processes is executed.

Table 2. User button state time control

User button state Time Process executed

Pressed

> 3 seconds

< 3 seconds Only the DOWNLOAD command is executed.

UPLOAD command will be executed immediately after completed execution of the DOWNLOAD command.

Note: The UPLOAD command condition verification is signaled by the blinking state of the blue

LED.

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Firmware upgrade overview AN3990

Figure 1 illustrates the Firmware upgrade application flowchart.

Figure 1. Upgrade application flowchart

Note: To execute the UPLOAD command the user button should be kept pressed 3s just after a

board reset, at firmware startup.

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AN3990 Firmware upgrade overview

1.2 LEDs status

The following section describes the LEDs behaviors during the firmware upgrade application execution:

● Red LED blinks in infinite loop

– Error (USB key disconnected, binary file not available or FATFS file system error).

● Red LED blinks in infinite loop and Blue LED ON

– Error (No available Flash memory size to load the binary file).

● Red LED blinks in infinite loop, Blue LED ON and Orange LED ON

– Flash erase error.

● Blue LED ON

– DOWNLOAD ongoing.

● Blue LED ON and Orange LED ON

– DOWNLOAD done; UPLOAD ongoing.

● Blue LED blinks

– UPLOAD condition verified and the user should release the user button.

● Orange LED ON

– DOWNLOAD done.

● Orange LED ON, Blue LED ON and Red LED blinks in infinite loop

– USB key read out protection ON.

● Green LED ON and Orange LED OFF

– DOWNLOAD done with success; and the MCU waiting until you press the user

button to execute the JUMP command.

● Green LED ON and Orange LED ON

– DOWNLOAD and UPLOAD done with success; and the MCU waiting until you

press the user button before execute the JUMP command.

1.3 Commands description

The firmware upgrade application commands are listed in Tab le 3 .

Table 3. Supported commands

Command Description

DOWNLOAD

UPLOAD

JUMP

Note: The maximum length for the file names (DOWNLOAD_FILENAME, UPLOAD_FILENAME)

should be 11 characters as the LFN feature on the FAT file system is a patent of Microsoft® Corporation and when enabling it on commercial products, a license from Microsoft may be required depending on the final destination.

Reads the defined image file “DOWNLOAD_FILENAME” from the thumb drive and writes it to the embedded Flash memory.

Reads the entire embedded Flash memory and saves the contents to the defined file name “UPLOAD_FILENAME” in the thumb drive.

Executes the user code at the defined user application start address “APPLICATION_ADDRESS”.

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