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 ARMbased 32-bit MCUs reference manual (RM0090)

●STM32F405xx STM32F407xx datasheet

●STM32F415xx STM32F417xx datasheet

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

October 2011

Doc ID 022318 Rev 1

1/14

www.st.com

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).

1.1Implementing the firmware upgrade application

	The firmware upgrade application contains the source files in Table 1.
Table 1.	Source files
	File	Contents
main.c		Contains the USB initialization data. The USB Host state machine is then
		executed if the user wants to execute the firmware upgrade application or the
		program will execute the user code
stm32f4xx_it.c		Contains the interrupt handlers for the application
command.c		Contains the firmware upgrade commands (DOWNLOAD, UPLOAD and JUMP
		commands)
flash_if.c		Provides a medium layer access to the STM32 embedded Flash driver
usb_bsp.c		Implements the board support package for the USB Host library
usbh_usr.c		Includes the USB Host library user callbacks
system_stm32f4xx.c		Contains the system clock configuration for STM32 F4xx devices

2/14	Doc ID 022318 Rev 1

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
			> 3 seconds	UPLOAD command will be executed immediately after
	Pressed			completed execution of the DOWNLOAD command.
			< 3 seconds	Only the DOWNLOAD command is executed.
Note:	The UPLOAD command condition verification is signaled by the blinking state of the blue
	LED.

Doc ID 022318 Rev 1

3/14

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.

4/14	Doc ID 022318 Rev 1

AN3990	Firmware upgrade overview

1.2LEDs 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.

1.3Commands description

The firmware upgrade application commands are listed in Table 3.

	Table 3.	Supported commands
	Command		Description
	DOWNLOAD		Reads the defined image file “DOWNLOAD_FILENAME” from the thumb
			drive and writes it to the embedded Flash memory.
	UPLOAD		Reads the entire embedded Flash memory and saves the contents to the
			defined file name “UPLOAD_FILENAME” in the thumb drive.
	JUMP		Executes the user code at the defined user application start address
			“APPLICATION_ADDRESS”.
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.

Doc ID 022318 Rev 1

5/14