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Bootloader-Host Communication

Introduction

• According to the Application Note (AN2606), the bootloader of the STM32F40xxx MCU can communicate with the host over various peripheral interfaces such as USART, CAN, etc.

• USART2 peripheral is used for the Virtual COM Port support.

Bootloader-Host Communication over USART Peripheral Interface

Overview

Host Application

• The host application runs on a host machine and provides the user with an interactive menu of the available bootloader commands.

Using the Virtual COM Port

• For STM32F407-Discovery board, the USB-to-UART converter will be necessary. (See Virtual COM Port (VCP) Support)

• For STM32F446-Nucleo board, the USB-to-UART converter will not be necessary since the USART2 peripheral can communicate with the host directly over the USB interface.

Using the Debug Port (Optional)

• Select one USART peripheral (i.e., USART1 or USART3)

  • Note that the USART2 peripheral is not available for the system memory boot mode since it is used for the Virtual COM Port support.

• Connect the board to the host PC using the USB-to-UART adapter as shown in the image below.

• Download the STM32 Flash Loader Demonstrator (UM0462) (replaced by STM32CubeProgrammer)

• To boot from the system memory, configure the boot pins as follows:

  • BOOT0 - HIGH (Vcc = 3V)

  • BOOT1 - LOW (GND)

  Although it appears that the BOOT1/PB2 pin is pulled to GND by default, it was not the case when I tested it with the STM32F407-Discovery board. If you want to boot from the system memory, make sure to connect the BOOT1/PB2 pin to GND, in addition to connecting the BOOT0 pin to Vcc (3V).

• Run the STM32 Flash Loader Demonstrator, select the correct port for the USB-to-UART communication and press next. You should be brought to the next page if everything has been successful.