Enter System Bootloader by Software on STM32U375/85 + Flashing via UART

[Vrushabh_1157]

Hello,

We are using STM32U375xx/85xx MCUs and want to implement firmware update over UART using another MCU (ESP32-S3) in out application.
The ESP32 will send the .bin firmware to the STM32 without using any ST utility (e.g., CubeProgrammer).

From the STM32 AN2606 bootloader document, I understand that normally BOOT0/BOOT1 pins must be set to enter System Memory.

Question 1 — Entering Bootloader via Software

We want to enter the system bootloader purely by software, without toggling hardware BOOT pins.
How can this be done on the STM32U3 series?

Question 2 — Flashing Over UART from ESP32

Could someone provide the correct sequence for flashing a .bin into STM32U375/85 using the UART bootloader protocol?
(ESP32 will send the commands directly — no STM32CubeProgrammer involved.)

Steps I am looking for:

• entering bootloader

• UART initialization

• bootloader command sequence (GET, GETID, ERASE, WRITE, GO)

• any STM32U3-specific notes

Thanks in advance for any guidance.

[mƎALLEm]

Hello,

You need to refer to the AN3155 USART protocol used in the STM32 bootloader.

[Vrushabh_1157]

Hello @mƎALLEm,

Thank you for your response.

I read the AN2606 document, which explains the USART configuration and the bootloader settings.

Normally, to flash a .hex or .bin file, we need to boot from the System Memory using the BOOT pins. However, I want to boot(system boot) my ST controller using from my application code, without using the hardware BOOT pins. In other words, I want to trigger the bootloader by software instead of configuring the BOOT pins physically.

Note - I am not using STM programmer utility or any STM utility 

Thanks,

Vrushabh Kale

[mƎALLEm · Accepted solution]

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@Vrushabh_1157 wrote:

Hello @mƎALLEm,

However, I want to enter the system bootloader from my application code, without using the hardware BOOT pins.

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Please refer to this knowledge base: How to jump to system bootloader from application code on STM32 microcontrollers