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I2C Bootloader Slave address

abhijith_raj
Associate III

‎2025-06-20 2:10 AM - last edited on ‎2025-06-20 2:34 AM by

Hi,
I’m working on the STM32G491 series. In my current project, the STM32 is configured as an I2C slave and communicates with another processor over I2C.

When entering bootloader mode for flashing, the STM32 responds with the slave address 0x5F, which is also confirmed in the AN2606 application note.

The issue is that the connected processor already has another I2C slave device using the same 0x5F address, and that device’s address cannot be changed.

Is there any way to change the STM32’s I2C slave address in bootloader mode to avoid this conflict?

abhijith_raj_0-1750410440146.png

 

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Andrew Neil
Super User

‎2025-06-20 2:29 AM

No. The bootloader is fixed in ROM.

So you'll either have to use a different I2C peripheral, or some sort of I2C bus switch/multiplexer.

Or could you use a different interface; eg, UART ... ?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.
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