Saturday, September 14, 2013

STM32 Firmware Loader

For some of my hobby projects I'm using STM32 MCU. To make my life easier when loading different firmwares I created this simple STM32 Firmware Loader.

Using a software USB boot-loader has some disadvantages:

  • It has to occupy some part of the user Flash, which leads to less available Flash memory (usually a whole page)

  • it is difficult (or impossible) to protect it from accidental erase or data corruption.

  • the user firmware has to be build with the boot-loader in mind

  • it has to have own USB PID/VID. Having a VID is a little bit expensive, especially for small hobby projects.

The solution I have is to use the STM32 internal loader. This allows me to use the whole Flash memory for my user code. On top of that I have some more flexibility with this solution - I have a control over the hardware reset pin from the software.

However, all it comes at a price - an external components are needed. The schematic is very simple. A popular FTDI FT232 USB-to-UART converter is used.

Two GPIO from FT232 are used to control STM32_RESET and STM32_BMODE pins, and two pins for UART communication.


Operation is simple - when a firmware has to be loaded, the boot mode pin is set to enable the internal boot-loader and a hardware reset is issued. The STM32 goes to boot-loader mode. Via UART the new firmware is loaded, the boot pin is set to a state to enable user code execution and the STM32 is reset again. At this point the new firmware gets executed.

The source code can be found on The GUI is based on Qt.

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