DFU Bootloader

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All STM32 MCUs have a built-in bootloader which will allow reflashing. The Boot0 pin is used to toggle between "normal" boot and this bootloader. Unfortunately this process can not be controlled without manipulating the Boot0 pin, so if we want to control this from our application, we will have to implement our own bootloader.

Overall Architecture

All STM32 MCUs (indeed all ARM processors) follows the Von Neumann architecture. This essentially - in this context - means that the instruction and data memory share the same address space. Since STM32 processors are 32-bit processors and since 32-bit addresses can address 4GB (4,294,967,296 bytes), sharing the address space between instruction and data memory is not a problem.

On STM32s, programs are stored in on-chip flash memory. Different STM32s have different amount of flash memory, but common for all is that it is mapped in the address space starting from 0x08000000.

Start Addr (incl.) End Addr (not incl.) Size (hex) Size (kb)
End --> 0x8078000 0x8080000 0x8000 32 kB
0x8070000 0x8078000 0x8000 32 kB
0x8068000 0x8070000 0x8000 32 kB
0x8060000 0x8068000 0x8000 32 kB
0x8058000 0x8060000 0x8000 32 kB
0x8050000 0x8058000 0x8000 32 kB
0x8048000 0x8050000 0x8000 32 kB
0x8040000 0x8048000 0x8000 32 kB
0x8038000 0x8040000 0x8000 32 kB
0x8030000 0x8038000 0x8000 32 kB
0x8028000 0x8030000 0x8000 32 kB
0x8020000 0x8028000 0x8000 32 kB
0x8018000 0x8020000 0x8000 32 kB
0x8010000 0x8018000 0x8000 32 kB
0x8008000 0x8010000 0x8000 32 kB
Begin --> 0x8000000 0x8008000 0x8000 32 kB

Under normal reset (Boot0 not activated), the MCU will jump to address 0x8000000 and begin execution from there.

Start Addr (incl.) End Addr (not incl.) Size (hex) Size (kb) Usage
End --> 0x8078000 0x8080000 0x8000 32 kB Application (480 kB)
0x8070000 0x8078000 0x8000 32 kB
0x8068000 0x8070000 0x8000 32 kB
0x8060000 0x8068000 0x8000 32 kB
0x8058000 0x8060000 0x8000 32 kB
0x8050000 0x8058000 0x8000 32 kB
0x8048000 0x8050000 0x8000 32 kB
0x8040000 0x8048000 0x8000 32 kB
0x8038000 0x8040000 0x8000 32 kB
0x8030000 0x8038000 0x8000 32 kB
0x8028000 0x8030000 0x8000 32 kB
0x8020000 0x8028000 0x8000 32 kB
0x8018000 0x8020000 0x8000 32 kB
0x8010000 0x8018000 0x8000 32 kB
0x8008000 0x8010000 0x8000 32 kB
Begin --> 0x8000000 0x8008000 0x8000 32 kB Bootloader (32 kB)

Bootloader

Application

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