MCU can't enter or exit to/from bootloader mode only after power on

[martin br]

Hi,

My MCU is STM32G441VBT6 , this MCU is on PCB I designed myself and I use UART3 in bootloader mode.

My boot0 pin is connected through resistor 10k to GND

And the reset pin is connected to push-button (parallel witch capacitor 100n) and GND.

MCU starts after power on.

When I connect boot0 to VCC, MCU can't enter or exit to/from bootloader mode using reset button. Bootloader works only after power on.

MCU restarts when I push reset button. MCU also restarts when I use wachdog.

Can you help me, please, why I can't enter or exit to/from bootloader using reset button.

I tried this situation on other MCU such as stm32F030F4, stm32F103C8T6, stm32L100RCT6 . MCUs successfully enter or exit to/from bootloader mode with reset button.

[AScha.3]

where in G441 manual is boot with reset written? (some cpu booload only on power up)

[Bob S]

Does you firmware modify the FLASH option register (FLASH_OPTR)? According to the ref man, the option register is only loader on power-on reset or when the OBL_LAUNCH bit is set in the FLASH_CR. Whether the bootloader runs depends on the states of the FLASH_OPTR bits nBOOT1 and nBoot0_SW in addition to the BOOT0 pin being pulled high. See AN2606 pattern 6. See also RM0440 (G4xx ref man) section 2.6.1 (Boot Configuration).