I have a system based on STM32F103 microchip. It has a PCB boot0 pin which is used only when flashing new firmware. During the daily usage of the system, the PCB boot0 is not connected to anything. I have always connected to 1.5 Volts input in order to make it to the bootloader mode and flash it with a new firmware, when needed. I have done it for about a year on a weekly basis, without any problems. The 1.5 Volt input was chosen in order to work "safely" and not to give too high voltage (the max value it can handle according to its datasheet is 9 Volts).
But today it got stuck on the boot0 bootloader mode and can't get back to the regular mode (when boots from the internal 0x08000000 flash). I can see using SWD hardware debugger that the PC is in the area of 0x1FFFF7XX, which is related to boot mode ROM. Since I am not the system engineer of that PCB device, I can't tell whether it is connected to specific resistors or not.
Is there any way to get it back to the boot-from-flash regular mode? Or any way to disable the boot0 mode via SWD/JTAG? Or maybe I have damaged the boot0 internal IC?
You should have "Boot0" and "Boot1" pins on your STM32F103 MCU. If you are applying power to the Boot0, what are you doing with your other BOOT pin? The table below shows the modes of boot loading depending on the pin configuration. If you have been leaving your Boot1 floating, it could have corrupted memory locations by disrupting the flash process or have uploaded to the wrong memory causing SRAM vector table issues.
I typically just leave both of my Boot loaders to ground and have not had any issues.
If your device is locked up and not accepting a new program, you can hold down your reset button on the MCU. Then, start to load the program with your computer software, and after it starts to connect, release your reset button. This can sometimes help bypass things that get set wrong and or corrupted memory.
