For example, it can be downloaded, but the program can not breakpoints, ran into the problem can not be the main function.
You should pay attention to stm32 of Boot0 and Boot1 the pin.
On each of the STM32 chip has two pins and BOOT0 BOOT1,
These pins are in the state where the chip-level reset After reset determine which area the program begins execution,
As follows:
BOOT1 = x BOOT0 = 0 flash boot from the user, which is the normal operating mode.
BOOT1 = 0 BOOT0 = 1 to boot from the system memory, the boot program mode function set by the manufacturer.
BOOT1 = 1 BOOT0 = 1 to boot from the built-in SRAM, this model can be used for debugging.
That is, if you want to debug, to BOOT1 ground, pull BOOT0,
But the situation is that as long as their own tests on BOOT0 pull on the line.