STM32F103C8 bootloader unable to launch after power up...

ming2 · ‎2023-06-22

Hi, Everyone,

I am having a strange problem with my board loaded STM32F103C8T6:

Case 1: With blank MCU, Bootloader via USART1 can only be activated ONCE after power up. (Boot0 pin was soldered to Vcc for testing.) It will never be able to enter BL again after disconnect until power cycled. Error message from programmer:

Case 2: If firmware is downloaded first (via SWD), BL will be able to launch with either power on or reset manually after power on. But some time still fail by manual reset. (about 50%) Here is the screen once it is lauched:

Any idea everyone??? I am in screwed.

STOne-32 · ‎2023-06-23

In that case, it may happen that reset pin is more resetting the device , if you can probe it and check external circuitry . As sampling the boot mode is only done after device reset .

STOne-32 · ‎2023-06-23

In that case, reset pin is suspected no more functional . You may need to probe it if it goes low for enough time to trig a reset .

ming2 · ‎2023-06-23

I did probe the reset pin which was no issue found. I also solder a push button to it so I can control the length of reset as I need. On the board, there is a open drain reset chip which last 140ms after 3.3v established. I parallel a push button to it. The test was going ok but the result was unhappy: BL was not launch as it should.

ming2 · ‎2023-06-26

Tried many boards, I can confirm now that this F103C8 mcu can only launch its BL by power cycling with boot0 high. It will not work by RESET after power up! Is it something to do with POR of the chip or something else? Need help to fix it.

RhSilicon · ‎2023-06-26

@ming2 wrote:
Tried many boards, I can confirm now that this F103C8 mcu can only launch its BL by power cycling with boot0 high. It will not work by RESET after power up! Is it something to do with POR of the chip or something else? Need help to fix it.

Hi, just to comment on something I noticed. In the first message appears the size of 128kB of Flash, the F103C8 model has only 64kB. I already bought BluePill with F103CB (letter B instead of number 8). The F103CB is 128kB of Flash. I believe that there is not much difference in functioning, but it might be interesting to check the specific documents, including Errata if there are any.

https://www.st.com/en/microcontrollers-microprocessors/stm32f103cb.html

https://www.st.com/en/microcontrollers-microprocessors/stm32f103c8.html

ming2 · ‎2023-06-27

You are right! It supposes to be 64k for F103C8. So is it a counterfeit ? Can you tell by the pic:

RhSilicon · ‎2023-06-28

I really can't say if it's original, it's better to ask ST :grinning_face_with_sweat:

STOne-32 · ‎2023-06-28

That marking seems 99% not original and I never seen no proper finish with our laser marking. Or also device original but defective from F103CB part and then re-conditioned and soldered . The only way to know is to return it to ST or thru your distribution channel .

ming2 · ‎2023-06-28

Thanks for your info. I will ask JLC for details.

However, just for compare, I bought few F103C8 from local Digikey (prg shows 64k indeed), and the BL behaves the same: No active on RESET but on power cycle.

ming2 · ‎2023-06-28

Hi, STOne-32,

Just to confirm that I tried a F103RE without any problem on BL. It can be easily activated by reset during live run. That means F103Cx indeed has problem with BL!