why does my MCU outputs some random signals for 3s before starting the program?

[mohamed chawki chamsi]

Posted on July 13, 2018 at 10:13

Hi, i'm using STM32F407VG discovery board for a project.

I have this problem, when i power up the board it outputs some random signals for 3 to 4 seconds before it starts executing my code.

I did the ST-link update and nothing changed.

Thank you.

#stm32f4-discovery #st-link

[Tesla DeLorean]

Posted on July 13, 2018 at 11:02

Couple of possibilities, either something you've programmed onto the part is doing that, or the ST-LINK is probing the part. You can disconnect the ST-LINK from the SWDIO/SWCLK pins by removing a pair of jumpers.

If that still causes issues you need to look at what you're doing. Perhaps instrument your code so you can see via a GPIO where it is, or use a debugger where you've unchecked 'run to main()' and you step or otherwise walk the code between Reset_Handler and the point where you see 'normal' behaviour.

[mohamed chawki chamsi]

Posted on July 13, 2018 at 14:11

I'll do that thank you