STM32F429I-DISC1 Auto Reset, Debugger Disconnect

[BlueB_Ashutosh]

Hi everyone,

I am facing an issue with my STM32F429I-DISC1 board.

The board automatically resets after around 20–30 seconds and continuous debugging is not possible because debugger disconnects. STM32CubeProgrammer also cannot maintain stable connection for long time.

I tried flashing different simple codes (including LED blink), but same behavior is observed.

I also tried powering the board using external 5V and GND. In that condition, MCU seems to work as expected, but COM LED (LED1 red) continuously blinks and LED2 stays ON.

Can anyone suggest whether this indicates power section issue, ST-Link issue, or MCU damage?

Thanks.

[Andrew Neil]

welcome to the forum

Please see How to write your question to maximize your chances to find a solution for best results.

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@BlueB_Ashutosh wrote:

The board automatically resets after around 20–30 seconds and continuous debugging is not possible because debugger disconnects. .

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How do you know, specifically, that it resets ?

I presume this is when powered via the CN1 ST-Link connector?

Does the USB connection drop?

Have you measured at the STM32 3V supply - is it stable?

Is this a new board, or one that's been previously enjoyed by you and/or others?

[BlueB_Ashutosh]

Yes, the issue happens when board is powered through CN1 ST-Link USB connector.

I suspect reset because:

- Debug session disconnects automatically after around 20–30 seconds.
- STM32CubeProgrammer connection also becomes unstable/disconnects.
- Running application stops during debugging.

I also checked using the 2 user LEDs:

- I set one LED pattern before entering the while loop.
- Inside the while loop, I set a different blinking pattern.
- Initially, after startup, the loop pattern runs correctly.
- But after around 20–30 seconds, LEDs again show the initial startup pattern, which makes me think MCU is resetting/restarting.

I have not yet checked the stability of the STM32 3.3V supply, but USB port connection I checked with multiple port with 2 different laptop.

Yes, this is a new board.

One more observation:
When external 5V and GND are applied, MCU seems to run normally, but COM LED (LED1 red) continuously blinks and LED2 stays ON.

[BlueB_Ashutosh]

Hi, is there any update on this? I am still waiting for your response.

[Ozone]

This update would have to come from you.

There is no know issue with this Discovery board in general, and only you have the board that exhibits this problems.
In addition to checking the power supply, make sure no watchdog is enabled in the code.

And third, try another USB port and/or another PC.

[Andrew Neil]

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@Ozone wrote:

This update would have to come from you.

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Absolutely.

@BlueB_Ashutosh We have no access to your hardware, or your software; we know nothing about you or your setup other than what you post here.

Some good, clear photos would help.

What debugging/tests/investigations have you done to find what's going on?

Try to produce a minimum but complete example which illustrates the issue.

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@Ozone wrote:

try another USB port and/or another PC.

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@BlueB_Ashutosh more things to try here:

https://community.st.com/t5/stm32-mcus/how-to-solve-debugger-connection-issues/tac-p/698105/highlight/true#M956

including with/without hubs, docking stations, etc.