STM32F407VGT6 – LD1 LED stays Green when plugging USB, not turning Red

[Adi3]

Hello,

I am using an STM32F407VGT6 board with the ST-LINK debugger.
When I plug the USB cable into the board, the LD1 LED on the ST-LINK stays Green and does not turn Red.

From what I understand:

Green LED indicates that ST-LINK is powered and idle.

Red LED should appear during debugging or when an error occurs.

However, in my case the LED always remains Green.

My questions:

Why does LD1 remain Green when I connect the board?

Under what conditions does LD1 turn Red?

Does a constant Green LED indicate that the MCU is stuck (for example in HardFault or reset)?

I am using STM32CubeIDE for programming and debugging.

Any guidance would be appreciated.

Thank you.

[Andrew Neil]

Welcome to the forum.

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

In particular:

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@Adi3 wrote:

I am using an STM32F407VGT6 board with the ST-LINK debugger.

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What board are you using ?

Is it the STM32F407G-DISC1 ?

[AScha.3]

Hi,

so does it work ?  debug etc ?

btw

On my F407 board the green LD1 is also always on, after connect to USB/PC.

[Gyessine]

Hello @Adi3 

>Why does LD1 remain green when I connect the board?

LD1 remains green to indicate that communication is in progress between the PC and the ST-LINK/V2-A.

>Does a constant green LED indicate that the MCU is stuck, for example, in HardFault or reset?

In debug mode, LD1 should blink. If LD1 remains green, it likely means that the connection is lost, possibly due to a loose cable or a faulty USB port. If this occurs, unplug the board, reconnect it, and start a new debug session.

To better understand the ST-LINK LED behavior, consult section 7.3 and 7.5 of the board  user manual.
BR
Gyessine