2 years, 4 months ago.

NUCLEO-F401RE keeps blinking red LD1 light

After compiling and flashing my programs onto my board successfully several times, the board suddenly stopped responding out-of-the-blue, instead showing just a slow-blinking red LD1 light. I have my Mini-USB cable properly plugged in to the board and directly into the computer and jumpers set to the following:

  • Both CN2 jumpers are closed.
  • CN11 and CN12 jumpers are closed, but I doubt they have any effect as they just hold spare jumpers.
  • JP1 open.
  • JP5 closed on the U5V side.
  • JP6 closed.

I have swapped out computers and Mini-USB cables as shown below:

  • Microsoft Surface Pro 4 with 64-bit Windows 10 Pro swapped with HP Compaq with 64-bit Windows 7 Enterprise.
  • A total of 4 Mini-USB cables used, I have verified one of the Mini-USB cables to work as files can be read when I plug a digital camera in.

It says in this PDF file under section 6.4: LEDS on page 23/69 the following about LD1:


Slow blinking Red/Off: at power-on before USB initialization

Closing JP1 causes the blinking red LD1 light to turn off but my program still doesn't run.

Any help, possibly a dodgy Micro-USB port on the board?!

1 Answer

2 years, 4 months ago.

Hi Zygarde Team,

We're sorry that you are having problems with your board. Your jumper configuration seems fine. Do you see the board appear as a USB mass storage device? If so, what files are on the drive?

We suggest installing the ST USB driver and/or the ST-LINK firmware:

We hope this gets you up and running again.

-Ralph, Team Mbed

Same problem here. A slow blinking red LED.

The above solution can't work because the USB connection is not set up. With no USB, you don't see mass storage and you can't re-flash ST-Link firmware

posted by Chris Albertson 20 Apr 2019