Erastus Coetzee

Important changes to forums and questions

All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.

8 years, 11 months ago.

Disconnecting USB

Does any one know why a 411 reboots when the usb port is disconnected and how to stop it.

1 Answer

Brian Daniels
8 years, 11 months ago.

Hi Erastus,

If you mean the usb port at the top of the Nucleo board, this is where the board gets its power. When the power is removed the F411RE chip will reset.

If you mean the USB controller on the F411RE (not the Nucleo interface), then can you provide more information on what you are you doing and what is happening? Can you post your code and point out the problem area?

Thanks, Brian

Accepted Answer

Hi Brian,

Thanks for the answer. Yes it is the "top" small one used to program the 411. Is it possible to provide this device with power from the 411 asI have and external 5V supply to the 411 board. Regards

I did that and it is working 100%. I checked the order of power up is important. When board has 5V (E) and USB then gets connected it takes the 5V from the 411 and not USB.

Many thanks

posted by Erastus Coetzee 15 Dec 2015

Hi Erastus,

You should be able to power the 411 board through the "VIN" pin located on this page: https://developer.mbed.org/platforms/ST-Nucleo-F411RE/#arduino-compatible-headers

It looks like that pin can accept 5V-9V, so that should keep the board powered.

From your response I wasn't sure if you're already doing this though. If so, are you still seeing the 411 reset when the usb power is removed from the interface?

posted by Brian Daniels 15 Dec 2015