Nucleo L010RB USART working only if you plug the USB

[JAgue.1]

Hi,

I'm working on a nucleo L010RB board, i wanted to test my application on battery supply but the USART2 didn't work without the usb ST-LINK so i assumed that the USART3 would work but it's the same problem.

When I start the nucleo with only battery the nucleo seems to start up right (I am making the user led blinking in the program loop.) but I don't receive any prompt on my uart and as soon I plug the usb I start getting all messages.

I am assuming that there is something with ST-LINK waiting to be link with a computer.

PS: I correctly put the JP5 on E5V.

Thanks for the help.

J

[JTP1 · Accepted solution]

Hello

You dont give very much info about your connections, but maybe your ground is missing from mcu to pc (some usb/uart adapter ?). And when you hook up stlink, grounds connect that way.

Or how you receive the uart communication ?

Br J.T 

[JAgue.1]

Thanks,

Your guess was right. I had to plug the ground to my usb/uart adapter.