You are reading a single comment by @user66772 and its replies.
Click here to read the full conversation.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@user66772
I think I'm going to answer my own question...
Pin A9 of the on-board STM32 microcontroller is always connected to the fused USB 5V voltage reference.
The digitalWrite function essentially connects the USB voltage pin to GND, thus creating a short circuit on the USB port. This means there is no longer power going to the board AT ALL. It has been "disconnected".
bows