Without seeing what code you are uploading and what you are trying to do it would all be guess work.
What you are seeing is a core dump - something is causing the board to panic.
@Wilberforce started
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.
Without seeing what code you are uploading and what you are trying to do it would all be guess work.
What you are seeing is a core dump - something is causing the board to panic.