Depending on what is on the Arduino side, I may have some specific advice (very specific if it's an AVR - I know exactly what's needed in this case.)
@DrAzzy 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.
Depending on what is on the Arduino side, I may have some specific advice (very specific if it's an AVR - I know exactly what's needed in this case.)