You are reading a single comment by @Andrea 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.
Andrea
...no surprise that there are serial communication issues...
From the pic I do only see RX and TX to TX and RX connections and no ground wire between the two boards... For serial communication the pins are floating and TX and RX even interfere with each other...
Get a GND to GND wire in and it should work like a charm... (I would put a - Signal- GND wire in even when both are powered by the same source - battery or USB from what ever - and have common/some Ground from power Ground (neg rail).