I'd definitely suggest you power SIM800 from a LiPo battery. I have never been able to get a SIM800 to work properly when just powered off USB - I think it just draws too much power.
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.
I'd definitely suggest you power SIM800 from a LiPo battery. I have never been able to get a SIM800 to work properly when just powered off USB - I think it just draws too much power.