Can the Spark Core be powered from 3.3V? That is, connect 3.3V to the 3V3 pin.
Have a look 
http://docs.particle.io/core/start/#pins
Can the Spark Core be powered from 3.3V? That is, connect 3.3V to the 3V3 pin.
Have a look 
http://docs.particle.io/core/start/#pins