I am using QGC with PX4. I had a doubt reagrding ESC calibration using the power tab in QGC which has the ESC calibration option. The problem is whenever i try to calibrate the QGC message just says err about the battery being not connected even though all ESCs are on and the tone comes. Could you please help me regarding this? Also connecting the PX4 from battery and also from USB will it burn the board or the board has internal circuitry to reject the power coming from 2 sources?