Midi controller keyboard connection problem

[Norman Austin]

I'm trying to connect my Alesis VX49 MIDI controller keyboard to my iPad Air2 via the camera connection kit using a standard USB cable. I have separate power supplies to both the iPad and the VX49, but the iPad tells me it cannot connect to the VX49 because the power drain is too much. Obviously it's not too much as I have a separate power supply connected.

Does anyone know a workaround for this problem? I wish to control soft-synths on the iPad using the VX49 keyboard so I simply want the iPad to recognize midi information.