u need a DUAL USB power cable to help power the hard drive becauze the AMPs coming out from the Ipad was reduced, i got it to work plugging 1 end into wall charger and the other usb into the ipad.
its a bit complicated since it will not auto mount, you need mobile terminal and manually mount/unmount everytime u use it.
(forgot to add, it will only read FAT32 hard drives.
there is a youtube video on the whole process. but he uses a laptop to ssh into it, u can use mobile terminal instead without the laptop.