After hours of work I've finally figured out how to make the USB OTG cable work with a Nexus 7 2013 withoyt having to root and instal custom firmware. the trick is to enable developer mode and thats it ........it worked like a champ after that. goto about tablet under settings, at the bottom of the list click Build number 7-8 times then it will say you are now a developer and viola! now when i plug in the usb otg cable with a 3dr radio "I'm using a HK radio clone" it pops up askin you if you want to open droidplanner or andropilot!! I fought with this for over 8 hours today and almost rooted my device over this issue!!