Q:

How to communicate with USB protocol for an MFI accessory

I have bought an iSpread (http://www.photofast.tw/iFlashDrive2013_1.html?pid=132) which allows me to put files on it via USB on my PC.  Now those files on the USB I would like to transfer to my iPad.  I know that there is an application for that developed by the creators of the iSpread but for an application I'm creating I would need this integrated into my own application. 
I have downloaded the EADemo application and installed it on my iPad.  There I can see that the accessory is attached and that it uses the tw.photofast.cr protocol. 
How do I get a list of the files and transfer them?  I assume that since this USB works on my PC that it uses a standard USB protocol.  I'm able to send strings and hex data to the accessory using the EADemo application but no bytes are received. 
Anyone have experience with this? 

A:

You'll need to know the protocol their app uses to communicate with the accessory. 
They might give it to you, if you indicate you're willing to sign an NDA and they think they can benefit from the transaction.  Some hardware manufacturers offer an SDK in the form of a static library.  
If you really wanted to try to reverse engineer it, a good start would be to jailbreak your phone and run their app with gdb attached so you can poke around. 