Questions about GetPublicKey and Xpub.

Hello,
  I've implemented an extension to trezor-android that exposes a few of the Message types and provides a default handler for Trezor responses.  This comes with an interface for two GUI callbacks, PinMatrix and Passphrase.

I've hit a wall trying to fetch the PublicKey(s) in Xpub format.

Things to note:
1. This is my first attempt a Java, let me know if I'm doing something wrong.
2. I don't understand the mathematics involved.  If there is a reference that would help me understand the  HDNodeType better that just may answer my question.

What I expect is to read or construct a BIP32 Deterministic Key Generator's Derived Public Key as one would use on http://bip32.org/'s JavaScript example.  When I plug one of these into BIP32 Extended Key I'm able to clearly demonstrate how to build a list of Bitcoin Addresses.

If I'm not mistaken this is the same key provided by mytrezor.com's log, listed under "Subscribing".

The current goal is to probe a Trezor device and populate "something like" myTREZOR Lite, instead of scanning the code with the electronic eye or entering it with the keypad.

Cheers!