See this other thread:
Today is a big day, because the source tree with FreeRTOS, a full tcp/ip stack and the particle cloud-interface code is publicly available. This is the ideal vehicle for the cheapest wired core, based on the '207 chip.
I strongly suggest that everyone interested in working on the wired core begin by cloning the repo and building firmware for either the core or the photon as a baseline. I know that Mat is working on docs to explain the build process, so don't jump on him for lack of docs right away.
I have device ID and USB PIDs allocated for a wired core, I'll be checking that in real-soon-now (tm).