I need an MQTT interface into Openhab 2. My plan is to build a gateway which consists of a Moteino with onboard RFM69 module. Interface between the radio and the AVR is via SPI. This still frees up the I2C interface to allow interfacing to an ethernet connected Arduino. The Moteino will grab the data from over the air, package it into a structure and send it out the I2C. Moteino incoming I2C packets will be formatted for transmission on the RFM69 radio. On the ethernet Arduino the received data structure will be converted and published as an MQTT packet to the MQTT broker.

An Arduino with ethernet shield will provide the ethernet half of the gateway instead of a Huzzah.

The Gateway was implemented using a Moteino for Davis wireless intercept to decode data. A receiving Huzzah hanging onto the Moteino serial line takes the raw data and converts it to MQTT packets as well as periodic Wundergroung uploads.