This library extends the homie-node-collection to use Relay and Contact nodes with I2C PortExtender
Must use this patch : luebbe/homie-node-collection#5
Or the version from this branch : https://github.com/ivanfmartinez/homie-node-collection/tree/v1.0.2-ifm
The i2c port expander Library : http://blog.iharder.net/2014/08/08/msp430-or-arduino-library-for-pcf8574-i2c-port-expander/