Let me start letting you know that I am amazed by this device. The Raspberry Pi Zero W is a very small computer running Raspian. That may suffice to convince you of what it can do. Raspberry Pi Zero W (down) compared
As mentioned in a previous post, I turned a Raspberry Pi into am Openflow LINC switch. Nevertheless, I was not able to connect it to a Ryu controller on an external machine. I even installed Ryu into another Rasbperry Pi
You may find this information in several blogs, specially the useful thread published by Steve Roberts on his blog. In this short post I plan to update some of the procedures to 2016 standards. That is, current builds and packages.