You may have already purchased, so this may be a bit late.
I just replaced my rainBird system with an OSPi (using a Pi version 2). the controller location is in the garage at the farthest point from my wifi access point. My phone normal shows a weak wifi signal there. I didn’t want to wire ethernet out to that spot so I included the wireless internet adapter that Ray sells. It is larger than your normal USB dongle so I was hoping that it would have a lager antenna and make better use of a weak signal.
So far it has worked like a champ. My OSPi has been on the garage wall for the past week and I have not had one comm issue. Pages refresh nice and snappy. I have attached a screen snip that shows my access point’s view of the connection quality.
It is a cool little unit and well worth the $20.
There are a few things that you will need to keep in mind. It connects to OSPi via the ethernet port and the current case is not designed for this so you will need to cut a hole in the case.
Also, both OSPi and the adapter need to maintain the same IP addresses you will need to hard code at least one with a static IP. A DHCP reserve on your router relies on a unique MAC and both OSPi and it’s adapter share the same MAC. The easiest thing here is to leave the Pi on DHCP and hard code the adapter. I hard coded both because i just wanted to learn how to do it on the Pi.
The last thing I can think of here is that the adapter can actually be configured in three different ways. You need Client Mode for this application.