Thank you Derek for your detailed write-up, which continues to be helpful 2 years later. The exclusive virtual network tip (which I wouldn’t have thought to try) aptly solved my connectivity problem!
Out of the box, my OpenSprinkler 3 (OS 3.0 AC) was unable to hold wifi connectivity. I had also ordered ethernet adapter just in case, but wired ethernet was unable to hold connection either. I was limping along having to power-cycle just to get fleeting, bare minimum connectivity. I set up OS 3.0 to be solo client on its own (wifi) virtual network (Asus router with Tomato firmware) and connectivity problems solved. As noted, this is an advanced network set-up, but can be helpful work-around for those well versed in router set-up.
I have done a bunch of RPi and Arduino projects, and am very appreciative of this product. It really serves my needs. THAT SAID, I would urge Ray to migrate the OS 3x product to a more stable/performant platform so that the non-nerds aren’t pulling their hair out over something (connectivity) that should be a given. I see 64-bit SBC boards with built-in Arduino microcontroller, so 32-bit options should be pretty affordable/doable. Time to leave 8-bit behind (or warn buyers that connectivity is “hobby” quality).