Does the Edimax Nano work with the latest BBB Debian OS? If so, you can follow the instructions here to install the OpenSprinkler Unified Firmware:
https://opensprinkler.freshdesk.com/solution/categories/5000027039/folders/5000149652/articles/5000631599-installing-and-updating-the-unified-firmware
The pre-configured SD card is based on an old version of kernel so it may not support the latest Edimax dongle.