OpenSprinkler › Forums › OpenSprinkler Unified Firmware › 2.1.6 is the latest, but it will only let me install 2.1.5 (h/w v2.1u) › Reply To: 2.1.6 is the latest, but it will only let me install 2.1.5 (h/w v2.1u)
You are correct that you can’t upgrade OS 2.1 to firmware 2.1.6 through USB any more. This is explained in this support article:
We do provide firmware upgrade service free of charge. Alternatively, we provide discounted price for OS 2.1 owners to upgrade to OS 2.3.