Put simply, BlinkUp is a process to transmit your wireless network's SSID (name) and encryption key (password) to your Rachio controller (Gen1) so that it can get online.
BlinkUp transmits the information to the Gen1 optically by rapidly flipping a mobile device’s screen between maximum and minimum brightness at a fixed rate. A photosensor on the Gen1 reads the data and uses it first to connect to the Internet and then to seek authorization to access cloud based servers.
BlinkUp in Action*
A step by step walkthrough of how to replace your current irrigation controller with a Rachio Generation 1 and connect it to your home's WiFi.
* For blinkup tips, please watch the video from 2:00-3:20