The OpenSprinkler firmware user manual is on our support website:
https://openthings.freshdesk.com/support/home
The device password is by default opendoor unless if you have changed it. If you don’t remember anymore, you can use the on-board buttons to set the controller to ignore password. The firmware user manual explains how.
If you have OpenSprinkler Pi, there are no buttons you can use to reset the password. Unfortunately there you will have to ssh to your RPi, or connect it to a keyboard and monitor, and delete the configurations files to trigger a factory reset. You can, however, save your configuration files to a different folder in order to recover settings later.