Yes Bernd, thats a good interim approach.
But you’d need to test if the cron job get to the controller.
Currently the firmware update API call doesn’t work from a PC connected via ethernet to your WIFI router, so you’d need a separate PC, turned on all the time, connected to your WIFI router by WIFI, to send the call.
For other lurkers, here are a collection of relevant links I found helpful.
Where Ray suggests resetting the Weather Adjustment percent directly.
https://opensprinkler.com/forums/topic/weather-adjustment-with-interval-program-weather-averaged-over-interval-period/#post-42096
API documentation, choose your version
https://openthings.freshdesk.com/support/solutions/articles/5000716363-os-api-documents
You can find version firmware you’re running on your controller webpage, main menu > about down the bottom e.g. ‘Firmware: 2.8.#’
You have to ‘hash’ your controller password, you did change it from opendoor?, otherwise the local kids will be hacking your front lawn sprinkler to hose the postman.
Zimmerman algorithm equation
https://openthings.freshdesk.com/support/solutions/articles/5000017312-using-weather-adjustments
I’m assuming the algorithm adapts for regions that use celsius, if not, the temperature and rain change parameters needs to be -8% and temp 7.4%, this would be in the code.
Example of the Meteorology Bureau computed weather percentage; WaterWise Santa Barbara, adjusts every week, which I reckon would be fine for most domestic applications.
http://www.waterwisesb.org/
It would need to be scraped from the site or provided as an API by the relevant bureau.
This would be trivial for the Aust. BOM to provide in their agricultural bulletins.
http://www.bom.gov.au/products/IDN65176.shtml