I have 2 arduinos (for now will be adding more) connected using I2C. I have a Master reader and slave writer. I am using the Slave to tell me the Master when a function is called. I have a web server off the master with a checkbox whether that function has been called. I am have the code to read the checkbox being unchecked or checked. I want to trigger a relay connected to my slave through my webserver checkbox connect to the Master.
I am lost how to send data from the master reader to the slave to trigger a fuction