OpenEVSE Integration to existing system

My existing PV system with about 18kWh of hot water energy storage has worked extremely well since 2012.

Now that I have an EV on order I am thinking about some more PV panels and adding car charging as an additional load to the system.

I have constructed and installed an openevse unit and I can modify the master diverter to add another load control.

My problem is that currently the PV diverter cannot communicate with the openevse unit.

I am looking for advice on which route to pursue to integrate the various components.