Real engineering and facts for the win!
Interesting use of loading by the slaves to communicate back to the controller. I had seen that in one other design while doing my research.
Also interesting that you did this in all the way back in 2007.
I’m looking at a solution that uses amplitude frequency modulation for bi-directional communications but the use of PWM is just fine also. I think your approach is going to have a lower parts count and lower cost for the valve nodes.
Regarding engaging with commercial manufacturers to develop a standard interface: I don’t expect you’d make much progress on that. It’s in a manufacturer’s best interest to keep a closed system closed. If you look at the prices for commercial two wire systems they are outrageous. That market is ripe for disruption. An open source solution could probably become very popular.
A valve node design that would allow four or eight individual valves to be controlled would be very useful. Lower cost per valve and and many times valves occur in clusters.
Pot those circuit boards in a short piece of PVC pipe and they are ready to go. The controller would make a pice Raspberry Pi hat.
At the end of the day it looks like all you would need for your design is an easy means to program individual valve nodes and your design is ready to go. I imagine the controller could be set up with an interface to do that.
If your design was open sourced it would take off.