Hi
there are treads talking about John Deere valves, some of them needs modifications in the arduino code.
pid-for-danfoss-proportional-valve
jd-8230-hydraulic-steering
For the motor/valve driver I prefer the cytron MD13S.
Are you planning always using AOG or only when the JD already in use?
You will also need a wheel angle signal, probably you can take signal from the OEM in differential mode.
For a clean install with a hydraulic valve you should use the steering wheel encoder to cut off the valve. I don’t know if you can simply tap in to use the signal.
If you want use both AOG and JD I think it is possible to use the oem valve if you can switch the leads from one system to the other.
I will follow is tread, I will maybe install an RTK AOG on a JD6430 that run with a Starfire 3000 with SF1/SF2 most of the time. AOG for steering and JD for mapping.