I will probably re-start this thread in the new forum, and maybe add some more detail... However, just some points regarding your post above.... (This could save you some money too !!)
The way I am interfaced to the Zelio, is using the Front Panel Programming port, and the SLin SLout Function blocks inside the Zelio.
From the OpenHAB end, I am using the Exec binding, and an adapted version of a Open-Source C++ program which talks to the Zelio via the front port. All you need, is the programmer cable which came with the Zelio, (and it doesn't matter whether it is the USB cable or Serial version - both work fine....My 'Prod' Zelio has USB, and the test one I have been loaned has a Serial connection). No expensive Zelio Modbus adapter is required. This solution is working just fine.
If you do have the cash burning a hole in your pocket, and you want to interface to the Zelio via that method, I expect the current OpenHAB modbus binding will talk to this, with no modifications required (Just note in the Zelio documentation the limits for the number of Read/Write registers supported on the Zelio Modbus adapter, however if you are using this for light control, you can 'mux/de-mux' a register into Bits within the Zelio FBD, which will easily cover the number of inputs/outputs on a Zelio).
I however raised this topic, as it may be more useful if this was a Native Binding was available for the Zelio (e.g. you don't need to compile a external program, and also have the overhead of executing the program &opening/closing the port everytime you want to read/set status.) Also makes it easy/portable for other users to deploy...
My view however, is that the front panel protocol on the Zelio is pretty-much identical to Modbus ASCII, same read/write command codes, same fields etc however just has an additional word in the address field, so may just need to add an additional "00" in the address field, and perform a corresponding change in the checksumming for the sending/receiving packets....Hence why I thought of the Modbus binding as a starting point.
I probably wont attempt anything until OH2 has been fully released... It looks like the IDE will be easier to setup, and I also have the challenge of learning to spell 'Java' to overcome.... Haven't played much with this language before....