So here are links that are relavant to the device I am working with:
Here is a link to the communication manual specific to this family of embedded Ethernet devices (iSeries Monitor/Controller)
Here is a link to the communication manual for the temp humidity controller itself:
Finally a link to the iServer manual that covers details like wiring for RS 485 or RS 232 as well as the details of the iServer web interface
Getting right to modbus data mappings, from the iTH manual (second link) page 12 there is a bit that says that these devices operate using the RTU transmission mode -
So I would expect that means I should be using the modbus rtu over TCP driver.
Next i get details about how the message frames are constructed including details about CRC checking - I can only assume this is all handled under the hood of the RTU TCP driver.
Now the good stuff, page 15 has the modbus registers and the function codes supported - I expect to need the following:
01 SETPOINT 1
02 SETPOINT 2
27 RH% VALUE
28 TEMP. VALUE
29 DEWPOINT VALUE (edit - i actually don’t need this value at all since it can be calculated from the other two)
There are some other details in the manual about setting the device to modbus mode using the panel interface - going to give that a try and see what happens with these address mappings