if your going to a GS2 over serial mb, you need to set the GS2 switch to 232, further you will need to match the port configs the same in both vfd and serial plugin mb.
lastly, you will need to convert the GS2 modbus registers to decimal and address those blocks in the SPMB. Lastly, you can also do "Block" addressing in the GS2 in where you can put all the data in one continous block that you want to control, and/or monitor, then talk to that. Look at the user docs section, read the "Brains users guide", it touches on hooking up modbus stuff.
scott
Commercial Mach3: Screens, Wizards, Plugins, Brains,PLCs, Macros, ATC's, machine design/build, retrofit, EMC2, Prototyping. http://sites.google.com/site/volunteerfablab/