Create an application to communicate with a water pump controller using MODBUS over RS-485

I have an L922/S dual pump controller that I want to manage via a desktop application using MODBUS over an RS-485 connection. I am using a USB to RS-485 adapter. I need to be able to read and write to registers in the controller and thereby remotely monitor and manage the operation of the controller. This will involve interpreting the register data to understand operating voltages, current consumption, and various other operating parameters. I also need to set the automatic pump start and stop levels and also be able to manually manage the pumps. I am currently able to read some data (holding Registers) using the RADZIO MODBUS master emulator but require more detailed interpretation of the data returned from the controller. I am unable to write to the controller using the emulator but that is probably to to a lack of understanding of the MODBUS protocol. The controller comes with a wired RS-495 remote controller that has the same functions as the main panel seen on the controller - Just google L922/S for some more background on the controller.