I believe it should be possible to use the RTU protocol, however it will take a significant re-work of the code that you are ref...
Answered 4 years ago
Modbus RS-232 ASCII serial communication with a Programmable Logic Controller (PLC)
5 years ago
3 years ago
Functions for communicating with Gilson GSIOC protocol devices over RS-232
Longitudinal Redundancy Check (LRC) for Modbus PLC Controllers using ASCII
7 years ago