Defined modbus errors as custom error objects that can be used as needed by both the rtu and tcp functions. Also started revamping the rtu access logic to be more in line with the tcp version (i.e., with its own data frame struct and access methods based on that struct) -- still in progress.
Revamped the RTU logic to function with its associated RTUFrame object, consistent with the TCP/IP component redesign (RTU version yet to be tested versus a real device, but coming soon)