Modbus notes

• https://en.wikipedia.org/wiki/Modbus

• https://www.embedded-solutions.at/en/freemodbus/freemodbus-examples/

• https://libmodbus.org/ . . . Ubuntu package is 'libmodbus5' and 'libmodbus-dev'

- 2019-11-08 FRI -

When working with FreeModbus, be sure to pay attention to the versions of protocol available, and likely, we only want to enable one of these. See Modbus/include/mbconfig.h.