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. See also Modbus/include/mb.h for instructions on how to initialize and begin to use an instance of FreeModbus stack in given program. Also mention that eMBPoll() routine may be set up as a task in an RTOS, to realize the periodic polling which is part of the stack's runtime manifestation . . .

Looks like also this function to register callbacks for end-user-device-specific Modbus registers will be important:

  eMBErrorCode eMBRegisterCB ( UCHAR ucFunctionCode,
    pxMBFunctionHandler pxHandler
  )