added methods to configure modbus server to existing data stuctures

[ASolchen]

With memory being tight on most micro controllers, I felt like I shouldn't have to allocate memory for modbus to use, but instead point the server at existing data structures. If the structures are not of the same type, the user can cast it as such.

[github-actions[bot]]

Memory usage change @ f53379ab577d793f9a9923aaef3543795d84bf8b

Board	flash	%	RAM for global variables	%
arduino:avr:leonardo	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:avr:nano	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed:envie_m7	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed:nano33ble	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board|examples/RTU/ModbusRTUClientKitchenSink
flash|%|examples/RTU/ModbusRTUClientKitchenSink
RAM for global variables|%|examples/RTU/ModbusRTUClientToggle
flash|%|examples/RTU/ModbusRTUClientToggle
RAM for global variables|%|examples/RTU/ModbusRTUServerKitchenSink
flash|%|examples/RTU/ModbusRTUServerKitchenSink
RAM for global variables|%|examples/RTU/ModbusRTUServerLED
flash|%|examples/RTU/ModbusRTUServerLED
RAM for global variables|%|examples/RTU/ModbusRTUTemperatureSensor
flash|%|examples/RTU/ModbusRTUTemperatureSensor
RAM for global variables|% -|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|- arduino:avr:leonardo|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0 arduino:avr:nano|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0 arduino:mbed:envie_m7|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0 arduino:mbed:nano33ble|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0|0|0.0

Click for full report CSV

``` Board,examples/RTU/ModbusRTUClientKitchenSink
flash,%,examples/RTU/ModbusRTUClientKitchenSink
RAM for global variables,%,examples/RTU/ModbusRTUClientToggle
flash,%,examples/RTU/ModbusRTUClientToggle
RAM for global variables,%,examples/RTU/ModbusRTUServerKitchenSink
flash,%,examples/RTU/ModbusRTUServerKitchenSink
RAM for global variables,%,examples/RTU/ModbusRTUServerLED
flash,%,examples/RTU/ModbusRTUServerLED
RAM for global variables,%,examples/RTU/ModbusRTUTemperatureSensor
flash,%,examples/RTU/ModbusRTUTemperatureSensor
RAM for global variables,% arduino:avr:leonardo,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0 arduino:avr:nano,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0 arduino:mbed:envie_m7,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0 arduino:mbed:nano33ble,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0 ```

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[nsted]

Thanks for this PR. I've been using it and loving it.

[ASolchen]

Thanks for the feedback. Happy to help!

On Wed, Jun 2, 2021, 08:46 Nicholas Stedman @.***> wrote:

Thanks for this PR. I've been using it and loving it.

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[ASolchen]

I've tried signing the CLA several times. It still shows "not signed yet."

[per1234]

It still shows "not signed yet."

Hi @ASolchen. Thanks so much for your pull request. The problem with the CLA is that the commit is by @testtechsolutions, not by your @ASolchen user. The email address of the user signing the CLA must match to that of the author of the commit.

[per1234]

Closing in favor of https://github.com/arduino-libraries/ArduinoModbus/pull/73, which is this proposal but with the CLA fixed. Thanks @ASolchen!