Make RS485Class a constructor arg to ModbusRTUClientClass and ModbusRTUServerClass

[sandeepmistry]

This is an alternative to pull request #11

Instead of having a parameter to begin(...) a new ModbusRTUClientClass or ModbusRTUServerClass instance can be declared with an alternative RS485Class instance.

[nud]

What about going even further and calling it "transport" rather than "rs485"? I myself would very much like to have a RS232 transport as well.

[sandeepmistry]

@nud that's a good suggestion! I didn't know RTU also supported RS232.

Have you tested this pull request?

Would you be update for adding RS232 support? Let me know, we can merge this one and you can submit another pull request for it.

[willwilder]

Have you had success getting this to work? I have a use case for specifying the hardware serial port I want to use, trying to get the Sparkfun AST-CAN485 running as a ModbusRTU slave. The RS-485 chip is hard wired to Serial1.

[ADCTechnologyGroup01]

I'd also like to see the interface abstracted from the protocol. For use with RS232 and also the native USB Serial Port (which is typically only used for debugging with "Serial Monitor").

[cheetor5923]

I like this idea... Realistically the best option would be to have each layer of the OSI model as a separate modular bit of code.

[SWoto]

@sandeepmistry, I've tested your code with the KitchenSink's example, ModbusRTUServerKitchenSink and ModbusRTUClientKitchenSink.

Steps:

1. Download your commit - ea16c79920ec62cc96d1c0ca8be973d8cb853559
2. Change Serial port

[...] some code before here 

RS485Class _RS485(Serial2, txPin, dePin, rePin);

void setup() {
  ModbusRTUClient = ModbusRTUClientClass(_RS485);

[...] some code after here 

3. Run Server in one board and client in another.

Results:

16:17:10.627 -> Writing Coil values ... success
16:17:10.667 -> Reading Coil values ... success
16:17:10.667 -> 0 0 0 0 0 0 0 0 0 0 
16:17:10.667 -> Reading Discrete Input values ... success
16:17:10.708 -> 0 0 0 0 0 0 0 0 0 0 
16:17:10.708 -> Writing Holding Registers values ... failed! Connection timed out
16:17:11.715 -> Reading Input Register values ... failed! Connection timed out
16:17:12.717 -> Reading input register values ... failed! Connection timed out
16:17:18.754 -> 
16:17:18.754 -> Writing Coil values ... success
16:17:18.754 -> Reading Coil values ... success
16:17:18.787 -> 1 1 1 1 1 1 1 1 1 1 
16:17:18.787 -> Reading Discrete Input values ... success
16:17:18.787 -> 1 1 1 1 1 1 1 1 1 1 
16:17:18.787 -> Writing Holding Registers values ... failed! Connection timed out
16:17:19.840 -> Reading Input Register values ... failed! Connection timed out
16:17:20.840 -> Reading input register values ... failed! Connection timed out

If I turn the Server off, I get all the results as Connection timed out, so they are communicating.

I've also changed Serial2 to Serial3 and I also receive Connection timed out every time, so the modification worked just fine.

Sugestion

Would be really good to have this option in the ModbusRTUServer too.

[SWoto]

@sandeepmistry, please let me know if there are any other tests that you would like me to run.

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[SWoto]

This branch is working like a charm.

RS485 = RS485Class(Serial2, Serial2, txPin, dePin, rePin);
ModbusRTUClient = ModbusRTUClientClass(_RS485);

Solves the problem that the RS485 class is hardcoded in the ArduinoModbus.

@sandeepmistry