De-hardcoded RS485Class object to be used by modbus.

[psmay]

This proposed change makes it possible to use an RS485Class object other than the default RS485 with the contained libmodbus. This is useful with boards with multiple serial ports or when the user wants to specify different DE/RE pins.

[sandeepmistry]

Hi @psmay,

Thanks for opening this pull request!

I'm curious about your use case, do you need multiple RS485 interfaces at the same time? I'm wondering if another option is to add something like RS485.setSerial(...).

[psmay]

This change is for supporting these use cases:

1. Modbus-RTU on a single serial port that does not match the default RS485 configuration, without manually modifying the ArduinoRS485 and ArduinoModbus sketches.
   • For example, I might have a client sketch which uses RS485Class ourRS485(Serial1, PB6, PB9, PB8); and a different server sketch that uses RS485Class ourRS485(Serial2, PA2, PA3, PA4);. Before this change, I would have needed to maintain a custom ArduinoRS485 and ArduinoModbus libraries for each.
2. Modbus-RTU on multiple serial ports in the same sketch.
   • I haven't tested that this PR addresses this entire use case, but it does include groundwork that would be necessary for this support.

[sandeepmistry]

Hi @psmay,

Thank you for the explanation. What do you think about making the RS485Class a constructor argument instead of a parameter to begin? I've prepared pull request #14 for this change.

[pruwait]

How can I Use Serial1 or Serial2 with library?

[SWoto]

@pruwait , probably the only way to currently change the Serial being used is by changing it on RS485.cpp.

RS485Class RS485(SERIAL_PORT_HARDWARE, RS485_DEFAULT_TX_PIN, RS845_DEFAULT_DE_PIN, RS845_DEFAULT_RE_PIN);

To (example)

RS485Class RS485(Serial2, RS485_DEFAULT_TX_PIN, RS845_DEFAULT_DE_PIN, RS845_DEFAULT_RE_PIN);

Also, you can check pins_arduino.h file and find the alias for Serial2, it will probably be something like SERIAL_PORT_HARDWARE2, so you will have:

RS485Class RS485(SERIAL_PORT_HARDWARE2, RS485_DEFAULT_TX_PIN, RS845_DEFAULT_DE_PIN, RS845_DEFAULT_RE_PIN);

[per1234]

Superseded by #59